diff --git a/schema/alter-table-log.txt b/schema/alter-table-log.txt
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@@ -0,0 +1,1744 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+This file contains a log of ALTER TABLE statements that need to be executed
+to bring a Monorail SQL database up to the current schema.
+
+================================================================
+2012-05-24: Added more Project fields.
+
+ALTER TABLE Project ADD COLUMN read_only_reason VARCHAR(80);
+ALTER TABLE Project ADD COLUMN issue_notify_address VARCHAR(80);
+ALTER TABLE Project ADD COLUMN attachment_bytes_used INT DEFAULT 0;
+ALTER TABLE Project ADD COLUMN attachment_quota INT DEFAULT 52428800;
+ALTER TABLE Project ADD COLUMN moved_to VARCHAR(250);
+ALTER TABLE Project ADD COLUMN process_inbound_email BOOLEAN DEFAULT FALSE;
+
+================================================================
+2012-06-01: Added inbound_message for issue comments
+
+ALTER TABLE Comment ADD COLUMN inbound_message TEXT;
+
+
+================================================================
+2012-06-05: Removed send_notifications_from_user because Monorail will
+not offer that feature any time soon.
+
+ALTER TABLE ProjectIssueConfig DROP COLUMN send_notifications_from_user;
+
+
+================================================================
+2012-06-05: Add initial subscription options.
+
+ALTER TABLE User2SavedQuery ADD COLUMN subscription_mode
+    ENUM ('noemail', 'immediate') DEFAULT 'noemail' NOT NULL;
+
+
+================================================================
+2012-07-02: Revised project states and added state_reason and delete_time
+
+ALTER TABLE Project MODIFY COLUMN state ENUM ('live', 'archived', 'deletable')
+NOT NULL;
+
+ALTER TABLE Project ADD COLUMN state_reason VARCHAR(80);
+ALTER TABLE Project ADD COLUMN delete_time INT;
+
+
+================================================================
+2012-07-05: Added action limits and dismissed cues
+
+CREATE TABLE ActionLimit (
+  user_id INT NOT NULL AUTO_INCREMENT,
+  action_kind ENUM (
+      'project_creation', 'issue_comment', 'issue_attachment',
+      'issue_bulk_edit'),
+  recent_count INT,
+  reset_timestamp INT,
+  lifetime_count INT,
+  lifetime_limit INT,
+
+  PRIMARY KEY (user_id, action_kind)
+) ENGINE=INNODB;
+
+
+CREATE TABLE DismissedCues (
+  user_id INT NOT NULL AUTO_INCREMENT,
+  cue VARCHAR(40),  -- names of the cue cards that the user has dismissed.
+
+  INDEX (user_id)
+) ENGINE=INNODB;
+
+
+ALTER TABLE User ADD COLUMN ignore_action_limits BOOLEAN DEFAULT FALSE;
+
+================================================================
+2012-07-11: No longer using Counter table.
+
+DROP TABLE Counter;
+
+================================================================
+2012-09-06: Drop AttachmentContent, put blobkey in Attachment
+and drop some redundant columns.
+
+Note: This loses attachment data that might currently be in your
+instance. Good thing these schema refinements are getting done
+before launch.
+
+ALTER TABLE Attachment DROP COLUMN attachment_id;
+ALTER TABLE Attachment DROP COLUMN comment_created;
+ALTER TABLE Attachment ADD COLUMN blobkey VARCHAR(1024) NOT NULL;
+
+DROP TABLE AttachmentContent;
+
+ALTER TABLE IssueUpdate  DROP COLUMN comment_created;
+
+
+================================================================
+2012-11-01: Add Components to IssueUpdate enum.
+
+alter table IssueUpdate modify field ENUM ('summary', 'status', 'owner',
+'cc', 'labels', 'blockedon', 'blocking', 'mergedinto', 'project',
+'components') NOT NULL;
+
+
+================================================================
+2012-12-10: Add template admins and field admins
+
+
+CREATE TABLE FieldDef2Admin (
+  field_id INT NOT NULL,
+  admin_id INT NOT NULL,
+
+  PRIMARY KEY (field_id, admin_id),
+  FOREIGN KEY (field_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (admin_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+CREATE TABLE Template2Admin (
+  template_id INT NOT NULL,
+  admin_id INT NOT NULL,
+
+  PRIMARY KEY (template_id, admin_id),
+  FOREIGN KEY (template_id) REFERENCES Template(id),
+  FOREIGN KEY (admin_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+================================================================
+2012-12-14: Add a table of custom field values
+
+ALTER TABLE FieldDef MODIFY field_type ENUM (
+  'enum_type', 'int_type', 'str_type', 'user_type') NOT NULL;
+
+CREATE TABLE Issue2FieldValue (
+  iid INT NOT NULL,
+  field_id INT NOT NULL,
+
+  int_value INT,
+  str_value VARCHAR(1024),
+  user_id INT,
+
+  derived BOOLEAN DEFAULT FALSE,
+
+  INDEX (iid, field_id),
+  INDEX (field_id, int_value),
+  INDEX (field_id, str_value),
+  INDEX (field_id, user_id),
+
+  FOREIGN KEY (iid) REFERENCES Issue(id),
+  -- FOREIGN KEY (field_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+================================================================
+2012-12-18: persistence for update objects on custom fields
+
+ALTER TABLE IssueUpdate MODIFY field ENUM (
+  'summary', 'status', 'owner', 'cc', 'labels', 'blockedon', 'blocking', 'mergedinto',
+  'project', 'components', 'custom' ) NOT NULL;
+
+ALTER TABLE IssueUpdate ADD custom_field_name VARCHAR(255);
+
+
+================================================================
+2012-12-27: Rename component owner to component admin
+
+DROP TABLE Component2Owner;
+
+CREATE TABLE Component2Admin (
+  component_id SMALLINT UNSIGNED NOT NULL,
+  admin_id INT NOT NULL,
+
+  PRIMARY KEY (component_id, admin_id),
+
+  FOREIGN KEY (component_id) REFERENCES ComponentDef(id),
+  FOREIGN KEY (admin_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+================================================================
+2013-01-20: add field applicability predicate
+
+ALTER TABLE FieldDef ADD applicable_type VARCHAR(80);
+ALTER TABLE FieldDef ADD applicable_predicate TEXT;
+
+================================================================
+2013-01-25: add field validation details
+
+ALTER TABLE FieldDef ADD max_value INT;
+ALTER TABLE FieldDef ADD min_value INT;
+ALTER TABLE FieldDef ADD regex VARCHAR(80);
+ALTER TABLE FieldDef ADD needs_member BOOLEAN;
+ALTER TABLE FieldDef ADD needs_perm VARCHAR(80);
+
+
+================================================================
+2013-02-11: add grant and notify to user-valued fields
+
+ALTER TABLE FieldDef ADD grants_perm VARCHAR(80);
+ALTER TABLE FieldDef ADD notify_on ENUM ('never', 'any_comment') DEFAULT 'never' NOT NULL;
+
+
+================================================================
+2013-03-17: Add Template2FieldValue
+
+CREATE TABLE Template2FieldValue (
+  template_id INT NOT NULL,
+  field_id INT NOT NULL,
+
+  int_value INT,
+  str_value VARCHAR(1024),
+  user_id INT,
+
+  INDEX (template_id, field_id),
+
+  FOREIGN KEY (template_id) REFERENCES Template(id),
+  -- FOREIGN KEY (field_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+================================================================
+2013-05-08: eliminated same_org_only
+
+-- This needs to be done on all shards.
+UPDATE Project SET access = 'members_only' WHERE access = 'same_org_only';
+ALTER TABLE Project MODIFY COLUMN access ENUM ('anyone', 'members_only');
+
+================================================================
+2013-05-08: implemented recent activity timestamp
+
+-- This needs to be done on all shards.
+ALTER TABLE Project ADD recent_activity_timestamp INT;
+
+================================================================
+2013-07-01: use BIGINT for Invalidate timesteps
+
+ALTER TABLE Invalidate MODIFY COLUMN timestep BIGINT NOT NULL AUTO_INCREMENT;
+
+
+================================================================
+2013-07-23: renamed to avoid "participant"
+
+RENAME TABLE ParticipantDuty TO MemberDuty;
+RENAME TABLE ParticipantNotes TO MemberNotes;
+
+================================================================
+2013-08-22: renamed issue_id to local_id
+
+-- On primary and all shards
+ALTER TABLE Issue CHANGE issue_id local_id INT NOT NULL;
+
+-- On primary only
+ALTER TABLE IssueFormerLocations CHANGE issue_id local_id INT NOT NULL;
+
+================================================================
+2013-08-24: renamed iid to issue_id
+
+-- On primary and all shards
+
+ALTER TABLE IssueSummary DROP FOREIGN KEY IssueSummary_ibfk_1;
+ALTER TABLE IssueSummary CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE IssueSummary ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE Issue2Label DROP FOREIGN KEY Issue2Label_ibfk_1;
+ALTER TABLE Issue2Label CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Issue2Label ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE Issue2Component DROP FOREIGN KEY Issue2Component_ibfk_1;
+ALTER TABLE Issue2Component CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Issue2Component ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE Issue2Cc DROP FOREIGN KEY Issue2Cc_ibfk_1;
+ALTER TABLE Issue2Cc CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Issue2Cc ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE Issue2Notify DROP FOREIGN KEY Issue2Notify_ibfk_1;
+ALTER TABLE Issue2Notify CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Issue2Notify ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE IssueStar DROP FOREIGN KEY IssueStar_ibfk_1;
+ALTER TABLE IssueStar CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE IssueStar ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE IssueRelation DROP FOREIGN KEY IssueRelation_ibfk_1;
+ALTER TABLE IssueRelation CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE IssueRelation ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE IssueRelation CHANGE dst_iid dst_issue_id INT NOT NULL;
+
+ALTER TABLE Issue2FieldValue DROP FOREIGN KEY Issue2FieldValue_ibfk_1;
+ALTER TABLE Issue2FieldValue CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Issue2FieldValue ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+-- On primary only
+ALTER TABLE Comment DROP FOREIGN KEY Comment_ibfk_2;
+ALTER TABLE Comment CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Comment ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE Attachment DROP FOREIGN KEY Attachment_ibfk_1;
+ALTER TABLE Attachment CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE Attachment ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+ALTER TABLE IssueUpdate DROP FOREIGN KEY IssueUpdate_ibfk_1;
+ALTER TABLE IssueUpdate CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE IssueUpdate ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+-- I was missing a foreign key constraint here.  Adding now.
