MM-43770: Rename to Threads.ThreadDeleteAt (#20074)

Old versions of the Mattermost server did not qualify queries scanning both `Posts` and `Threads`, and choke on the ambiguity in deciding between the new `DeleteAt` on `Threads` and the `DeleteAt` on `Posts` in existing queries.

While this problem is transient only while running multiple server versions, it effectively makes our backwards compatibility guarantee void, not to mention complicating cloud deployments.

Work around this by renaming `Threads.DeleteAt` to `Threads.ThreadDeleteAt`. The old migration is nulled out, but remains, since some test servers have already upgraded and manually fixing each affected instance would be problematic. Thew new migration takes care of removing the old column -- if it ever existed.

Fixes: https://mattermost.atlassian.net/browse/MM-43770

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

db/migrations/mysql/000081_threads_deleteat.down.sql

@@ -1,14 +1 @@
-SET @preparedStatement = (SELECT IF(
-    EXISTS(
-        SELECT 1 FROM INFORMATION_SCHEMA.STATISTICS
-        WHERE table_name = 'Threads'
-        AND table_schema = DATABASE()
-        AND column_name = 'DeleteAt'
-    ) > 0,
-    'ALTER TABLE Threads DROP COLUMN DeleteAt;',
-    'SELECT 1;'
-));
-
-PREPARE removeColumnIfExists FROM @preparedStatement;
-EXECUTE removeColumnIfExists;
-DEALLOCATE PREPARE removeColumnIfExists;
+-- Replaced by 000083_threads_threaddeleteat.down.sql

db/migrations/mysql/000081_threads_deleteat.up.sql

@@ -1,19 +1 @@
-SET @preparedStatement = (SELECT IF(
-    NOT EXISTS(
-        SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
-        WHERE table_name = 'Threads'
-        AND table_schema = DATABASE()
-        AND column_name = 'DeleteAt'
-    ),
-    'ALTER TABLE Threads ADD COLUMN DeleteAt bigint(20);',
-    'SELECT 1;'
-));
-
-PREPARE addColumnIfNotExists FROM @preparedStatement;
-EXECUTE addColumnIfNotExists;
-DEALLOCATE PREPARE addColumnIfNotExists;
-
-UPDATE Threads, Posts
-SET Threads.DeleteAt = Posts.DeleteAt
-WHERE Posts.Id = Threads.PostId
-AND Threads.DeleteAt IS NULL;
+-- Replaced by 000083_threads_threaddeleteat.up.sql

db/migrations/mysql/000083_threads_threaddeleteat.down.sql

@@ -0,0 +1,14 @@
+SET @preparedStatement = (SELECT IF(
+    EXISTS(
+        SELECT 1 FROM INFORMATION_SCHEMA.STATISTICS
+        WHERE table_name = 'Threads'
+        AND table_schema = DATABASE()
+        AND column_name = 'ThreadDeleteAt'
+    ) > 0,
+    'ALTER TABLE Threads DROP COLUMN ThreadDeleteAt;',
+    'SELECT 1;'
+));
+
+PREPARE removeColumnIfExists FROM @preparedStatement;
+EXECUTE removeColumnIfExists;
+DEALLOCATE PREPARE removeColumnIfExists;

db/migrations/mysql/000083_threads_threaddeleteat.up.sql

@@ -0,0 +1,35 @@
+-- Drop any existing DeleteAt column from 000081_threads_deleteat.up.sql
+SET @preparedStatement = (SELECT IF(
+    EXISTS(
+        SELECT 1 FROM INFORMATION_SCHEMA.STATISTICS
+        WHERE table_name = 'Threads'
+        AND table_schema = DATABASE()
+        AND column_name = 'DeleteAt'
+    ) > 0,
+    'ALTER TABLE Threads DROP COLUMN DeleteAt;',
+    'SELECT 1;'
+));
+
+PREPARE removeColumnIfExists FROM @preparedStatement;
+EXECUTE removeColumnIfExists;
+DEALLOCATE PREPARE removeColumnIfExists;
+
+SET @preparedStatement = (SELECT IF(
+    NOT EXISTS(
+        SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
+        WHERE table_name = 'Threads'
+        AND table_schema = DATABASE()
+        AND column_name = 'ThreadDeleteAt'
+    ),
+    'ALTER TABLE Threads ADD COLUMN ThreadDeleteAt bigint(20);',
+    'SELECT 1;'
+));
+
+PREPARE addColumnIfNotExists FROM @preparedStatement;
+EXECUTE addColumnIfNotExists;
+DEALLOCATE PREPARE addColumnIfNotExists;
+
+UPDATE Threads, Posts
+SET Threads.ThreadDeleteAt = Posts.DeleteAt
+WHERE Posts.Id = Threads.PostId
+AND Threads.ThreadDeleteAt IS NULL;

db/migrations/postgres/000081_threads_deleteat.down.sql

@@ -1 +1 @@
-ALTER TABLE threads DROP COLUMN IF EXISTS deleteat;
+-- Replaced by 000083_threads_threaddeleteat.down.sql

db/migrations/postgres/000081_threads_deleteat.up.sql

@@ -1,2 +1 @@
-ALTER TABLE threads ADD COLUMN IF NOT EXISTS deleteat bigint;
-UPDATE threads SET deleteat = posts.deleteat FROM posts WHERE threads.deleteat IS NULL AND posts.id = threads.postid;
+-- Replaced by 000083_threads_threaddeleteat.up.sql

