From 079526f201136c32be42774b8eec5c829ab728b2 Mon Sep 17 00:00:00 2001
From: jian he <jian.universality@gmail.com>
Date: Thu, 13 Mar 2025 15:05:41 +0800
Subject: [PATCH v4 3/4] soft error variant of ExecPrepareExpr, ExecInitExpr

ExecPrepareExprSafe and ExecInitExprSafe.
ExecPrepareExprSafe initialize for expression execution with soft error support.
not all expression node support it. some like CoerceToDomain do support it.

XXX more comments.

discussion: https://postgr.es/m/CACJufxE_+iZBR1i49k_AHigppPwLTJi6km8NOsC7FWvKdEmmXg@mail.gmail.com
---
 src/backend/executor/execExpr.c | 63 +++++++++++++++++++++++++++++++++
 src/include/executor/executor.h |  2 ++
 2 files changed, 65 insertions(+)

diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index f1569879b52..b8f5f647281 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -170,6 +170,46 @@ ExecInitExpr(Expr *node, PlanState *parent)
 	return state;
 }
 
+/*
+ * ExecInitExpr: soft error variant of ExecInitExpr.
+ * use it only for expression nodes support soft errors, not all expression
+ * nodes support it.
+*/
+ExprState *
+ExecInitExprSafe(Expr *node, PlanState *parent)
+{
+	ExprState  *state;
+	ExprEvalStep scratch = {0};
+
+	/* Special case: NULL expression produces a NULL ExprState pointer */
+	if (node == NULL)
+		return NULL;
+
+	/* Initialize ExprState with empty step list */
+	state = makeNode(ExprState);
+	state->expr = node;
+	state->parent = parent;
+	state->ext_params = NULL;
+	state->escontext = makeNode(ErrorSaveContext);
+	state->escontext->type = T_ErrorSaveContext;
+	state->escontext->error_occurred = false;
+	state->escontext->details_wanted = true;
+
+	/* Insert setup steps as needed */
+	ExecCreateExprSetupSteps(state, (Node *) node);
+
+	/* Compile the expression proper */
+	ExecInitExprRec(node, state, &state->resvalue, &state->resnull);
+
+	/* Finally, append a DONE step */
+	scratch.opcode = EEOP_DONE_RETURN;
+	ExprEvalPushStep(state, &scratch);
+
+	ExecReadyExpr(state);
+
+	return state;
+}
+
 /*
  * ExecInitExprWithParams: prepare a standalone expression tree for execution
  *
@@ -778,6 +818,29 @@ ExecPrepareExpr(Expr *node, EState *estate)
 	return result;
 }
 
+/*
+ * ExecPrepareExprSafe: soft error variant of ExecPrepareExpr.
+ *
+ * use it when expression node *support* soft error expression execution.
+ * ExecPrepareExpr comments apply to here too.
+ */
+ExprState *
+ExecPrepareExprSafe(Expr *node, EState *estate)
+{
+	ExprState  *result;
+	MemoryContext oldcontext;
+
+	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+	node = expression_planner(node);
+
+	result = ExecInitExprSafe(node, NULL);
+
+	MemoryContextSwitchTo(oldcontext);
+
+	return result;
+}
+
 /*
  * ExecPrepareQual --- initialize for qual execution outside a normal
  * Plan tree context.
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 4063ed68f5f..28e7df4f336 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -309,6 +309,7 @@ ExecProcNode(PlanState *node)
  * prototypes from functions in execExpr.c
  */
 extern ExprState *ExecInitExpr(Expr *node, PlanState *parent);
+extern ExprState *ExecInitExprSafe(Expr *node, PlanState *parent);
 extern ExprState *ExecInitExprWithParams(Expr *node, ParamListInfo ext_params);
 extern ExprState *ExecInitQual(List *qual, PlanState *parent);
 extern ExprState *ExecInitCheck(List *qual, PlanState *parent);
@@ -357,6 +358,7 @@ extern ProjectionInfo *ExecBuildUpdateProjection(List *targetList,
 												 TupleTableSlot *slot,
 												 PlanState *parent);
 extern ExprState *ExecPrepareExpr(Expr *node, EState *estate);
+extern ExprState *ExecPrepareExprSafe(Expr *node, EState *estate);
 extern ExprState *ExecPrepareQual(List *qual, EState *estate);
 extern ExprState *ExecPrepareCheck(List *qual, EState *estate);
 extern List *ExecPrepareExprList(List *nodes, EState *estate);
-- 
2.34.1