Add back SQLValueFunction for SQL keywords

This is equivalent to a revert of f193883 and fb32748, with the addition
that the declaration of the SQLValueFunction node needs to gain a couple
of node_attr for query jumbling.  The performance impact of removing the
function call inlining is proving to be too huge for some workloads
where these are used.  A worst-case test case of involving only simple
SELECT queries with a SQL keyword is proving to lead to a reduction of
10% in TPS via pgbench and prepared queries on a high-end machine.

None of the tests I ran back for this set of changes saw such a huge
gap, but Alexander Lakhin and Andres Freund have found that this can be
noticeable.  Keeping the older performance would mean to do more
inlining in the executor when using COERCE_SQL_SYNTAX for a function
expression, similarly to what SQLValueFunction does.  This requires more
redesign work and there is little time until 16beta1 is released, so for
now reverting the change is the best way forward, bringing back the
previous performance.

Bump catalog version.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/b32bed1b-0746-9b20-1472-4bdc9ca66d52@gmail.com

1 files changed, 29 insertions, 37 deletions

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index aaadc68ae6a..0e50aaec5a5 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -83,6 +83,27 @@ static Timestamp timestamptz2timestamp(TimestampTz timestamp);
 
 /* common code for timestamptypmodin and timestamptztypmodin */
 static int32
+anytimestamp_typmodin(bool istz, ArrayType *ta)
+{
+	int32	   *tl;
+	int			n;
+
+	tl = ArrayGetIntegerTypmods(ta, &n);
+
+	/*
+	 * we're not too tense about good error message here because grammar
+	 * shouldn't allow wrong number of modifiers for TIMESTAMP
+	 */
+	if (n != 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid type modifier")));
+
+	return anytimestamp_typmod_check(istz, tl[0]);
+}
+
+/* exported so parse_expr.c can use it */
+int32
 anytimestamp_typmod_check(bool istz, int32 typmod)
 {
 	if (typmod < 0)
@@ -103,26 +124,6 @@ anytimestamp_typmod_check(bool istz, int32 typmod)
 	return typmod;
 }
 
-static int32
-anytimestamp_typmodin(bool istz, ArrayType *ta)
-{
-	int32	   *tl;
-	int			n;
-
-	tl = ArrayGetIntegerTypmods(ta, &n);
-
-	/*
-	 * we're not too tense about good error message here because grammar
-	 * shouldn't allow wrong number of modifiers for TIMESTAMP
-	 */
-	if (n != 1)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("invalid type modifier")));
-
-	return anytimestamp_typmod_check(istz, tl[0]);
-}
-
 /* common code for timestamptypmodout and timestamptztypmodout */
 static char *
 anytimestamp_typmodout(bool istz, int32 typmod)
@@ -1594,42 +1595,33 @@ GetCurrentTimestamp(void)
 }
 
 /*
- * current_timestamp -- implements CURRENT_TIMESTAMP, CURRENT_TIMESTAMP(n)
+ * GetSQLCurrentTimestamp -- implements CURRENT_TIMESTAMP, CURRENT_TIMESTAMP(n)
  */
-Datum
-current_timestamp(PG_FUNCTION_ARGS)
+TimestampTz
+GetSQLCurrentTimestamp(int32 typmod)
 {
 	TimestampTz ts;
-	int32		typmod = -1;
-
-	if (!PG_ARGISNULL(0))
-		typmod = anytimestamp_typmod_check(true, PG_GETARG_INT32(0));
 
 	ts = GetCurrentTransactionStartTimestamp();
 	if (typmod >= 0)
 		AdjustTimestampForTypmod(&ts, typmod, NULL);
-	return TimestampTzGetDatum(ts);
+	return ts;
 }
 
 /*
- * sql_localtimestamp -- implements LOCALTIMESTAMP, LOCALTIMESTAMP(n)
+ * GetSQLLocalTimestamp -- implements LOCALTIMESTAMP, LOCALTIMESTAMP(n)
  */
-Datum
-sql_localtimestamp(PG_FUNCTION_ARGS)
+Timestamp
+GetSQLLocalTimestamp(int32 typmod)
 {
 	Timestamp	ts;
-	int32		typmod = -1;
-
-	if (!PG_ARGISNULL(0))
-		typmod = anytimestamp_typmod_check(false, PG_GETARG_INT32(0));
 
 	ts = timestamptz2timestamp(GetCurrentTransactionStartTimestamp());
 	if (typmod >= 0)
 		AdjustTimestampForTypmod(&ts, typmod, NULL);
-	return TimestampGetDatum(ts);
+	return ts;
 }
 
-
 /*
  * timeofday(*) -- returns the current time as a text.
  */