Get rid of ParseState.p_value_substitute; use a columnref hook instead.

I noticed that p_value_substitute, which is a single-purpose kluge I added
in 2002 (commit b0422b215), could be replaced by having domainAddConstraint
install a parser hook that looks for the name "value".  The parser hook
code only dates back to 2009, so it's not surprising that we had to kluge
this in 2002, but we can do it more cleanly now.

1 files changed, 33 insertions, 1 deletions

diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index c07babbe972..3ff6cbca56f 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -104,6 +104,8 @@ static char *domainAddConstraint(Oid domainOid, Oid domainNamespace,
 					Oid baseTypeOid,
 					int typMod, Constraint *constr,
 					char *domainName, ObjectAddress *constrAddr);
+static Node *replace_domain_constraint_value(ParseState *pstate,
+								ColumnRef *cref);
 
 
 /*
@@ -3022,7 +3024,8 @@ domainAddConstraint(Oid domainOid, Oid domainNamespace, Oid baseTypeOid,
 	domVal->collation = get_typcollation(baseTypeOid);
 	domVal->location = -1;		/* will be set when/if used */
 
-	pstate->p_value_substitute = (Node *) domVal;
+	pstate->p_pre_columnref_hook = replace_domain_constraint_value;
+	pstate->p_ref_hook_state = (void *) domVal;
 
 	expr = transformExpr(pstate, constr->raw_expr, EXPR_KIND_DOMAIN_CHECK);
 
@@ -3099,6 +3102,35 @@ domainAddConstraint(Oid domainOid, Oid domainNamespace, Oid baseTypeOid,
 	return ccbin;
 }
 
+/* Parser pre_columnref_hook for domain CHECK constraint parsing */
+static Node *
+replace_domain_constraint_value(ParseState *pstate, ColumnRef *cref)
+{
+	/*
+	 * Check for a reference to "value", and if that's what it is, replace
+	 * with a CoerceToDomainValue as prepared for us by domainAddConstraint.
+	 * (We handle VALUE as a name, not a keyword, to avoid breaking a lot of
+	 * applications that have used VALUE as a column name in the past.)
+	 */
+	if (list_length(cref->fields) == 1)
+	{
+		Node	   *field1 = (Node *) linitial(cref->fields);
+		char	   *colname;
+
+		Assert(IsA(field1, String));
+		colname = strVal(field1);
+		if (strcmp(colname, "value") == 0)
+		{
+			CoerceToDomainValue *domVal = copyObject(pstate->p_ref_hook_state);
+
+			/* Propagate location knowledge, if any */
+			domVal->location = cref->location;
+			return (Node *) domVal;
+		}
+	}
+	return NULL;
+}
+
 
 /*
  * Execute ALTER TYPE RENAME