v10-0001-Add-DomainHasVolatileConstraints-to-check-constraint-volatility.patch

From 070da693d0aaba70b452b40776200b7b0698df86 Mon Sep 17 00:00:00 2001
From: jian he <jian.universality@gmail.com>
Date: Wed, 11 Mar 2026 10:04:13 +0800
Subject: [PATCH v10 1/2] Add DomainHasVolatileConstraints() to check
 constraint volatility

Add a utility function that checks whether a domain type has any
constraints, and optionally whether any CHECK constraint contains
volatile expressions.  This is needed by a subsequent commit that
enables the fast default optimization for domains with non-volatile
constraints: we can safely evaluate such constraints once at ALTER TABLE
time, but volatile constraints require a full table rewrite.

Discussion: https://postgr.es/m/CACJufxE_+iZBR1i49k_AHigppPwLTJi6km8NOsC7FWvKdEmmXg@mail.gmail.com
Commitfest: https://commitfest.postgresql.org/patch/5641
---
 src/backend/utils/cache/typcache.c | 45 ++++++++++++++++++++++++++++++
 src/include/utils/typcache.h       |  1 +
 2 files changed, 46 insertions(+)

diff --git a/src/backend/utils/cache/typcache.c b/src/backend/utils/cache/typcache.c
index 627e534609a..e33d4b807bd 100644
--- a/src/backend/utils/cache/typcache.c
+++ b/src/backend/utils/cache/typcache.c
@@ -1502,6 +1502,51 @@ DomainHasConstraints(Oid type_id)
 }
 
 
+/*
+ * DomainHasVolatileConstraints --- check if a domain has constraints with
+ * volatile expressions
+ *
+ * Returns true if the domain has any constraints at all.  If have_volatile
+ * is not NULL, also checks whether any CHECK constraint contains a volatile
+ * expression and sets *have_volatile accordingly.
+ *
+ * The caller must initialize *have_volatile before calling (typically to
+ * false).  This function only ever sets it to true, never to false.
+ *
+ * This is defined to return false, not fail, if type is not a domain.
+ */
+bool
+DomainHasVolatileConstraints(Oid type_id, bool *have_volatile)
+{
+	/*
+	 * Note: a side effect is to cause the typcache's domain data to become
+	 * valid.  This is fine since we'll likely need it soon if there is any.
+	 */
+	TypeCacheEntry *typentry = lookup_type_cache(type_id, TYPECACHE_DOMAIN_CONSTR_INFO);
+
+	if (typentry->domainData != NULL)
+	{
+		if (have_volatile)
+		{
+			foreach_node(DomainConstraintState, constrstate,
+						 typentry->domainData->constraints)
+			{
+				if (constrstate->constrainttype == DOM_CONSTRAINT_CHECK &&
+					contain_volatile_functions((Node *) constrstate->check_expr))
+				{
+					*have_volatile = true;
+					break;
+				}
+			}
+		}
+
+		return true;
+	}
+
+	return false;
+}
+
+
 /*
  * array_element_has_equality and friends are helper routines to check
  * whether we should believe that array_eq and related functions will work
diff --git a/src/include/utils/typcache.h b/src/include/utils/typcache.h
index 0e3945aa244..38366ff159e 100644
--- a/src/include/utils/typcache.h
+++ b/src/include/utils/typcache.h
@@ -184,6 +184,7 @@ extern void InitDomainConstraintRef(Oid type_id, DomainConstraintRef *ref,
 extern void UpdateDomainConstraintRef(DomainConstraintRef *ref);
 
 extern bool DomainHasConstraints(Oid type_id);
+extern bool DomainHasVolatileConstraints(Oid type_id, bool *have_volatile);
 
 extern TupleDesc lookup_rowtype_tupdesc(Oid type_id, int32 typmod);
 
-- 
2.34.1