+ALTER TABLE IssueFormerLocations CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE IssueFormerLocations ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+-- I was missing a foreign key constraint here.  Adding now.
+ALTER TABLE ReindexQueue CHANGE iid issue_id INT NOT NULL;
+ALTER TABLE ReindexQueue ADD FOREIGN KEY (issue_id) REFERENCES Issue(id);
+
+
+================================================================
+2013-08-30: added per-project email sending flag
+
+-- On primary and all shards
+ALTER TABLE Project ADD COLUMN deliver_outbound_email BOOLEAN DEFAULT FALSE;
+
+
+================================================================
+2013-10-30: renamed prompts to templates
+
+ALTER TABLE ProjectIssueConfig
+CHANGE default_prompt_for_developers default_template_for_developers INT NOT NULL;
+
+ALTER TABLE ProjectIssueConfig
+CHANGE default_prompt_for_users default_template_for_users INT NOT NULL;
+
+ALTER TABLE Template
+CHANGE prompt_name name VARCHAR(255) NOT NULL,
+CHANGE prompt_text content TEXT,
+CHANGE prompt_summary summary TEXT,
+CHANGE prompt_summary_must_be_edited summary_must_be_edited BOOLEAN,
+CHANGE prompt_owner_id owner_id INT,
+CHANGE prompt_status status VARCHAR(255),
+CHANGE prompt_members_only members_only BOOLEAN;
+
+
+================================================================
+2013-11-18: add LocalIDCounter to primary DB only, and fill in values.
+
+CREATE TABLE LocalIDCounter (
+  project_id SMALLINT UNSIGNED NOT NULL,
+  used_local_id INT NOT NULL,
+
+  PRIMARY KEY (project_id),
+  FOREIGN KEY (project_id) REFERENCES Project(project_id)
+) ENGINE=INNODB;
+
+
+-- Note: this ignores former issue locations, so it can only be run
+-- now, before the "move issue" feature is offered.
+REPLACE INTO LocalIDCounter
+SELECT project_id, MAX(local_id)
+FROM Issue
+GROUP BY project_id;
+
+================================================================
+2015-06-12: add issue_id to Invalidate's enum for kind.
+
+ALTER TABLE Invalidate CHANGE kind kind ENUM('user', 'project', 'issue', 'issue_id');
+
+================================================================
+2015-07-24: Rename blobkey to gcs_object_id because we are using
+Google Cloud storage now.
+
+ALTER TABLE Attachment CHANGE blobkey gcs_object_id VARCHAR(1024) NOT NULL;
+
+===============================================================
+2015-08-14: Use MurmurHash3 to deterministically generate user ids.
+
+-- First, drop foreign key constraints, then alter the keys, then
+-- add back the foreign key constraints.
+
+ALTER TABLE User2Project DROP FOREIGN KEY user2project_ibfk_2;
+ALTER TABLE ExtraPerm DROP FOREIGN KEY extraperm_ibfk_2;
+ALTER TABLE MemberNotes DROP FOREIGN KEY membernotes_ibfk_2;
+ALTER TABLE UserStar DROP FOREIGN KEY userstar_ibfk_1;
+ALTER TABLE UserStar DROP FOREIGN KEY userstar_ibfk_2;
+ALTER TABLE ProjectStar DROP FOREIGN KEY projectstar_ibfk_1;
+ALTER TABLE UserGroup DROP FOREIGN KEY usergroup_ibfk_1;
+ALTER TABLE UserGroup DROP FOREIGN KEY usergroup_ibfk_2;
+ALTER TABLE UserGroupSettings DROP FOREIGN KEY usergroupsettings_ibfk_1;
+ALTER TABLE QuickEditHistory DROP FOREIGN KEY quickedithistory_ibfk_2;
+ALTER TABLE QuickEditMostRecent DROP FOREIGN KEY quickeditmostrecent_ibfk_2;
+ALTER TABLE Issue DROP FOREIGN KEY issue_ibfk_2;
+ALTER TABLE Issue DROP FOREIGN KEY issue_ibfk_3;
+ALTER TABLE Issue DROP FOREIGN KEY issue_ibfk_4;
+ALTER TABLE Issue2Cc DROP FOREIGN KEY issue2cc_ibfk_2;
+ALTER TABLE IssueStar DROP FOREIGN KEY issuestar_ibfk_1;  -- ?
+ALTER TABLE Issue2FieldValue DROP FOREIGN KEY issue2fieldvalue_ibfk_2;
+ALTER TABLE Comment DROP FOREIGN KEY comment_ibfk_3;
+ALTER TABLE Comment DROP FOREIGN KEY comment_ibfk_4;
+ALTER TABLE FieldDef2Admin DROP FOREIGN KEY fielddef2admin_ibfk_2;
+ALTER TABLE Template2Admin DROP FOREIGN KEY template2admin_ibfk_2;
+ALTER TABLE Template2FieldValue DROP FOREIGN KEY template2fieldvalue_ibfk_2;
+ALTER TABLE Component2Admin DROP FOREIGN KEY component2admin_ibfk_2;
+ALTER TABLE Component2Cc DROP FOREIGN KEY component2cc_ibfk_2;
+ALTER TABLE User2SavedQuery DROP FOREIGN KEY user2savedquery_ibfk_1;
+
+
+ALTER TABLE User MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE ActionLimit MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE DismissedCues MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE User2Project MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE ExtraPerm MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE MemberNotes MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE UserStar MODIFY starred_user_id INT UNSIGNED NOT NULL,
+                     MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE ProjectStar MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE UserGroup MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE UserGroup MODIFY group_id INT UNSIGNED NOT NULL;
+ALTER TABLE UserGroupSettings MODIFY group_id INT UNSIGNED NOT NULL;
+ALTER TABLE QuickEditHistory MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE QuickEditMostRecent MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE Issue MODIFY reporter_id INT UNSIGNED NOT NULL,
+                  MODIFY owner_id INT UNSIGNED,
+                  MODIFY derived_owner_id INT UNSIGNED;
+ALTER TABLE Issue2Cc MODIFY cc_id INT UNSIGNED NOT NULL;
+ALTER TABLE IssueStar MODIFY user_id INT UNSIGNED NOT NULL;
+ALTER TABLE Issue2FieldValue MODIFY user_id INT UNSIGNED;
+ALTER TABLE Comment MODIFY commenter_id INT UNSIGNED NOT NULL;
+ALTER TABLE Comment MODIFY deleted_by INT UNSIGNED;
+ALTER TABLE IssueUpdate MODIFY added_user_id INT UNSIGNED,
+                        MODIFY removed_user_id INT UNSIGNED;
+ALTER TABLE Template MODIFY owner_id INT UNSIGNED;
+ALTER TABLE FieldDef2Admin MODIFY admin_id INT UNSIGNED NOT NULL;
+ALTER TABLE Template2Admin MODIFY admin_id INT UNSIGNED NOT NULL;
+ALTER TABLE Template2FieldValue MODIFY user_id INT UNSIGNED;
+ALTER TABLE Component2Admin MODIFY admin_id INT UNSIGNED NOT NULL;
+ALTER TABLE Component2Cc MODIFY cc_id INT UNSIGNED NOT NULL;
+ALTER TABLE User2SavedQuery MODIFY user_id INT UNSIGNED NOT NULL;
+
+ALTER TABLE User2Project ADD CONSTRAINT user2project_ibfk_2 FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE ExtraPerm ADD CONSTRAINT extraperm_ibfk_2  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE MemberNotes ADD CONSTRAINT membernotes_ibfk_2  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE UserStar ADD CONSTRAINT userstar_ibfk_1  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE UserStar ADD CONSTRAINT userstar_ibfk_2  FOREIGN KEY (starred_user_id) REFERENCES User(user_id);
+ALTER TABLE ProjectStar ADD CONSTRAINT projectstar_ibfk_1  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE UserGroup ADD CONSTRAINT usergroup_ibfk_1  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE UserGroup ADD CONSTRAINT usergroup_ibfk_2  FOREIGN KEY (group_id) REFERENCES User(user_id);
+ALTER TABLE UserGroupSettings ADD CONSTRAINT usergroupsettings_ibfk_1  FOREIGN KEY (group_id) REFERENCES User(user_id);
+ALTER TABLE QuickEditHistory ADD CONSTRAINT quickedithistory_ibfk_2  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE QuickEditMostRecent ADD CONSTRAINT quickeditmostrecent_ibfk_2  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE Issue ADD CONSTRAINT issue_ibfk_2  FOREIGN KEY (reporter_id) REFERENCES User(user_id);
+ALTER TABLE Issue ADD CONSTRAINT issue_ibfk_3  FOREIGN KEY (owner_id) REFERENCES User(user_id);
+ALTER TABLE Issue ADD CONSTRAINT issue_ibfk_4  FOREIGN KEY (derived_owner_id) REFERENCES User(user_id);
+ALTER TABLE Issue2Cc ADD CONSTRAINT issue2cc_ibfk_2  FOREIGN KEY (cc_id) REFERENCES User(user_id);
+ALTER TABLE IssueStar ADD CONSTRAINT issuestar_ibfk_1  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE Issue2FieldValue ADD CONSTRAINT issue2fieldvalue_ibfk_2  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE Comment ADD CONSTRAINT comment_ibfk_3  FOREIGN KEY (commenter_id) REFERENCES User(user_id);
+ALTER TABLE Comment ADD CONSTRAINT comment_ibfk_4  FOREIGN KEY (deleted_by) REFERENCES User(user_id);
+ALTER TABLE FieldDef2Admin ADD CONSTRAINT fielddef2admin_ibfk_2  FOREIGN KEY (admin_id) REFERENCES User(user_id);
+ALTER TABLE Template2Admin ADD CONSTRAINT template2admin_ibfk_2  FOREIGN KEY (admin_id) REFERENCES User(user_id);
+ALTER TABLE Template2FieldValue ADD CONSTRAINT template2fieldvalue_ibfk_2  FOREIGN KEY (user_id) REFERENCES User(user_id);
+ALTER TABLE Component2Admin ADD CONSTRAINT component2admin_ibfk_2  FOREIGN KEY (admin_id) REFERENCES User(user_id);
+ALTER TABLE Component2Cc ADD CONSTRAINT component2cc_ibfk_2  FOREIGN KEY (cc_id) REFERENCES User(user_id);
+ALTER TABLE User2SavedQuery ADD CONSTRAINT user2savedquery_ibfk_1  FOREIGN KEY (user_id) REFERENCES User(user_id);
+
+================================================================
+2015-08-20: Add obscure_email column to User.
