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

6 files changed, 60 insertions, 27 deletions

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index d10cc28b0c..e617381bf4 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202305121
+#define CATALOG_VERSION_NO	202305171
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index b2bc81b15f..d7a60b39b5 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -1505,38 +1505,12 @@
 { oid => '745', descr => 'current user name',
   proname => 'current_user', provolatile => 's', prorettype => 'name',
   proargtypes => '', prosrc => 'current_user' },
-{ oid => '9695', descr => 'current role name',
-  proname => 'current_role', provolatile => 's', prorettype => 'name',
-  proargtypes => '', prosrc => 'current_user' },
-{ oid => '9696', descr => 'user name',
-  proname => 'user', provolatile => 's', prorettype => 'name',
-  proargtypes => '', prosrc => 'current_user' },
-{ oid => '9697', descr => 'name of the current database',
-  proname => 'current_catalog', provolatile => 's', prorettype => 'name',
-  proargtypes => '', prosrc => 'current_database' },
 { oid => '746', descr => 'session user name',
   proname => 'session_user', provolatile => 's', prorettype => 'name',
   proargtypes => '', prosrc => 'session_user' },
 { oid => '9977', descr => 'system user name',
   proname => 'system_user', provolatile => 's', prorettype => 'text',
   proargtypes => '', prosrc => 'system_user' },
-{ oid => '9978', descr => 'current date',
-  proname => 'current_date', provolatile => 's', prorettype => 'date',
-  proargtypes => '', prosrc => 'current_date' },
-{ oid => '9979', descr => 'current time',
-  proname => 'current_time', proisstrict => 'f', provolatile => 's',
-  prorettype => 'timetz', proargtypes => 'int4', prosrc => 'current_time' },
-{ oid => '9980', descr => 'current timestamp',
-  proname => 'current_timestamp', proisstrict => 'f', provolatile => 's',
-  prorettype => 'timestamptz', proargtypes => 'int4',
-  prosrc => 'current_timestamp' },
-{ oid => '9981', descr => 'local time',
-  proname => 'localtime', proisstrict => 'f', provolatile => 's',
-  prorettype => 'time', proargtypes => 'int4', prosrc => 'sql_localtime' },
-{ oid => '9982', descr => 'local timestamp',
-  proname => 'localtimestamp', proisstrict => 'f', provolatile => 's',
-  prorettype => 'timestamp', proargtypes => 'int4',
-  prosrc => 'sql_localtimestamp' },
 
 { oid => '744',
   proname => 'array_eq', prorettype => 'bool',
diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index 157b0d85f2..048573c2bc 100644
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -171,6 +171,7 @@ typedef enum ExprEvalOp
 	EEOP_DISTINCT,
 	EEOP_NOT_DISTINCT,
 	EEOP_NULLIF,
+	EEOP_SQLVALUEFUNCTION,
 	EEOP_CURRENTOFEXPR,
 	EEOP_NEXTVALUEEXPR,
 	EEOP_ARRAYEXPR,
@@ -418,6 +419,12 @@ typedef struct ExprEvalStep
 			FunctionCallInfo fcinfo_data_in;
 		}			iocoerce;
 
+		/* for EEOP_SQLVALUEFUNCTION */
+		struct
+		{
+			SQLValueFunction *svf;
+		}			sqlvaluefunction;
+
 		/* for EEOP_NEXTVALUEEXPR */
 		struct
 		{
@@ -769,6 +776,7 @@ extern void ExecEvalParamExec(ExprState *state, ExprEvalStep *op,
 							  ExprContext *econtext);
 extern void ExecEvalParamExtern(ExprState *state, ExprEvalStep *op,
 								ExprContext *econtext);
+extern void ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op);
 extern void ExecEvalCurrentOfExpr(ExprState *state, ExprEvalStep *op);
 extern void ExecEvalNextValueExpr(ExprState *state, ExprEvalStep *op);
 extern void ExecEvalRowNull(ExprState *state, ExprEvalStep *op,
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index be9c29f0bf..08e7dae73f 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1446,6 +1446,49 @@ typedef struct MinMaxExpr
 } MinMaxExpr;
 
