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/[email protected]

1 files changed, 73 insertions, 0 deletions

diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index ca44d39100a..7cc443ec520 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -455,6 +455,7 @@ 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,
@@ -1305,6 +1306,17 @@ 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 */
@@ -2498,6 +2510,67 @@ ExecEvalParamExtern(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
 }
 
 /*
+ * Evaluate a SQLValueFunction expression.
+ */
+void
+ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op)
+{
+	LOCAL_FCINFO(fcinfo, 0);
+	SQLValueFunction *svf = op->d.sqlvaluefunction.svf;
+
+	*op->resnull = false;
+
+	/*
+	 * Note: current_schema() can return NULL.  current_user() etc currently
+	 * cannot, but might as well code those cases the same way for safety.
+	 */
+	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;
+		case SVFOP_CURRENT_ROLE:
+		case SVFOP_CURRENT_USER:
+		case SVFOP_USER:
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = current_user(fcinfo);
+			*op->resnull = fcinfo->isnull;
+			break;
+		case SVFOP_SESSION_USER:
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = session_user(fcinfo);
+			*op->resnull = fcinfo->isnull;
+			break;
+		case SVFOP_CURRENT_CATALOG:
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = current_database(fcinfo);
+			*op->resnull = fcinfo->isnull;
+			break;
+		case SVFOP_CURRENT_SCHEMA:
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = current_schema(fcinfo);
+			*op->resnull = fcinfo->isnull;
+			break;
+	}
+}
+
+/*
  * Raise error if a CURRENT OF expression is evaluated.
  *
  * The planner should convert CURRENT OF into a TidScan qualification, or some