+
+ALTER TABLE User ADD obscure_email BOOLEAN DEFAULT TRUE;
+
+================================================================
+2015-09-14: Add role column to UserGroup.
+
+ALTER TABLE UserGroup ADD COLUMN role ENUM ('owner', 'member') NOT NULL DEFAULT 'member';
+
+================================================================
+2015-09-14: Remove via_id column from UserGroup.
+
+ALTER TABLE UserGroup DROP COLUMN via_id;
+
+================================================================
+2015-09-14: Add foreign key constraints to Issue2Foo tables
+
+ALTER TABLE Issue ADD CONSTRAINT issue_ibfk_5  FOREIGN KEY (status_id) REFERENCES StatusDef(id);
+ALTER TABLE Issue2Component ADD CONSTRAINT issue2component_ibfk_2  FOREIGN KEY (component_id) REFERENCES ComponentDef(id);
+ALTER TABLE Issue2Label ADD CONSTRAINT issue2label_ibfk_2  FOREIGN KEY (label_id) REFERENCES LabelDef(id);
+ALTER TABLE Issue2FieldValue ADD CONSTRAINT issue2fieldvalue_ibfk_3  FOREIGN KEY (field_id) REFERENCES FieldDef(id);
+
+================================================================
+2015-09-16: Use Binary collation on Varchar unique keys
+
+ALTER TABLE StatusDef MODIFY status VARCHAR(80) BINARY NOT NULL;
+ALTER TABLE ComponentDef MODIFY path VARCHAR(255) BINARY NOT NULL;
+ALTER TABLE LabelDef MODIFY label VARCHAR(80) BINARY NOT NULL;
+ALTER TABLE FieldDef MODIFY field_name VARCHAR(80) BINARY NOT NULL;
+ALTER TABLE Template MODIFY name VARCHAR(255) BINARY NOT NULL;
+
+================================================================
+2015-09-16: Have components use the same ID schema as Labels/Statuses
+
+ALTER TABLE ComponentDef MODIFY id INT NOT NULL AUTO_INCREMENT;
+ALTER TABLE Component2Admin MODIFY component_id INT NOT NULL;
+ALTER TABLE Component2Cc MODIFY component_id INT NOT NULL;
+ALTER TABLE Issue2Component MODIFY component_id INT NOT NULL;
+
+================================================================
+2015-09-17: Introduce DanglingIssueRelation table
+
+ALTER TABLE IssueRelation ADD CONSTRAINT issuerelation_ibfk_2  FOREIGN KEY (dst_issue_id) REFERENCES Issue(id);
+
+CREATE TABLE DanglingIssueRelation (
+  issue_id INT NOT NULL,
+  dst_issue_project VARCHAR(80),
+  dst_issue_local_id INT,
+
+  -- This table uses 'blocking' so that it can guarantee the src issue
+  -- always exists, while the dst issue is always the dangling one.
+  kind ENUM ('blockedon', 'blocking', 'mergedinto') NOT NULL,
+
+  PRIMARY KEY (issue_id, dst_issue_project, dst_issue_local_id),
+  INDEX (issue_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id)
+) ENGINE=INNODB;
+
+================================================================
+2015-09-18: Convert table char encodings to utf8.
+
+ALTER DATABASE monorail CHARACTER SET = utf8 COLLATE = utf8_unicode_ci;
+ALTER TABLE Comment CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE ComponentDef CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE FieldDef CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE IssueSummary CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE LabelDef CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE MemberNotes CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE Project CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+ALTER TABLE StatusDef CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
+
+================================================================
+2015-09-22: Make IssueRelation primary key more specific
+
+ALTER TABLE IssueRelation DROP PRIMARY KEY, ADD PRIMARY KEY (issue_id, dst_issue_id, kind);
+ALTER TABLE DanglingIssueRelation DROP PRIMARY KEY, ADD PRIMARY KEY (issue_id, dst_issue_project, dst_issue_local_id, kind);
+
+================================================================
+2015-09-29: Make cache_key unsigned so unsigned user ids can be invalidated.
+
+ALTER TABLE Invalidate MODIFY cache_key INT UNSIGNED NOT NULL;
+
+================================================================
+2015-09-29: Add external_group_type and external_group_name to UserGroupSettings
+
+ALTER TABLE UserGroupSettings ADD COLUMN external_group_type ENUM ('chrome_infra_auth', 'mdb');
+ALTER TABLE UserGroupSettings ADD COLUMN last_sync_time INT;
+
+================================================================
+2015-10-27: Eliminate Project.deliver_outbound_email because we have separate staging and prod instances.
+
+ALTER TABLE Project DROP COLUMN deliver_outbound_email;
+
+================================================================
+2015-10-27: Add SpamReport and is_spam fields to Issue and Comment
+
+ALTER TABLE Issue ADD COLUMN is_spam BOOL DEFAULT FALSE;
+ALTER TABLE Issue ADD INDEX (is_spam, project_id);
+
+ALTER TABLE Comment ADD COLUMN is_spam BOOL DEFAULT FALSE;
+ALTER TABLE Comment ADD INDEX (is_spam, project_id, created);
+
+-- Created whenever a user reports an issue or comment as spam.
+-- Note this is distinct from a SpamVerdict, which is issued by
+-- the system rather than a human user.
+CREATE TABLE SpamReport (
+  -- when this report was generated
+  created TIMESTAMP NOT NULL,
+  -- when the reported content was generated
+  content_created TIMESTAMP NOT NULL,
+	-- id of the reporting user
+  user_id INT UNSIGNED NOT NULL,
+	-- id of the reported user
+  reported_user_id INT UNSIGNED NOT NULL,
+  -- either this or issue_id must be set
+  comment_id INT,
+  -- either this or comment_id must be set
+  issue_id INT,
+
+  INDEX (issue_id),
+  INDEX (comment_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id),
+  FOREIGN KEY (comment_id) REFERENCES Comment(id)
+);
+
+================================================================
+2015-11-03: Add new external group type chromium_committers
+
+ALTER TABLE UserGroupSettings MODIFY COLUMN external_group_type ENUM ('chrome_infra_auth', 'mdb', 'chromium_committers');
+
+================================================================
+2015-11-4: Add SpamVerdict table.
+
+-- Any time a human or the system sets is_spam to true,
+-- or changes it from true to false, we want to have a
+-- record of who did it and why.
+CREATE TABLE SpamVerdict (
+  -- when this verdict was generated
+  created TIMESTAMP NOT NULL,
+
+	-- id of the reporting user, may be null if it was
+  -- an automatic classification.
+  user_id INT UNSIGNED,
+
+  -- either this or issue_id must be set
+  comment_id INT,
+
+  -- either this or comment_id must be set
+  issue_id INT,
+
+  INDEX (issue_id),
+  INDEX (comment_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id),
+  FOREIGN KEY (comment_id) REFERENCES Comment(id),
+
+  -- If the classifier issued the verdict, this should
+  -- be set.
