Replace SQLValueFunction by COERCE_SQL_SYNTAX

This switch impacts 9 patterns related to a SQL-mandated special syntax
for function calls:
- LOCALTIME [ ( typmod ) ]
- LOCALTIMESTAMP [ ( typmod ) ]
- CURRENT_TIME [ ( typmod ) ]
- CURRENT_TIMESTAMP [ ( typmod ) ]
- CURRENT_DATE

Five new entries are added to pg_proc to compensate the removal of
SQLValueFunction to provide backward-compatibility and making this
change transparent for the end-user (for example for the attribute
generated when a keyword is specified in a SELECT or in a FROM clause
without an alias, or when specifying something else than an Iconst to
the parser).

The parser included a set of checks coming from the files in charge of
holding the C functions used for the SQLValueFunction calls (as of
transformSQLValueFunction()), which are now moved within each function's
execution path, so this reduces the dependencies between the execution
and the parsing steps.  As of this change, all the SQL keywords use the
same paths for their work, relying only on COERCE_SQL_SYNTAX.  Like
fb32748, no performance difference has been noticed, while the perf
profiles get reduced with ExecEvalSQLValueFunction() gone.

Bump catalog version.

Reviewed-by: Corey Huinker, Ted Yu
Discussion: https://postgr.es/m/YzaG3MoryCguUOym@paquier.xyz

Author: michaelpq

src/backend/catalog/system_functions.sql

@@ -594,6 +594,32 @@ LANGUAGE internal
 STRICT IMMUTABLE PARALLEL SAFE
 AS 'unicode_is_normalized';
 
+-- Functions with SQL-mandated special syntax and some defaults.
+CREATE OR REPLACE FUNCTION
+  "current_time"(int4 DEFAULT NULL)
+ RETURNS timetz
+ LANGUAGE internal
+ STABLE PARALLEL SAFE
+AS 'current_time';
+CREATE OR REPLACE FUNCTION
+  "current_timestamp"(int4 DEFAULT NULL)
+ RETURNS timestamptz
+ LANGUAGE internal
+ STABLE PARALLEL SAFE
+ AS 'current_timestamp';
+CREATE OR REPLACE FUNCTION
+  "localtime"(int4 DEFAULT NULL)
+ RETURNS time
+ LANGUAGE internal
+ STABLE PARALLEL SAFE
+ AS 'sql_localtime';
+CREATE OR REPLACE FUNCTION
+  "localtimestamp"(int4 DEFAULT NULL)
+ RETURNS timestamp
+ LANGUAGE internal
+ STABLE PARALLEL SAFE
+ AS 'sql_localtimestamp';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather

src/backend/executor/execExpr.c

@@ -2210,17 +2210,6 @@ ExecInitExprRec(Expr *node, ExprState *state,
 				break;
 			}
 
-		case T_SQLValueFunction:
-			{
-				SQLValueFunction *svf = (SQLValueFunction *) node;
-
-				scratch.opcode = EEOP_SQLVALUEFUNCTION;
-				scratch.d.sqlvaluefunction.svf = svf;
-
-				ExprEvalPushStep(state, &scratch);
-				break;
-			}
-
 		case T_XmlExpr:
 			{
 				XmlExpr    *xexpr = (XmlExpr *) node;

src/backend/executor/execExprInterp.c

@@ -452,7 +452,6 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_DISTINCT,
 		&&CASE_EEOP_NOT_DISTINCT,
 		&&CASE_EEOP_NULLIF,
-		&&CASE_EEOP_SQLVALUEFUNCTION,
 		&&CASE_EEOP_CURRENTOFEXPR,
 		&&CASE_EEOP_NEXTVALUEEXPR,
 		&&CASE_EEOP_ARRAYEXPR,
@@ -1301,17 +1300,6 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
-		EEO_CASE(EEOP_SQLVALUEFUNCTION)
-		{
-			/*
-			 * Doesn't seem worthwhile to have an inline implementation
-			 * efficiency-wise.
-			 */
-			ExecEvalSQLValueFunction(state, op);
-
-			EEO_NEXT();
-		}
-
 		EEO_CASE(EEOP_CURRENTOFEXPR)
 		{
 			/* error invocation uses space, and shouldn't ever occur */
@@ -2489,40 +2477,6 @@ ExecEvalParamExtern(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
 			 errmsg("no value found for parameter %d", paramId)));
 }
 
