postgres.git / summary / log / commit / refs
commit 3a97460970f344660971ee75d7f5a181bf87f633
Author: Amit Langote <amitlan@postgresql.org>
Date: Fri Sep 06 03:05:40 2024 +0000
First released in: master (reverted before release), REL_17_STABLE (reverted before release)
Reverted by: eef5195f300b (in 17.0), 4d7e24e0f4d0 (in 18.0)
SQL/JSON: Avoid initializing unnecessary ON ERROR / ON EMPTY steps
When the ON ERROR / ON EMPTY behavior is to return NULL, returning
NULL directly from ExecEvalJsonExprPath() suffices. Therefore, there's
no need to create separate steps to check the error/empty flag or
those to evaluate the the constant NULL expression. This speeds up
common cases because the default ON ERROR / ON EMPTY behavior for
JSON_QUERY() and JSON_VALUE() is to return NULL. However, these steps
are necessary if the RETURNING type is a domain, as constraints on the
domain may need to be checked.
Reported-by: Jian He <jian.universality@gmail.com>
Author: Jian He <jian.universality@gmail.com>
Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com
Backpatch-through: 17
src/backend/executor/execExpr.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index 63289ee35ee..4d247538bea 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -4414,6 +4414,8 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
ErrorSaveContext *escontext =
jsexpr->on_error->btype != JSON_BEHAVIOR_ERROR ?
&jsestate->escontext : NULL;
+ bool returning_domain =
+ get_typtype(jsexpr->returning->typid) == TYPTYPE_DOMAIN;
jsestate->jsexpr = jsexpr;
@@ -4556,20 +4558,27 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
ExprEvalPushStep(state, scratch);
}
- jsestate->jump_empty = jsestate->jump_error = -1;
-
/*
* Step to check jsestate->error and return the ON ERROR expression if
* there is one. This handles both the errors that occur during jsonpath
* evaluation in EEOP_JSONEXPR_PATH and subsequent coercion evaluation.
+ *
+ * Speed up common cases by avoiding extra steps for a NULL-valued ON
+ * ERROR expression unless RETURNING a domain type, where constraints must
+ * be checked. ExecEvalJsonExprPath() already returns NULL on error,
+ * making additional steps unnecessary in typical scenarios. Note that the
+ * default ON ERROR behavior for JSON_VALUE() and JSON_QUERY() is to
+ * return NULL.
*/
+ jsestate->jump_error = state->steps_len;
if (jsexpr->on_error &&
- jsexpr->on_error->btype != JSON_BEHAVIOR_ERROR)
+ jsexpr->on_error->btype != JSON_BEHAVIOR_ERROR &&
+ (!(IsA(jsexpr->on_error->expr, Const) &&
+ ((Const *) jsexpr->on_error->expr)->constisnull) ||
+ returning_domain))
{
ErrorSaveContext *saved_escontext;
- jsestate->jump_error = state->steps_len;
-
/* JUMP to end if false, that is, skip the ON ERROR expression. */
jumps_to_end = lappend_int(jumps_to_end, state->steps_len);
scratch->opcode = EEOP_JUMP_IF_NOT_TRUE;
@@ -4619,14 +4628,19 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
/*
* Step to check jsestate->empty and return the ON EMPTY expression if
* there is one.
+ *
+ * See the comment above for details on the optimization for NULL-valued
+ * expressions.
*/
+ jsestate->jump_empty = state->steps_len;
if (jsexpr->on_empty != NULL &&
- jsexpr->on_empty->btype != JSON_BEHAVIOR_ERROR)
+ jsexpr->on_empty->btype != JSON_BEHAVIOR_ERROR &&
+ (!(IsA(jsexpr->on_empty->expr, Const) &&
+ ((Const *) jsexpr->on_empty->expr)->constisnull) ||
+ returning_domain))
{
ErrorSaveContext *saved_escontext;
- jsestate->jump_empty = state->steps_len;
-
/* JUMP to end if false, that is, skip the ON EMPTY expression. */
jumps_to_end = lappend_int(jumps_to_end, state->steps_len);
scratch->opcode = EEOP_JUMP_IF_NOT_TRUE;
[parent: 565caaa79af9]