+  classifier_confidence FLOAT,
+
+  -- This should reflect the new is_spam value that was applied
+  -- by this verdict, not the value it had prior.
+  is_spam BOOLEAN NOT NULL,
+
+  -- owner: a project owner marked it as spam
+  -- threshhold: number of SpamReports from non-members was exceeded.
+  -- classifier: the automatic classifier reports it as spam.
+  reason ENUM ("manual", "threshold", "classifier") NOT NULL
+);
+
+ALTER TABLE LocalIDCounter ADD used_spam_id int(11) NOT NULL;
+
+================================================================
+2015-11-13: Add Template2Component table.
+
+CREATE TABLE Template2Component (
+  template_id INT NOT NULL,
+  component_id INT NOT NULL,
+
+  PRIMARY KEY (template_id, component_id),
+
+  FOREIGN KEY (template_id) REFERENCES Template(id),
+  FOREIGN KEY (component_id) REFERENCES ComponentDef(id)
+) ENGINE=INNODB;
+
+================================================================
+2015-11-13: Add new external group type baggins
+
+ALTER TABLE UserGroupSettings MODIFY COLUMN external_group_type ENUM ('chrome_infra_auth', 'mdb', 'chromium_committers', 'baggins');
+
+================================================================
+2015-11-18: Add new action kind api_request in ActionLimit
+
+ALTER TABLE ActionLimit MODIFY COLUMN action_kind ENUM ('project_creation', 'issue_comment', 'issue_attachment', 'issue_bulk_edit', 'api_request');
+
+================================================================
+2015-11-24: Add shard column to Issue, add indexes, and UPDATE existing rows.
+
+ALTER TABLE Issue ADD COLUMN shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL;
+
+UPDATE Issue set shard = id % 10;
+
+ALTER TABLE Issue ADD INDEX (shard, status_id);
+ALTER TABLE Issue ADD INDEX (shard, project_id);
+
+================================================================
+2015-11-25: Remove external group type chromium_committers
+
+ALTER TABLE UserGroupSettings MODIFY COLUMN external_group_type ENUM ('chrome_infra_auth', 'mdb', 'baggins');
+
+================================================================
+2015-12-08: Modify handling of hidden well-known labels/statuses
+
+ALTER TABLE StatusDef ADD COLUMN hidden BOOLEAN DEFAULT FALSE;
+ALTER TABLE LabelDef ADD COLUMN hidden BOOLEAN DEFAULT FALSE;
+
+UPDATE StatusDef SET status=TRIM(LEADING '#' FROM status), hidden=TRUE WHERE status COLLATE UTF8_GENERAL_CI LIKE '#%';
+UPDATE LabelDef SET label=TRIM(LEADING '#' FROM label), hidden=TRUE WHERE label COLLATE UTF8_GENERAL_CI LIKE '#%';
+
+================================================================
+2015-12-11: Speed up moderation queue queries.
+
+ALTER TABLE SpamVerdict ADD INDEX(classifier_confidence);
+
+================================================================
+2015-12-14: Give components 'deprecated' col to match labels/statuses
+
+ALTER TABLE StatusDef CHANGE hidden deprecated BOOLEAN DEFAULT FALSE;
+ALTER TABLE LabelDef CHANGE hidden deprecated BOOLEAN DEFAULT FALSE;
+ALTER TABLE ComponentDef ADD COLUMN deprecated BOOLEAN DEFAULT FALSE;
+
+================================================================
+2015-12-14: Add table Group2Project
+
+CREATE TABLE Group2Project (
+  group_id INT UNSIGNED NOT NULL,
+  project_id SMALLINT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (group_id, project_id),
+
+  FOREIGN KEY (group_id) REFERENCES UserGroupSettings(group_id),
+  FOREIGN KEY (project_id) REFERENCES Project(project_id)
+) ENGINE=INNODB;
+
+================================================================
+2015-12-15: Increase maximum attachment quota bytes
+
+ALTER TABLE Project MODIFY attachment_bytes_used BIGINT DEFAULT 0;
+ALTER TABLE Project MODIFY attachment_quota BIGINT DEFAULT 0;
+
+================================================================
+2015-12-15: Simplify moderation queue queries.
+
+ALTER TABLE SpamVerdict ADD COLUMN overruled BOOL NOT NULL;
+ALTER TABLE SpamVerdict ADD COLUMN project_id INT NOT NULL;
+UPDATE SpamVerdict s JOIN Issue i ON i.id=s.issue_id SET s.project_id=i.project_id;
+
+================================================================
+2015-12-17: Add cols home_page and logo to table Project
+
+ALTER TABLE Project ADD COLUMN home_page VARCHAR(250);
+ALTER TABLE Project ADD COLUMN logo_gcs_id VARCHAR(250);
+ALTER TABLE Project ADD COLUMN logo_file_name VARCHAR(250);
+
+================================================================
+2015-12-28: Add component_required col to table Template;
+
+ALTER TABLE Template ADD component_required BOOLEAN DEFAULT FALSE;
+
+================================================================
+2016-01-05: Add issue_shard column to Issue2Label, Issue2Component,
+add indexes, and UPDATE existing rows.
+
+ALTER TABLE Issue2Component ADD COLUMN issue_shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL;
+UPDATE Issue2Component set issue_shard = issue_id % 10;
+ALTER TABLE Issue2Component ADD INDEX (component_id, issue_shard);
+
+ALTER TABLE Issue2Label ADD COLUMN issue_shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL;
+UPDATE Issue2Label set issue_shard = issue_id % 10;
+ALTER TABLE Issue2Label ADD INDEX (label_id, issue_shard);
+
+================================================================
+2016-01-06: Add period_soft_limit and period_hard_limit columns to ActionLimit
+
+ALTER TABLE ActionLimit ADD COLUMN period_soft_limit INT;
+ALTER TABLE ActionLimit ADD COLUMN period_hard_limit INT;
+
+================================================================
+2016-01-08: Add issue_shard column to Issue2FieldValue, Issue2Cc,
+add indexes, and UPDATE existing rows.
+
+ALTER TABLE Issue2FieldValue ADD COLUMN issue_shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL;
+UPDATE Issue2FieldValue SET issue_shard = issue_id % 10;
+ALTER TABLE Issue2FieldValue ADD INDEX (field_id, issue_shard, int_value);
+ALTER TABLE Issue2FieldValue ADD INDEX (field_id, issue_shard, str_value(255));
+ALTER TABLE Issue2FieldValue ADD INDEX (field_id, issue_shard, user_id);
+
+ALTER TABLE Issue2Cc ADD COLUMN issue_shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL;
+UPDATE Issue2Cc SET issue_shard = issue_id % 10;
+ALTER TABLE Issue2Cc ADD INDEX (cc_id, issue_shard);
+
+================================================================
+2015-12-17: Add documentation forwarding for /wiki urls
+
+ALTER TABLE Project ADD COLUMN docs_url VARCHAR(250);
+
+================================================================
+2015-12-17: Ensure SavedQueries never have null ids
+
+ALTER TABLE SavedQuery MODIFY id INT NOT NULL AUTO INCREMENT;
+
+================================================================
+2016-02-04: Add created, creator_id, modified, modifier_id for components
+
+ALTER TABLE ComponentDef ADD COLUMN created INT;
+ALTER TABLE ComponentDef ADD COLUMN creator_id INT UNSIGNED;
+ALTER TABLE ComponentDef ADD FOREIGN KEY (creator_id) REFERENCES User(user_id);
+ALTER TABLE ComponentDef ADD COLUMN modified INT;
+ALTER TABLE ComponentDef ADD COLUMN modifier_id INT UNSIGNED;
+ALTER TABLE ComponentDef ADD FOREIGN KEY (modifier_id) REFERENCES User(user_id);
+
+================================================================
+2016-02-19: Opt all privileged accounts into displaying full email.
+
+UPDATE User SET obscure_email = FALSE WHERE email LIKE "%@chromium.org";
+UPDATE User SET obscure_email = FALSE WHERE email LIKE "%@webrtc.org";
+UPDATE User SET obscure_email = FALSE WHERE email LIKE "%@google.com";
+
+================================================================
+2016-04-11: Increase email length limit to 255
+
+ALTER TABLE User MODIFY email VARCHAR(255);
+
+================================================================
+2016-04-14: Add forwarding for /source urls
+
+ALTER TABLE Project ADD COLUMN source_url VARCHAR(250);
+
+================================================================
+2016-04-27: Add prefs for compact email subject lines
+
+ALTER TABLE User ADD COLUMN email_compact_subject BOOLEAN DEFAULT FALSE;
+ALTER TABLE User ADD COLUMN email_view_widget BOOLEAN DEFAULT TRUE;
+
+================================================================
+2016-05-13: Add component labels
+
+CREATE TABLE Component2Label (
+  component_id INT NOT NULL,
+  label_id INT NOT NULL,
+
+  PRIMARY KEY (component_id, label_id),
+
+  FOREIGN KEY (component_id) REFERENCES ComponentDef(id),
+  FOREIGN KEY (label_id) REFERENCES LabelDef(id)
+) ENGINE=INNODB;
+
+================================================================
+2016-05-23: Add default search for members
+
+ALTER TABLE ProjectIssueConfig ADD COLUMN member_default_query TEXT;
+
+================================================================
+2016-06-17: Add is_description column to Comment
+
+Local:
+% pt-online-schema-change --alter "ADD COLUMN is_description BOOLEAN DEFAULT FALSE" D=monorail,t=Comment --host=localhost --user=root --alter-foreign-keys-method=rebuild_constraints --execute
+
+Staging/Production:
+% pt-online-schema-change --alter "ADD COLUMN is_description BOOLEAN DEFAULT FALSE" D=monorail,t=Comment,h=<primary IP address>,u=$USER,p=test --alter-forieign-keys-method=rebuild_constraints --recursion-method=hosts --execute
+
+================================================================
+2016-05-13: Add table AutocompleteExclusion
+
+CREATE TABLE AutocompleteExclusion (
+  project_id SMALLINT UNSIGNED NOT NULL,
+  user_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (project_id, user_id),
+  FOREIGN KEY (project_id) REFERENCES Project(project_id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+===============================================================
+2016-06-30: Update table character encodings to allow Emoji support.
