Add CHECK_FOR_INTERRUPTS in ExecInsert's speculative insertion loop.

tglsfdc · tglsfdc · commit 23edf0e8b4d1 · 2022-08-04T14:10:06.000-04:00
Ordinarily the functions called in this loop ought to have plenty of CFIs themselves; but we've now seen a case where no such CFI is reached, making the loop uninterruptible. Even though that's from a recently-introduced bug, it seems prudent to install a CFI at the loop level in all branches. Per discussion of bug #17558 from Andrew Kesper (an actual fix for that bug will follow). Discussion: https://postgr.es/m/17558-3f6599ffcf52fd4a@postgresql.org
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
@@ -541,9 +541,11 @@ ExecInsert(ModifyTableState *mtstate,
 			 *
 			 * We loop back here if we find a conflict below, either during
 			 * the pre-check, or when we re-check after inserting the tuple
-			 * speculatively.
+			 * speculatively.  Better allow interrupts in case some bug makes
+			 * this an infinite loop.
 			 */
 	vlock:
+			CHECK_FOR_INTERRUPTS();
 			specConflict = false;
 			if (!ExecCheckIndexConstraints(slot, estate, &conflictTid,
 										   arbiterIndexes))
