From 8037429545f83d568772b16928f20e7c1044154f Mon Sep 17 00:00:00 2001 From: Amit Langote Date: Thu, 5 Sep 2024 21:56:40 +0900 Subject: [PATCH v3 4/4] SQL/JSON: Avoid initializing unnecessary ON ERROR / ON EMPTY steps When the ON ERROR / ON EMPTY behavior is to return NULL (the default for JSON_VALUE() and JSON_QUERY()), 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. 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 Author: Jian He Author: Amit Langote Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com --- 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 63289ee35e..4d247538be 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; -- 2.43.0