+
+/* DO NOT RUN THESE STATEMENTS ON PROD OR STAGING. They are fine for localhost
+but be warned they will lock the db for some time if you have gigs of data in
+these tables */
+
+ALTER TABLE `monorail`.`Comment` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+ALTER TABLE `monorail`.`IssueUpdate` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+ALTER TABLE `monorail`.`IssueSummary` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+
+/* This is what I ran on production: */
+% pt-online-schema-change --alter "CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci" D=monorail,t=Comment,h=<primary IP> --alter-foreign-keys-method=rebuild_constraints --no-drop-old-table --recursion-method=hosts --check-slave-lag=h=<one of the replicas' IP> --print --execute
+
+% pt-online-schema-change --alter "CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci" D=monorail,t=IssueUpdate,h=<primary IP> --alter-foreign-keys-method=rebuild_constraints --no-drop-old-table --recursion-method=hosts --check-slave-lag=h=<one of the replicas' IP> --print --execute
+
+% pt-online-schema-change --alter "CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci" D=monorail,t=IssueSummary,h=<primary IP> --alter-foreign-keys-method=rebuild_constraints --no-drop-old-table --recursion-method=hosts --check-slave-lag=h=<one of the replicas' IP> --print --execute
+
+/* And then these two which ran very quickly: */
+ALTER TABLE `monorail`.`Template` CHANGE `content` `content` text CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+ALTER TABLE `monorail`.`Template` CHANGE `summary` `summary` text CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+
+===============================================================
+2016-07-07: Add rank to IssueRelation
+
+ALTER TABLE IssueRelation ADD COLUMN rank BIGINT;
+
+==============================================================
+2016-07-13: Set default rank for blockedon relations
+
+UPDATE IssueRelation SET rank = 0 WHERE kind = 'blockedon';
+
+================================================================
+2016-08-01: Add timestamps for issue field changes
+
+DO NOT RUN THIS STATEMENT ON PROD OR STAGING.  It is fine for localhost
+but be warned that it will lock the db for some time if you have gigs of data in
+these tables.
+ALTER TABLE Issue
+  ADD COLUMN owner_modified INT,
+  ADD COLUMN status_modified INT,
+  ADD COLUMN component_modified INT;
+
+Staging/Production:
+% pt-online-schema-change \
+  --alter "ADD COLUMN owner_modified INT, ADD COLUMN status_modified INT, ADD COLUMN component_modified INT" \
+  D=monorail,t=Issue,h=<primary IP address>,u=$USER,p=<your mysql password> \
+  --alter-foreign-keys-method=rebuild_constraints --recursion-method=hosts --execute
+
+==============================================================
+2016-08-05: Add tables Hotlist, Hotlist2Issue, Hotlist2User
+
+CREATE TABLE Hotlist (
+  id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+  name VARCHAR(80) NOT NULL,
+
+  summary TEXT,
+  description TEXT,
+
+  is_private BOOLEAN DEFAULT FALSE,
+
+  PRIMARY KEY (id)
+) ENGINE=INNODB;
+
+
+CREATE TABLE Hotlist2Issue (
+  hotlist_id INT UNSIGNED NOT NULL,
+  issue_id INT NOT NULL,
+
+  rank BIGINT NOT NULL,
+
+  PRIMARY KEY (hotlist_id, issue_id),
+  INDEX (hotlist_id),
+  INDEX (issue_id),
+  FOREIGN KEY (hotlist_id) REFERENCES Hotlist(id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id)
+) ENGINE=INNODB;
+
+
+CREATE TABLE Hotlist2User (
+  hotlist_id INT UNSIGNED NOT NULL,
+  user_id INT UNSIGNED NOT NULL,
+
+  role_name ENUM ('owner', 'member', 'follower') NOT NULL,
+
+  PRIMARY KEY (hotlist_id, user_id),
+  INDEX (hotlist_id),
+  INDEX (user_id),
+  FOREIGN KEY (hotlist_id) REFERENCES Hotlist(id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+==============================================================
+2016-08-10: Improve Hotlist schema
+
+ALTER TABLE Hotlist ADD COLUMN default_col_spec TEXT;
+
+ALTER TABLE Hotlist2User CHANGE role_name
+  role_name ENUM('owner', 'editor', 'follower');
+
+==============================================================
+2016-08-15: Add hotlist to Invalidate table
+
+ALTER TABLE Invalidate CHANGE kind
+  kind ENUM('user', 'project', 'issue', 'issue_id', 'hotlist');
+
+================================================================
+2016-09-21: Create the CommentContent table with emoji support.
+
+CREATE TABLE CommentContent (
+  id INT NOT NULL AUTO_INCREMENT,
+  -- TODO(jrobbins): drop comment_id after Comment.commentcontent_id is added.
+  comment_id INT NOT NULL,  -- Note: no forign key reference.
+  content MEDIUMTEXT COLLATE utf8mb4_unicode_ci,
+  inbound_message MEDIUMTEXT COLLATE utf8mb4_unicode_ci,
+
+  PRIMARY KEY (id),
+  UNIQUE KEY (comment_id)  -- TODO: drop this too.
+) ENGINE=INNODB CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+To copy comment strings from Comment to CommentContent, use
+the SQL procedure in monorail/tools/copy-comment-to-commentcontent.sql.
+
+If you need to roll back, you can reverse the process by reading
+and carefully using the SQL procedure in
+monorail/tools/copy-new-commentcontent-back-to-comment.sql.
+
+Optionally, after you have all comment content strings in
+CommentContent, you can reduce the size of the Comment table by using
+the procedure in monorail/tools/null-comment-table-strings.sql.
+This can make it faster to make more changes to the Comment table.
+
+================================================================
+2016-09-29: Drop was_escaped after Comment table is made smaller
+
+ALTER TABLE Comment DROP COLUMN was_escaped;
+
+================================================================
+2016-10-03: Add date-type custom fields
+
+ALTER TABLE Issue2FieldValue ADD date_value INT;
+ALTER TABLE Issue2FieldValue ADD INDEX (field_id, issue_shard, date_value);
+ALTER TABLE Template2FieldValue ADD date_value INT;
+ALTER TABLE FieldDef CHANGE field_type field_type ENUM (
+    'enum_type', 'int_type', 'str_type', 'user_type', 'date_type') NOT NULL;
+
+================================================================
+2016-10-13: Follow-up on splitting the Comment table
+
+ALTER TABLE Comment
+    DROP COLUMN content,
+    DROP COLUMN inbound_message,
+    ADD COLUMN commentcontent_id INT;
+
+ALTER TABLE Comment
+     ADD FOREIGN KEY (commentcontent_id) REFERENCES CommentContent(id);
+
+After making those schema changes, run the commands in
+tools/backfill-commentcontent-id.sql to fill in commentcontent_id
+for existing comments.
+
+================================================================
+2016-10-13: Add new User fields
+
+ALTER TABLE User
+    ADD COLUMN last_visit_timestamp INT,
+    ADD COLUMN email_bounce_timestamp INT,
+    ADD COLUMN vacation_message VARCHAR(80);
+
+================================================================
+2016-11-30: Drop unique key constraint on CommentContent.comment_id.
+This is a prerequiste for deleting the code that sets a value for
+that column.  This resolves one TODO from 2016-09-21.  Later the
+column itself can be dropped, which is the other TODO from 2016-09-21.
+
+ALTER TABLE CommentContent DROP INDEX comment_id;
+
+================================================================
+2016-12-20: Add a table to keep track of hotlists that users have
+starred.
+
+CREATE TABLE HotlistStar (
+  hotlist_id INT UNSIGNED NOT NULL,
+  user_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (hotlist_id, user_id),
+  INDEX (user_id),
+  FOREIGN KEY (hotlist_id) REFERENCES Hotlist(id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+================================================================
+2017-12-04: Add two new columns to Hotlist2Issue.
+
+ALTER TABLE Hotlist2Issue
+      ADD COLUMN adder_id INT UNSIGNED,
+      ADD COLUMN added INT,
+      ADD FOREIGN KEY (adder_id) REFERENCES User(user_id);
+
+================================================================
+2017-01-30: Add one new column to SpamVerdict.