-/*
- * Evaluate a SQLValueFunction expression.
- */
-void
-ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op)
-{
-	SQLValueFunction *svf = op->d.sqlvaluefunction.svf;
-
-	*op->resnull = false;
-
-	switch (svf->op)
-	{
-		case SVFOP_CURRENT_DATE:
-			*op->resvalue = DateADTGetDatum(GetSQLCurrentDate());
-			break;
-		case SVFOP_CURRENT_TIME:
-		case SVFOP_CURRENT_TIME_N:
-			*op->resvalue = TimeTzADTPGetDatum(GetSQLCurrentTime(svf->typmod));
-			break;
-		case SVFOP_CURRENT_TIMESTAMP:
-		case SVFOP_CURRENT_TIMESTAMP_N:
-			*op->resvalue = TimestampTzGetDatum(GetSQLCurrentTimestamp(svf->typmod));
-			break;
-		case SVFOP_LOCALTIME:
-		case SVFOP_LOCALTIME_N:
-			*op->resvalue = TimeADTGetDatum(GetSQLLocalTime(svf->typmod));
-			break;
-		case SVFOP_LOCALTIMESTAMP:
-		case SVFOP_LOCALTIMESTAMP_N:
-			*op->resvalue = TimestampGetDatum(GetSQLLocalTimestamp(svf->typmod));
-			break;
-	}
-}
-
 /*
  * Raise error if a CURRENT OF expression is evaluated.
  *

src/backend/jit/llvm/llvmjit_expr.c

@@ -1549,12 +1549,6 @@ llvm_compile_expr(ExprState *state)
 					break;
 				}
 
-			case EEOP_SQLVALUEFUNCTION:
-				build_EvalXFunc(b, mod, "ExecEvalSQLValueFunction",
-								v_state, op);
-				LLVMBuildBr(b, opblocks[opno + 1]);
-				break;
-
 			case EEOP_CURRENTOFEXPR:
 				build_EvalXFunc(b, mod, "ExecEvalCurrentOfExpr",
 								v_state, op);

src/backend/jit/llvm/llvmjit_types.c

@@ -126,7 +126,6 @@ void	   *referenced_functions[] =
 	ExecEvalRow,
 	ExecEvalRowNotNull,
 	ExecEvalRowNull,
-	ExecEvalSQLValueFunction,
 	ExecEvalScalarArrayOp,
 	ExecEvalHashedScalarArrayOp,
 	ExecEvalSubPlan,

src/backend/nodes/nodeFuncs.c

@@ -210,9 +210,6 @@ exprType(const Node *expr)
 		case T_MinMaxExpr:
 			type = ((const MinMaxExpr *) expr)->minmaxtype;
 			break;
-		case T_SQLValueFunction:
-			type = ((const SQLValueFunction *) expr)->type;
-			break;
 		case T_XmlExpr:
 			if (((const XmlExpr *) expr)->op == IS_DOCUMENT)
 				type = BOOLOID;
@@ -474,8 +471,6 @@ exprTypmod(const Node *expr)
 				return typmod;
 			}
 			break;
-		case T_SQLValueFunction:
-			return ((const SQLValueFunction *) expr)->typmod;
 		case T_CoerceToDomain:
 			return ((const CoerceToDomain *) expr)->resulttypmod;
 		case T_CoerceToDomainValue:
@@ -916,10 +911,6 @@ exprCollation(const Node *expr)
 		case T_MinMaxExpr:
 			coll = ((const MinMaxExpr *) expr)->minmaxcollid;
 			break;
-		case T_SQLValueFunction:
-			/* Returns a non-collatable type */
-			coll = InvalidOid;
-			break;
 		case T_XmlExpr:
 
 			/*
@@ -1140,9 +1131,6 @@ exprSetCollation(Node *expr, Oid collation)
 		case T_MinMaxExpr:
 			((MinMaxExpr *) expr)->minmaxcollid = collation;
 			break;
-		case T_SQLValueFunction:
-			Assert(collation == InvalidOid);
-			break;
 		case T_XmlExpr:
 			Assert((((XmlExpr *) expr)->op == IS_XMLSERIALIZE) ?
 				   (collation == DEFAULT_COLLATION_OID) :
@@ -1426,10 +1414,6 @@ exprLocation(const Node *expr)
 			/* GREATEST/LEAST keyword should always be the first thing */
 			loc = ((const MinMaxExpr *) expr)->location;
 			break;
-		case T_SQLValueFunction:
-			/* function keyword should always be the first thing */
-			loc = ((const SQLValueFunction *) expr)->location;
-			break;
 		case T_XmlExpr:
 			{
 				const XmlExpr *xexpr = (const XmlExpr *) expr;
@@ -1717,10 +1701,10 @@ set_sa_opfuncid(ScalarArrayOpExpr *opexpr)
  * for themselves, in case additional checks should be made, or because they
  * have special rules about which parts of the tree need to be visited.
  *
- * Note: we ignore MinMaxExpr, SQLValueFunction, XmlExpr, CoerceToDomain,
- * and NextValueExpr nodes, because they do not contain SQL function OIDs.
- * However, they can invoke SQL-visible functions, so callers should take
- * thought about how to treat them.
+ * Note: we ignore MinMaxExpr, XmlExpr, CoerceToDomain, and NextValueExpr
+ * nodes, because they do not contain SQL function OIDs.  However, they can
+ * invoke SQL-visible functions, so callers should take thought about how
+ * to treat them.
  */
 bool
 check_functions_in_node(Node *node, check_function_callback checker,
@@ -1936,7 +1920,6 @@ expression_tree_walker_impl(Node *node,
 		case T_Const:
 		case T_Param:
 		case T_CaseTestExpr:
-		case T_SQLValueFunction:
 		case T_CoerceToDomainValue:
 		case T_SetToDefault:
 		case T_CurrentOfExpr:
@@ -2673,7 +2656,6 @@ expression_tree_mutator_impl(Node *node,
 			break;
 		case T_Param:
 		case T_CaseTestExpr:
-		case T_SQLValueFunction:
 		case T_CoerceToDomainValue:
 		case T_SetToDefault:
 		case T_CurrentOfExpr:
@@ -3587,7 +3569,6 @@ raw_expression_tree_walker_impl(Node *node,
 	{
 		case T_SetToDefault:
 		case T_CurrentOfExpr:
-		case T_SQLValueFunction:
 		case T_Integer:
 		case T_Float:
 		case T_Boolean:

src/backend/optimizer/path/costsize.c

@@ -4603,7 +4603,6 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context)
 		}
 	}
 	else if (IsA(node, MinMaxExpr) ||
-			 IsA(node, SQLValueFunction) ||
 			 IsA(node, XmlExpr) ||
 			 IsA(node, CoerceToDomain) ||
 			 IsA(node, NextValueExpr))

src/backend/optimizer/util/clauses.c

@@ -383,12 +383,6 @@ contain_mutable_functions_walker(Node *node, void *context)
 								context))
 		return true;
 
-	if (IsA(node, SQLValueFunction))
-	{
-		/* all variants of SQLValueFunction are stable */
-		return true;
-	}
-
 	if (IsA(node, NextValueExpr))
 	{
 		/* NextValueExpr is volatile */
@@ -537,8 +531,8 @@ contain_volatile_functions_walker(Node *node, void *context)
 
 	/*
 	 * See notes in contain_mutable_functions_walker about why we treat
-	 * MinMaxExpr, XmlExpr, and CoerceToDomain as immutable, while
-	 * SQLValueFunction is stable.  Hence, none of them are of interest here.
+	 * MinMaxExpr, XmlExpr, and CoerceToDomain as immutable.  Hence, none of
+	 * them are of interest here.
 	 */
 
 	/* Recurse to check arguments */
@@ -583,10 +577,9 @@ contain_volatile_functions_not_nextval_walker(Node *node, void *context)
 
 	/*
 	 * See notes in contain_mutable_functions_walker about why we treat
-	 * MinMaxExpr, XmlExpr, and CoerceToDomain as immutable, while
-	 * SQLValueFunction is stable.  Hence, none of them are of interest here.
-	 * Also, since we're intentionally ignoring nextval(), presumably we
-	 * should ignore NextValueExpr.
+	 * MinMaxExpr, XmlExpr, and CoerceToDomain as immutable.  Hence, none of
+	 * them are of interest here.  Also, since we're intentionally ignoring
+	 * nextval(), presumably we should ignore NextValueExpr.
 	 */
 
 	/* Recurse to check arguments */
@@ -732,8 +725,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
 	 * (Note: in principle that's wrong because a domain constraint could
 	 * contain a parallel-unsafe function; but useful constraints probably
 	 * never would have such, and assuming they do would cripple use of
-	 * parallel query in the presence of domain types.)  SQLValueFunction
-	 * should be safe in all cases.  NextValueExpr is parallel-unsafe.
+	 * parallel query in the presence of domain types.)  NextValueExpr is
+	 * parallel-unsafe.
 	 */
 	if (IsA(node, CoerceToDomain))
 	{
@@ -1180,7 +1173,6 @@ contain_leaked_vars_walker(Node *node, void *context)
 		case T_CaseExpr:
 		case T_CaseTestExpr:
 		case T_RowExpr:
-		case T_SQLValueFunction:
 		case T_NullTest:
 		case T_BooleanTest:
 		case T_NextValueExpr:
@@ -3194,23 +3186,6 @@ eval_const_expressions_mutator(Node *node,
 				newcoalesce->location = coalesceexpr->location;
 				return (Node *) newcoalesce;
 			}
-		case T_SQLValueFunction:
-			{
-				/*
-				 * All variants of SQLValueFunction are stable, so if we are
-				 * estimating the expression's value, we should evaluate the
-				 * current function value.  Otherwise just copy.
-				 */
-				SQLValueFunction *svf = (SQLValueFunction *) node;
-
-				if (context->estimate)
-					return (Node *) evaluate_expr((Expr *) svf,
-												  svf->type,
-												  svf->typmod,
-												  InvalidOid);
-				else
-					return copyObject((Node *) svf);
-			}
 		case T_FieldSelect:
 			{
 				/*