 /*
+ * SQLValueFunction - parameterless functions with special grammar productions
+ *
+ * The SQL standard categorizes some of these as <datetime value function>
+ * and others as <general value specification>.  We call 'em SQLValueFunctions
+ * for lack of a better term.  We store type and typmod of the result so that
+ * some code doesn't need to know each function individually, and because
+ * we would need to store typmod anyway for some of the datetime functions.
+ * Note that currently, all variants return non-collating datatypes, so we do
+ * not need a collation field; also, all these functions are stable.
+ */
+typedef enum SQLValueFunctionOp
+{
+	SVFOP_CURRENT_DATE,
+	SVFOP_CURRENT_TIME,
+	SVFOP_CURRENT_TIME_N,
+	SVFOP_CURRENT_TIMESTAMP,
+	SVFOP_CURRENT_TIMESTAMP_N,
+	SVFOP_LOCALTIME,
+	SVFOP_LOCALTIME_N,
+	SVFOP_LOCALTIMESTAMP,
+	SVFOP_LOCALTIMESTAMP_N,
+	SVFOP_CURRENT_ROLE,
+	SVFOP_CURRENT_USER,
+	SVFOP_USER,
+	SVFOP_SESSION_USER,
+	SVFOP_CURRENT_CATALOG,
+	SVFOP_CURRENT_SCHEMA
+} SQLValueFunctionOp;
+
+typedef struct SQLValueFunction
+{
+	Expr		xpr;
+	SQLValueFunctionOp op;		/* which function this is */
+	/*
+	 * Result type/typmod.  Type is fully determined by "op", so no need to
+	 * include this Oid in the query jumbling.
+	 */
+	Oid			type pg_node_attr(query_jumble_ignore);
+	int32		typmod;
+	int			location;		/* token location, or -1 if unknown */
+} SQLValueFunction;
+
+/*
  * XmlExpr - various SQL/XML functions requiring special grammar productions
  *
  * 'name' carries the "NAME foo" argument (already XML-escaped).
diff --git a/src/include/utils/date.h b/src/include/utils/date.h
index 5fd886b3db..97e1a02121 100644
--- a/src/include/utils/date.h
+++ b/src/include/utils/date.h
@@ -96,6 +96,7 @@ TimeTzADTPGetDatum(const TimeTzADT *X)
 
 
 /* date.c */
+extern int32 anytime_typmod_check(bool istz, int32 typmod);
 extern double date2timestamp_no_overflow(DateADT dateVal);
 extern Timestamp date2timestamp_opt_overflow(DateADT dateVal, int *overflow);
 extern TimestampTz date2timestamptz_opt_overflow(DateADT dateVal, int *overflow);
@@ -103,6 +104,9 @@ extern int32 date_cmp_timestamp_internal(DateADT dateVal, Timestamp dt2);
 extern int32 date_cmp_timestamptz_internal(DateADT dateVal, TimestampTz dt2);
 
 extern void EncodeSpecialDate(DateADT dt, char *str);
+extern DateADT GetSQLCurrentDate(void);
+extern TimeTzADT *GetSQLCurrentTime(int32 typmod);
+extern TimeADT GetSQLLocalTime(int32 typmod);
 extern int	time2tm(TimeADT time, struct pg_tm *tm, fsec_t *fsec);
 extern int	timetz2tm(TimeTzADT *time, struct pg_tm *tm, fsec_t *fsec, int *tzp);
 extern int	tm2time(struct pg_tm *tm, fsec_t fsec, TimeADT *result);
diff --git a/src/include/utils/timestamp.h b/src/include/utils/timestamp.h
index edd59dc432..c4dd96c8c9 100644
--- a/src/include/utils/timestamp.h
+++ b/src/include/utils/timestamp.h
@@ -95,7 +95,11 @@ extern PGDLLIMPORT TimestampTz PgReloadTime;
 
 /* Internal routines (not fmgr-callable) */
 
+extern int32 anytimestamp_typmod_check(bool istz, int32 typmod);
+
 extern TimestampTz GetCurrentTimestamp(void);
+extern TimestampTz GetSQLCurrentTimestamp(int32 typmod);
+extern Timestamp GetSQLLocalTimestamp(int32 typmod);
 extern void TimestampDifference(TimestampTz start_time, TimestampTz stop_time,
 								long *secs, int *microsecs);
 extern long TimestampDifferenceMilliseconds(TimestampTz start_time,