+
+ALTER TABLE SpamVerdict CHANGE reason
+  reason ENUM ("manual", "threshold", "classifier", "fail_open") NOT NULL;
+
+================================================================
+2017-02-1: Add two tables to keep track of hotlists and bugs
+that users have visited
+
+CREATE TABLE HotlistVisitHistory (
+  hotlist_id INT UNSIGNED NOT NULL,
+  user_id INT UNSIGNED NOT NULL,
+  viewed INT NOT NULL,
+
+  PRIMARY KEY (user_id, hotlist_id),
+  FOREIGN KEY (hotlist_id) REFERENCES Hotlist(id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+CREATE TABLE IssueVisitHistory (
+  issue_id INT NOT NULL,
+  user_id INT UNSIGNED NOT NULL,
+  viewed INT NOT NULL,
+
+  PRIMARY KEY (user_id, issue_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id),
+  FOREIGN KEY (user_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+================================================================
+2017-02-16: Add 'note' column to Hotlist2Issue table.
+
+ALTER TABLE Hotlist2Issue ADD COLUMN note TEXT;
+
+
+================================================================
+2017-02-23: Add 'is_niche' column to FieldDef table.
+
+ALTER TABLE FieldDef ADD COLUMN is_niche BOOLEAN;
+
+
+================================================================
+2017-03-05: Add 'ping_who' column to FieldDef table.
+
+ALTER TABLE FieldDef
+  ADD COLUMN date_action ENUM ('no_action', 'ping_owner_only', 'ping_participants');
+
+
+================================================================
+2017-05-02: Add index to make commentby: query term faster.
+
+ALTER TABLE Comment ADD INDEX (commenter_id, deleted_by, issue_id);
+
+
+================================================================
+2017-05-12: Add user preference to ping issue starrers.
+
+ALTER TABLE User ADD COLUMN notify_starred_ping BOOLEAN DEFAULT FALSE;
+
+================================================================
+2017-06-15: Add table to map @google.com to @chromium.org accounts.
+
+CREATE TABLE LinkedAccount (
+  parent_email VARCHAR(255) NOT NULL,  -- lowercase
+  child_email VARCHAR(255) NOT NULL,  -- lowercase
+
+  KEY (parent_email),
+  UNIQUE KEY (child_email)
+) ENGINE=INNODB;
+
+================================================================
+2017-11-14: Add field_type ENUM url_type to FieldDef.
+
+ALTER TABLE FieldDef MODIFY field_type ENUM (
+  'enum_type', 'int_type', 'str_type', 'user_type', 'date_type', 'url_type') NOT NULL;
+
+ALTER TABLE Issue2FieldValue ADD COLUMN url_value VARCHAR(1024);
+ALTER TABLE Issue2FieldValue ADD INDEX (field_id, url_value);
+
+================================================================
+2017-11-22: Add url_value column to Template2FieldValue table.
+
+ALTER TABLE Template2FieldValue ADD COLUMN url_value VARCHAR(1024);
+
+================================================================
+2018-01-22: Add table to keep track of the latest timestamp that issues with
+their component data were collected and uploaded to GCS.
+
+CREATE TABLE ComponentIssueClosedIndex (
+  closed_index INT NOT NULL,
+  PRIMARY KEY (closed_index)
+) ENGINE=INNODB;
+
+================================================================
+2018-01-22: Add approval tables and approval_type to FieldDef.
+
+ALTER TABLE FieldDef MODIFY field_type ENUM (
+  'enum_type', 'int_type', 'str_type', 'user_type', 'date_type', 'url_type', 'approval_type') NOT NULL;
+
+CREATE TABLE ApprovalStatusDef (
+  id INT NOT NULL AUTO_INCREMENT,
+  field_id INT NOT NULL,
+  status VARCHAR(80) BINARY NOT NULL,
+  docstring TEXT,
+
+  PRIMARY KEY (id),
+  UNIQUE KEY (field_id, status),
+  FOREIGN KEY (field_id) REFERENCES FieldDef(id)
+) ENGINE=INNODB;
+
+CREATE TABLE Issue2ApprovalValue (
+  issue_id INT NOT NULL,
+  issue_shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL,
+  field_id INT NOT NULL,
+  status_id INT NOT NULL,
+  setter_id INT UNSIGNED,
+  set_on INT,
+
+  PRIMARY KEY (issue_id, field_id),
+  INDEX (field_id, issue_shard, status_id),
+  INDEX (field_id, issue_shard, setter_id),
+  INDEX (field_id, issue_shard, set_on),
+
+  FOREIGN KEY (issue_id) REFERENCES Issue(id),
+  FOREIGN KEY (field_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (status_id) REFERENCES ApprovalStatusDef(id),
+  FOREIGN KEY (setter_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+CREATE TABLE Approval2Approvers (
+  field_id INT NOT NULL,
+  approver_id INT UNSIGNED NOT NULL,
+  issue_id INT,
+  issue_shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL,
+
+  PRIMARY KEY (issue_id, field_id, approver_id),
+  INDEX (approver_id, field_id, issue_shard),
+
+  FOREIGN KEY (field_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (approver_id) REFERENCES User(user_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id)
+) ENGINE=INNODB;
+
+================================================================
+2018-01-29: Add is_deleted column to ComponentDef table and remove
+uniqueness constraint for component names in a project.
+
+ALTER TABLE ComponentDef ADD COLUMN is_deleted BOOLEAN DEFAULT FALSE;
+ALTER TABLE ComponentDef ADD INDEX project_id2 (project_id, path);
+ALTER TABLE ComponentDef DROP INDEX project_id;
+
+================================================================
+2018-01-30: Add IssueSnapshot table and join tables
+
+CREATE TABLE IssueSnapshot (
+  id INT NOT NULL AUTO_INCREMENT,
+  issue_id INT NOT NULL,
+  shard SMALLINT UNSIGNED DEFAULT 0 NOT NULL,
+  project_id SMALLINT UNSIGNED NOT NULL,
+  local_id INT NOT NULL,
+  reporter_id INT UNSIGNED NOT NULL,
+  owner_id INT UNSIGNED,
+  status_id INT NOT NULL,
+  period_start INT NOT NULL,
+  period_end INT NOT NULL,
+  is_open BOOLEAN DEFAULT TRUE,
+
+  PRIMARY KEY (id),
+  FOREIGN KEY (project_id) REFERENCES Project(project_id),
+  FOREIGN KEY (reporter_id) REFERENCES User(user_id),
+  FOREIGN KEY (owner_id) REFERENCES User(user_id),
+  FOREIGN KEY (status_id) REFERENCES StatusDef(id),
+  INDEX (shard, project_id, period_start, period_end),
+  UNIQUE KEY (issue_id, period_start, period_end)
+) ENGINE=INNODB;
+
+CREATE TABLE IssueSnapshot2Component (
+  issuesnapshot_id INT NOT NULL,
+  component_id INT NOT NULL,
+
+  PRIMARY KEY (issuesnapshot_id, component_id),
+  FOREIGN KEY (issuesnapshot_id) REFERENCES IssueSnapshot(id),
+  FOREIGN KEY (component_id) REFERENCES ComponentDef(id)
+) ENGINE=INNODB;
+
+CREATE TABLE IssueSnapshot2Label(
+  issuesnapshot_id INT NOT NULL,
+  label_id INT NOT NULL,
+
+  PRIMARY KEY (issuesnapshot_id, label_id),
+  FOREIGN KEY (issuesnapshot_id) REFERENCES IssueSnapshot(id),
+  FOREIGN KEY (label_id) REFERENCES LabelDef(id)
+) ENGINE=INNODB;
+
+CREATE TABLE IssueSnapshot2Cc(
+  issuesnapshot_id INT NOT NULL,
+  cc_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (issuesnapshot_id, cc_id),
+  FOREIGN KEY (issuesnapshot_id) REFERENCES IssueSnapshot(id),
+  FOREIGN KEY (cc_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+===============================================================
+2018-01-29: Add approval_id column to FieldDef table
+
+ALTER TABLE FieldDef ADD COLUMN approval_id INT;
+
+===============================================================
+2018-02-08: Drop previous approval tables and add default approvers table
+
+DROP TABLE ApprovalStatusDef;
+DROP TABLE Approval2Approver;
+DROP TABLE Issue2ApprovalValue;
+
+CREATE TABLE ApprovalDef2Approver (
+  approval_id INT NOT NULL,
+  approver_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (approval_id, approver_id),
+
+  FOREIGN KEY (approval_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (approver_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+==================================================================
+2018-02-09: Add project_id column to default approvers table
+
+ALTER TABLE ApprovalDef2Approver ADD project_id SMALLINT UNSIGNED NOT NULL;
+ALTER TABLE ApprovalDef2Approver ADD CONSTRAINT ApprovalDef2Approver_ibfk_3 FOREIGN KEY (project_id) REFERENCES Project(project_id);
+
+==================================================================
+2018-02-14: Expand IssueSnapshot time columns from INT to INT UNSIGNED
+ALTER TABLE IssueSnapshot MODIFY period_start INT UNSIGNED NOT NULL;
+ALTER TABLE IssueSnapshot MODIFY period_end INT UNSIGNED NOT NULL;
+
+
+================================================================
+2018-02-22: Relax some constraints on issue snapshots
