Subject: [PATCH v51 07/10] Check for transaction block early in ExecRepack

From: Srinath Reddy Sadipiralla <[email-masked]>
Date: Fri, 3 Apr 2026 20:53:56 +0530

Currently, executing REPACK (CONCURRENTLY) without a table name inside a
transaction block throws the error "REPACK CONCURRENTLY requires explicit
table name" instead of the expected transaction block error. This occurs
because ExecRepack() validates the parsed options and missing relation
before verifying the transaction state.

This behavior is inconsistent with other utility commands like VACUUM
,REINDEX, etc; which invoke PreventInTransactionBlock() at the very start
of their execution to properly reject execution inside user transactions
before validating targets.

Add PreventInTransactionBlock to the top of ExecRepack() to enforce the
transaction block restriction early. This prevents the user from fixing
a missing table error only to immediately hit a transaction block error,
and also ensures consistency with rest of the commands.

Author: Srinath Reddy Sadipiralla <[email-masked]>
---
 src/backend/commands/repack.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c
index d6e446d582d..d4c1f0e7652 100644
--- a/src/backend/commands/repack.c
+++ b/src/backend/commands/repack.c
@@ -292,6 +292,18 @@ ExecRepack(ParseState *pstate, RepackStmt *stmt, bool isTopLevel)
 		MyProc->statusFlags |= PROC_IN_CONCURRENT_REPACK;
 		ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
 		LWLockRelease(ProcArrayLock);
+
+		/*
+		 * Make sure we're not in a transaction block.
+		 *
+		 * The reason is that repack_setup_logical_decoding() could wait
+		 * indefinitely for our XID to complete. (The deadlock detector would
+		 * not recognize it because we'd be waiting for ourselves, i.e. no
+		 * real lock conflict.) It would be possible to run in a transaction
+		 * block if we had no XID, but this restriction is simpler for users
+		 * to understand and we don't lose anything.
+		 */
+		PreventInTransactionBlock(isTopLevel, "REPACK (CONCURRENTLY)");
 	}
 
 	/*
@@ -523,21 +535,7 @@ cluster_rel(RepackCommand cmd, Relation OldHeap, Oid indexOid,
 	 * replica index OID.
 	 */
 	if (concurrent)
-	{
-		/*
-		 * Make sure we're not in a transaction block.
-		 *
-		 * The reason is that repack_setup_logical_decoding() could wait
-		 * indefinitely for our XID to complete. (The deadlock detector would
-		 * not recognize it because we'd be waiting for ourselves, i.e. no
-		 * real lock conflict.) It would be possible to run in a transaction
-		 * block if we had no XID, but this restriction is simpler for users
-		 * to understand and we don't lose anything.
-		 */
-		PreventInTransactionBlock(isTopLevel, "REPACK (CONCURRENTLY)");
-
 		check_repack_concurrently_requirements(OldHeap, &ident_idx);
-	}
 
 	/* Check for user-requested abort. */
 	CHECK_FOR_INTERRUPTS();
-- 
2.47.3

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