Fix determination when slot types for upper executor nodes are fixed.

anarazel · anarazel · commit 6cf74f1bbd65 · 2019-09-29T15:46:18.000-07:00
For many queries the fact that the tuple descriptor from the lower node was not taken into account when determining whether the type of a slot is fixed, lead to tuple deforming for such upper nodes not to be JIT accelerated. I broke this in 675af5c. There is ongoing work to enable writing regression tests for related behavior (including a patch that would have detected this regression), by optionally showing such details in EXPLAIN. But as it seems unlikely that that will be suitable for stable branches, just merge the fix for now. While it's fairly close to the 12 release window, the fact that 11 continues to perform JITed tuple deforming in these cases, that there's still cases where we do so in 12, and the fact that the performance regression can be sizable, weigh in favor of fixing it now. Author: Andres Freund Discussion: https://postgr.es/m/20190927072053.njf6prdl3vb7y7qb@alap3.anarazel.de Backpatch: 12-, where 675af5c was merged.
diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
@@ -2394,6 +2394,7 @@ ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
 		{
 			isfixed = true;
 			tts_ops = parent->innerops;
+			desc = ExecGetResultType(is);
 		}
 		else if (is)
 		{
@@ -2413,6 +2414,7 @@ ExecComputeSlotInfo(ExprState *state, ExprEvalStep *op)
 		{
 			isfixed = true;
 			tts_ops = parent->outerops;
+			desc = ExecGetResultType(os);
 		}
 		else if (os)
 		{

Original file line number	Diff line number	Diff line change
`@@ -2394,6 +2394,7 @@ ExecComputeSlotInfo(ExprState state, ExprEvalStep op)`
`2394`	`2394`	`{`
`2395`	`2395`	`isfixed = true;`
`2396`	`2396`	`tts_ops = parent->innerops;`
	`2397`	`+ desc = ExecGetResultType(is);`
`2397`	`2398`	`}`
`2398`	`2399`	`else if (is)`
`2399`	`2400`	`{`
`@@ -2413,6 +2414,7 @@ ExecComputeSlotInfo(ExprState state, ExprEvalStep op)`
`2413`	`2414`	`{`
`2414`	`2415`	`isfixed = true;`
`2415`	`2416`	`tts_ops = parent->outerops;`
	`2417`	`+ desc = ExecGetResultType(os);`
`2416`	`2418`	`}`
`2417`	`2419`	`else if (os)`
`2418`	`2420`	`{`