+
+ALTER TABLE IssueSnapshot MODIFY status_id int;
+ALTER TABLE IssueSnapshot DROP INDEX issue_id;
+ALTER TABLE IssueSnapshot ADD INDEX (`issue_id`,`period_start`,`period_end`);
+
+================================================================
+2018-03-12: Add launch template milestones and approval tables
+
+CREATE TABLE Template2Milestone (
+  id INT NOT NULL AUTO_INCREMENT,
+  template_id INT NOT NULL,
+  name VARCHAR(255) BINARY NOT NULL,
+  rank SMALLINT UNSIGNED,
+
+  PRIMARY KEY (id, template_id),
+  FOREIGN KEY (template_id) REFERENCES Template(id)
+) ENGINE=INNODB;
+
+CREATE TABLE Template2ApprovalValue (
+  approval_id INT NOT NULL,
+  template_id INT NOT NULL,
+  milestone_id INT NOT NULL,
+  launch_status ENUM ('NA', 'review_requested', 'started', 'need_info', 'approved', 'not_approved'),
+
+  PRIMARY KEY (approval_id, template_id, milestone_id),
+
+  FOREIGN KEY (approval_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (template_id) REFERENCES Template(id),
+  FOREIGN KEY (milestone_id) REFERENCES Template2Milestone(id)
+) ENGINE=INNODB;
+
+
+================================================================
+2018-03-13: Edit approval state enum
+
+ALTER TABLE Template2ApprovalValue CHANGE launch_status status ENUM (
+  'needs_review', 'na', 'review_requested', 'started', 'need_info', 'approved', 'not_approved');
+
+
+================================================================
+2018-03-14: Edit approval state enum *AGAIN*
+
+ALTER TABLE Template2ApprovalValue MODIFY status ENUM (
+  'needs_review', 'na', 'review_requested', 'started', 'need_info', 'approved', 'not_approved', 'not_set');
+
+
+================================================================
+2018-03-15: Add Issue Approval and Mileston tables
+
+DROP TABLE IF EXISTS Approval2Approver;
+DROP TABLE IF EXISTS Issue2ApprovalValue;
+
+CREATE TABLE Issue2Milestone (
+  id INT NOT NULL AUTO_INCREMENT,
+  issue_id INT NOT NULL,
+  name VARCHAR(255) BINARY NOT NULL,
+  rank SMALLINT UNSIGNED,
+
+  PRIMARY KEY (id, issue_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id)
+) ENGINE=INNODB;
+
+CREATE TABLE Issue2ApprovalValue (
+  issue_id INT NOT NULL,
+  approval_id INT NOT NULL,
+  milestone_id INT NOT NULL,
+  status ENUM ('needs_review', 'na', 'review_requested', 'started', 'need_info', 'approved', 'not_approved', 'not_set') DEFAULT 'not_set' NOT NULL,
+  setter_id INT UNSIGNED,
+  set_on INT,
+
+  PRIMARY KEY (issue_id, approval_id, milestone_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id),
+  FOREIGN KEY (approval_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (milestone_id) REFERENCES Issue2Milestone(id),
+  FOREIGN KEY (setter_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+CREATE TABLE IssueApproval2Approvers (
+  issue_id INT NOT NULL,
+  approval_id INT NOT NULL,
+  approver_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (issue_id, approval_id, approver_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id),
+  FOREIGN KEY (approval_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (approver_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+ALTER TABLE Template2ApprovalValue MODIFY status ENUM (
+  'needs_review', 'na', 'review_requested', 'started', 'need_info', 'approved', 'not_approved', 'not_set') DEFAULT 'not_set' NOT NULL;
+
+================================================================
+2018-03-15: Soft-delete Hotlists.
+ALTER TABLE Hotlist ADD COLUMN is_deleted BOOLEAN DEFAULT FALSE;
+
+===============================================================
+2018-03-19: Rename issue approvers table.
+
+RENAME TABLE IssueApproval2Approvers TO IssueApproval2Approver;
+
+================================================================
+2018-03-22: Add Hotlist support to IssueSnapshots.
+
+CREATE TABLE IssueSnapshot2Hotlist(
+  issuesnapshot_id INT NOT NULL,
+  hotlist_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (issuesnapshot_id, hotlist_id),
+  FOREIGN KEY (issuesnapshot_id) REFERENCES IssueSnapshot(id),
+  FOREIGN KEY (hotlist_id) REFERENCES Hotlist(id)
+) ENGINE=INNODB;
+
+================================================================
+2018-03-23: Add ApprovalDef2Survey table.
+
+CREATE TABLE ApprovalDef2Survey (
+  approval_id INT NOT NULL,
+  survey TEXT,
+  project_id SMALLINT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (approval_id, project_id),
+
+  FOREIGN KEY (approval_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (project_id) REFERENCES Project(project_id)
+) ENGINE=INNODB;
+
+===============================================================
+2018-03-24: Add IssueApproval2Comment table.
+
+CREATE TABLE IssueApproval2Comment (
+  approval_id INT NOT NULL,
+  comment_id INT NOT NULL,
+
+  PRIMARY KEY (comment_id),
+  INDEX (approval_id),
+  FOREIGN KEY (approval_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (comment_id) REFERENCES Comment(id)
+) ENGINE=INNODB;
+
+===============================================================
+2018-03-29: Rename Milestones to Phases.
+
+CREATE TABLE Issue2Phase (
+  id INT NOT NULL AUTO_INCREMENT,
+  issue_id INT NOT NULL,
+  name VARCHAR(255) BINARY NOT NULL,
+  rank SMALLINT UNSIGNED,
+
+  PRIMARY KEY (id, issue_id),
+  FOREIGN KEY (issue_id) REFERENCES Issue(id)
+) ENGINE=INNODB;
+
+CREATE TABLE Template2Phase (
+  id INT NOT NULL AUTO_INCREMENT,
+  template_id INT NOT NULL,
+  name VARCHAR(255) BINARY NOT NULL,
+  rank SMALLINT UNSIGNED,
+
+  PRIMARY KEY (id, template_id),
+  FOREIGN KEY (template_id) REFERENCES Template(id)
+) ENGINE=INNODB;
+
+ALTER TABLE Issue2ApprovalValue DROP FOREIGN KEY Issue2ApprovalValue_ibfk_4;
+ALTER TABLE Issue2ApprovalValue ADD COLUMN phase_id int NOT NULL;
+CREATE INDEX IF NOT EXISTS phase_id ON Issue2ApprovalValue (phase_id);
+ALTER TABLE Issue2ApprovalValue ADD FOREIGN KEY (phase_id) REFERENCES Issue2Phase(id);
+
+ALTER TABLE Template2ApprovalValue DROP FOREIGN KEY Template2ApprovalValue_ibfk_3;
+ALTER TABLE Template2ApprovalValue ADD COLUMN phase_id int NOT NULL;
+CREATE INDEX IF NOT EXISTS phase_id ON Template2ApprovalValue (phase_id);
+ALTER TABLE Template2ApprovalValue ADD FOREIGN KEY (phase_id) REFERENCES Template2Phase(id);
+
+================================================================
+2018-04-18: Drop all milestone schema.
+
+ALTER TABLE Template2ApprovalValue DROP COLUMN milestone_id;
+ALTER TABLE Issue2ApprovalValue DROP COLUMN milestone_id;
+
+DROP TABLE Template2Milestone;
+DROP TABLE Issue2Milestone;
+
+================================================================
+2018-04-25: Add phase_id to X2ApprovalValue tables' primary keys.
+
+ALTER TABLE Template2ApprovalValue DROP PRIMARY KEY, ADD PRIMARY KEY(approval_id, template_id, phase_id);
+ALTER TABLE Issue2ApprovalValue DROP PRIMARY KEY, ADD PRIMARY KEY(issue_id, approval_id, phase_id);
+
+==================================================================
+2018-04-30: Rename Issue2Phase table to IssuePhaseDef: Part One
+
+CREATE TABLE IssuePhaseDef (
+  id INT NOT NULL AUTO_INCREMENT,
+  name VARCHAR(255) BINARY NOT NULL,
+  rank SMALLINT UNSIGNED,
+
+  PRIMARY KEY (id)
+) ENGINE=INNODB;
+
+ALTER TABLE Issue2ApprovalValue DROP FOREIGN KEY Issue2ApprovalValue_ibfk_4;
+ALTER TABLE Issue2ApprovalValue ADD FOREIGN KEY (phase_id) REFERENCES IssuePhaseDef(id);
+
+==================================================================
+2018-05-02: Add phase_id to Issue2FieldValue table.
+
+ALTER TABLE Issue2FieldValue ADD COLUMN phase_id INT;
+ALTER TABLE Issue2FieldValue ADD FOREIGN KEY (phase_id) REFERENCES IssuePhaseDef(id);
+
+===================================================================
+2018-5-01: Add is_phase_field to FieldDef.
+
+ALTER TABLE FieldDef ADD COLUMN is_phase_field BOOLEAN DEFAULT FALSE;
+
+===================================================================
+2018-5-11: Rename Issue2Phase table to IssuePhaseDef: Part Two, drop Issue2Phase
+
+DROP TABLE Issue2Phase;
+==================================================================
+2018-05-11: Restrict size of index field in Issue2FieldValue
+
+ALTER TABLE Issue2FieldValue DROP INDEX field_id_5;
+ALTER TABLE Issue2FieldValue ADD INDEX (field_id, issue_shard, url_value(255));
+
+==================================================================
+2018-05-18: Replace Template2Phase FK with IssuePhaseDef.