db/migrations/postgres/000083_threads_threaddeleteat.down.sql

@@ -0,0 +1 @@
+ALTER TABLE threads DROP COLUMN IF EXISTS threaddeleteat;

db/migrations/postgres/000083_threads_threaddeleteat.up.sql

@@ -0,0 +1,5 @@
+-- Drop any existing DeleteAt column from 000081_threads_deleteat.up.sql
+ALTER TABLE threads DROP COLUMN IF EXISTS deleteat;
+
+ALTER TABLE threads ADD COLUMN IF NOT EXISTS threaddeleteat bigint;
+UPDATE threads SET threaddeleteat = posts.deleteat FROM posts WHERE threads.threaddeleteat IS NULL AND posts.id = threads.postid;

model/thread.go

@@ -23,7 +23,8 @@ type Thread struct {
 	// to newest. Note that the root post author is not included in this list until they reply.
 	Participants StringArray `json:"participants"`
 
-	// DeleteAt is a denormalized copy of the root posts's DeleteAt.
+	// DeleteAt is a denormalized copy of the root posts's DeleteAt. In the database, it's
+	// named ThreadDeleteAt to avoid introducing a query conflict with older server versions.
 	DeleteAt int64 `json:"delete_at"`
 }
 

store/sqlstore/post_store.go

@@ -2605,7 +2605,7 @@ func (s *SqlPostStore) permanentDeleteThreads(transaction *sqlxTxWrapper, postId
 func (s *SqlPostStore) deleteThread(transaction *sqlxTxWrapper, postId string, deleteAtTime int64) error {
 	queryString, args, err := s.getQueryBuilder().
 		Update("Threads").
-		Set("DeleteAt", deleteAtTime).
+		Set("ThreadDeleteAt", deleteAtTime).
 		Where(sq.Eq{"PostId": postId}).
 		ToSql()
 	if err != nil {
@@ -2701,7 +2701,7 @@ func (s *SqlPostStore) updateThreadsFromPosts(transaction *sqlxTxWrapper, posts
 			"Threads.ReplyCount",
 			"Threads.LastReplyAt",
 			"Threads.Participants",
-			"COALESCE(Threads.DeleteAt, 0) AS DeleteAt",
+			"COALESCE(Threads.ThreadDeleteAt, 0) AS DeleteAt",
 		).
 		From("Threads").
 		Where(sq.Eq{"Threads.PostId": rootIds}).

store/sqlstore/thread_store.go

@@ -50,7 +50,7 @@ func (s *SqlThreadStore) initializeQueries() {
 			"Threads.ReplyCount",
 			"Threads.LastReplyAt",
 			"Threads.Participants",
-			"COALESCE(Threads.DeleteAt, 0) AS DeleteAt",
+			"COALESCE(Threads.ThreadDeleteAt, 0) AS DeleteAt",
 		).
 		From("Threads")
 
@@ -61,7 +61,7 @@ func (s *SqlThreadStore) initializeQueries() {
 			"Threads.ReplyCount",
 			"Threads.LastReplyAt",
 			"Threads.Participants",
-			"COALESCE(Threads.DeleteAt, 0) AS ThreadDeleteAt",
+			"COALESCE(Threads.ThreadDeleteAt, 0) AS ThreadDeleteAt",
 		).
 		From("Threads")
 }
@@ -107,7 +107,7 @@ func (s *SqlThreadStore) getTotalThreadsQuery(userId, teamId string, opts model.
 	}
 
 	if !opts.Deleted {
-		query = query.Where(sq.Eq{"COALESCE(Threads.DeleteAt, 0)": 0})
+		query = query.Where(sq.Eq{"COALESCE(Threads.ThreadDeleteAt, 0)": 0})
 	}
 
 	return query
@@ -180,7 +180,7 @@ func (s *SqlThreadStore) GetTotalUnreadMentions(userId, teamId string, opts mode
 	}
 
 	if !opts.Deleted {
-		query = query.Where(sq.Eq{"COALESCE(Threads.DeleteAt, 0)": 0})
+		query = query.Where(sq.Eq{"COALESCE(Threads.ThreadDeleteAt, 0)": 0})
 	}
 
 	sql, args, err := query.ToSql()
@@ -256,8 +256,8 @@ func (s *SqlThreadStore) GetThreadsForUser(userId, teamId string, opts model.Get
 
 	if !opts.Deleted {
 		query = query.Where(sq.Or{
-			sq.Eq{"Threads.DeleteAt": nil},
-			sq.Eq{"Threads.DeleteAt": 0},
+			sq.Eq{"Threads.ThreadDeleteAt": nil},
+			sq.Eq{"Threads.ThreadDeleteAt": 0},
 		})
 	}
 
@@ -352,7 +352,7 @@ func (s *SqlThreadStore) GetTeamsUnreadForUser(userID string, teamIDs []string)
 		sq.Eq{"ThreadMemberships.UserId": userID},
 		sq.Eq{"ThreadMemberships.Following": true},
 		sq.Eq{"Channels.TeamId": teamIDs},
-		sq.Eq{"COALESCE(Threads.DeleteAt, 0)": 0},
+		sq.Eq{"COALESCE(Threads.ThreadDeleteAt, 0)": 0},
 	}
 
 	var wg sync.WaitGroup