+
+TRUNCATE TABLE Template2ApprovalValue;
+ALTER TABLE Template2ApprovalValue DROP FOREIGN KEY Template2ApprovalValue_ibfk_3;
+ALTER TABLE Template2ApprovalValue ADD FOREIGN KEY (phase_id) REFERENCES IssuePhaseDef(id);
+
+================================================================
+2018-05-22: Add boolean columns to control autocomplete exclusions.
+
+ALTER TABLE AutocompleteExclusion
+  ADD COLUMN ac_exclude BOOLEAN DEFAULT TRUE,
+  ADD COLUMN no_expand BOOLEAN DEFAULT FALSE;
+
+==================================================================
+2018-05-30: Add comment to Invalidate table
+
+ALTER TABLE Invalidate CHANGE kind
+  kind ENUM('user', 'project', 'issue', 'issue_id', 'hotlist',
+      'comment');
+
+=================================================================
+2018-06-05: Drop Template2Phase tbl and NOT NULL constraint for approval value phase_id columns.
+
+DROP TABLE Template2Phase;
+
+ALTER TABLE Issue2ApprovalValue DROP PRIMARY KEY, ADD PRIMARY KEY(issue_id, approval_id);
+ALTER TABLE Issue2ApprovalValue MODIFY COLUMN phase_id INT;
+
+ALTER TABLE Template2ApprovalValue DROP PRIMARY KEY, ADD PRIMARY KEY(approval_id, template_id);
+ALTER TABLE Template2ApprovalValue MODIFY COLUMN phase_id INT;
+
+=================================================================
+2018-06-22: Add 'template' to Invalidate.kind_enum
+
+ALTER TABLE Invalidate MODIFY COLUMN kind enum('user', 'project', 'issue', 'issue_id', 'hotlist', 'comment', 'template') NOT NULL;
+
+=================================================================
+2018-07-02: Add UserCommits table to keep track of commits.
+
+CREATE TABLE UserCommits (
+  commit_sha VARCHAR(40),
+  parent_sha VARCHAR(40),
+  author_id INT UNSIGNED NOT NULL,
+  commit_time INT NOT NULL,
+  commit_message TEXT,
+  commit_repo VARCHAR(255),
+
+  PRIMARY KEY (commit_sha),
+  INDEX (author_id, commit_time),
+  INDEX (commit_time)
+) ENGINE=INNODB;
+
+
+=================================================================
+2018-07-16: Drop parent_sha because it isn't needed in this table and give commit_repo a clearer name.
+
+ALTER TABLE UserCommits DROP COLUMN parent_sha;
+ALTER TABLE UserCommits CHANGE commit_repo commit_repo_url VARCHAR(255);
+
+
+================================================================
+2018-08-27: Allow computed external user groups, e.g., everyone@google.com.
+
+ALTER TABLE UserGroupSettings
+  MODIFY COLUMN
+  external_group_type ENUM ('chrome_infra_auth', 'mdb', 'baggins', 'computed');
+
+
+================================================================
+2018-09-24: Add 'usergroup to Invalidate.kind enum
+
+ALTER TABLE Invalidate MODIFY COLUMN kind enum(
+    'user', 'usergroup', 'project', 'issue', 'issue_id',
+    'hotlist', 'comment', 'template') NOT NULL;
+
+================================================================
+2018-10-30: Fix ApprovalValue status enum for 'review_started'
+
+ALTER TABLE Template2ApprovalValue MODIFY status ENUM (
+  'needs_review', 'na', 'review_requested', 'review_started', 'need_info', 'approved', 'not_approved', 'not_set') DEFAULT 'not_set' NOT NULL;
+
+ALTER TABLE Issue2ApprovalValue MODIFY status ENUM (
+  'needs_review', 'na', 'review_requested', 'review_started', 'need_info', 'approved', 'not_approved', 'not_set') DEFAULT 'not_set' NOT NULL;
+
+
+================================================================
+2018-11-02: Redo LinkedAccount table.
+
+DROP TABLE LinkedAccount;
+CREATE TABLE LinkedAccount (
+  parent_id INT UNSIGNED NOT NULL,
+  child_id INT UNSIGNED NOT NULL,
+
+  KEY (parent_id),
+  UNIQUE KEY (child_id),
+  FOREIGN KEY (parent_id) REFERENCES User(user_id),
+  FOREIGN KEY (child_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+================================================================
+2018-12-03: Create LinkedAccountInvite table.
+
+CREATE TABLE LinkedAccountInvite (
+  parent_id INT UNSIGNED NOT NULL,
+  child_id INT UNSIGNED NOT NULL,
+
+  KEY (parent_id),
+  UNIQUE KEY (child_id),
+  FOREIGN KEY (parent_id) REFERENCES User(user_id),
+  FOREIGN KEY (child_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+==================================================================================
+2018-1-15: Add notify_group and notify_members bool col to UserGroupSettings table.
+
+ALTER TABLE UserGroupSettings ADD COLUMN notify_members BOOLEAN DEFAULT TRUE;
+ALTER TABLE UserGroupSettings ADD COLUMN notify_group BOOLEAN DEFAULT FALSE;
+
+=================================================================
+2019-01-23: Add two new indexes to IssueSnapshot for performance.
+
+CREATE INDEX by_period_start ON IssueSnapshot (shard, project_id, status_id, period_start);
+CREATE INDEX by_period_end ON IssueSnapshot (shard, project_id, status_id, period_end);
+
+
+================================================================
+2019-01-25: Start a more flexible way of storing user preferences.
+
+CREATE TABLE UserPrefs (
+  user_id INT UNSIGNED NOT NULL,
+  name VARCHAR(40),
+  value VARCHAR(80),
+
+  UNIQUE KEY (user_id, name)
+) ENGINE=INNODB;
+
+================================================================
+2019-04-10: Set UserPrefs that indicate that privacy click-through was seen.
+This is part of phasing out DismissedCues.
+
+INSERT IGNORE INTO UserPrefs (user_id, name, value)
+SELECT user_id, cue, 'true'
+FROM DismissedCues;
+
+================================================================
+2019-05-13: Drop unused ActionLimit table.
+
+DROP TABLE ActionLimit;
+
+================================================================
+2019-05-24: Add ext_issue_identifier column to DanglingIssueRelation table.
+
+ALTER TABLE DanglingIssueRelation ADD COLUMN ext_issue_identifier VARCHAR(2048);
+ALTER TABLE DanglingIssueRelation ADD INDEX (ext_issue_identifier);
+
+================================================================
+2019-06-06: Allow full unicode labels.
+
+ALTER TABLE LabelDef CHANGE label label VARCHAR(80) BINARY NOT NULL COLLATE utf8mb4_unicode_ci;
+
+================================================================
+2019-06-07: Add indexes to reduce cases of using filesort
+
+ALTER TABLE HotlistVisitHistory ADD INDEX (user_id, viewed);
+ALTER TABLE ReindexQueue ADD INDEX (created);
+
+================================================================
+2019-06-13: Add ext_issue_identifier to DanglingIssueRelation PRIMARY KEY.
+
+ALTER TABLE DanglingIssueRelation MODIFY COLUMN ext_issue_identifier VARCHAR(255);
+ALTER TABLE DanglingIssueRelation DROP PRIMARY KEY, ADD PRIMARY KEY(issue_id, dst_issue_project, dst_issue_local_id, kind, ext_issue_identifier);
+
+================================================================
+2019-06-25: Add unique constraint on SpamReport.
+
+ALTER IGNORE TABLE SpamReport ADD UNIQUE (user_id, comment_id, issue_id);
+
+================================================================
+2019-07-03: Add CommentImporter table.
+
+CREATE TABLE CommentImporter (
+  comment_id INT NOT NULL,
+  importer_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (comment_id),
+  FOREIGN KEY (comment_id) REFERENCES Comment(id),
+  FOREIGN KEY (importer_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+================================================================
+2019-10-09: Drop DismissedCues because that data has been in UserPrefs since April.
+
+DROP TABLE DismissedCues;
+
+================================================================
+2019-10-24: Insert row representing deleted user.
+
+INSERT IGNORE INTO User (user_id, email) VALUES (1, '');
+
+==================================================================
+2019-11-21: Add hotlist_id to Invalidate table.
+
+ALTER TABLE Invalidate CHANGE kind
+  kind ENUM('user', 'usergroup', 'project', 'issue', 'issue_id', 'hotlist', 'comment', 'template', 'hotlist_id');
+
+
+================================================================
+2019-12-30: Set custom revision_url_format for pigweed project.
+
+UPDATE Project SET revision_url_format = 'https://pigweed-review.git.corp.google.com/q/{revnum}' WHERE project_name='pigweed';
+
+================================================================
+2020-02-19: Create table for editors of a field. Also, add column in FieldDef
+to indicate if the editors of that field are being restricted.
+
+CREATE TABLE FieldDef2Editor (
+  field_id INT NOT NULL,
+  editor_id INT UNSIGNED NOT NULL,
+
+  PRIMARY KEY (field_id, editor_id),
+  FOREIGN KEY (field_id) REFERENCES FieldDef(id),
+  FOREIGN KEY (editor_id) REFERENCES User(user_id)
+) ENGINE=INNODB;
+
+
+ALTER TABLE FieldDef ADD COLUMN is_restricted_field BOOL DEFAULT FALSE;
+
+================================================================
+2020-05-14: Add option to force detailed notifications for projects.
+
+ALTER TABLE Project ADD COLUMN issue_notify_always_detailed BOOLEAN DEFAULT FALSE;
+