Teach planner to expand sufficiently simple SQL-language functions

('SELECT expression') inline, like macros, during the constant-folding
phase of planning.  The actual expansion is not difficult, but checking
that we're not changing the semantics of the call turns out to be more
subtle than one might think; in particular must pay attention to
permissions issues, strictness, and volatility.

1 files changed, 38 insertions, 1 deletions

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index cd7dc8d549f..ec0c45ea78a 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.86 2002/11/25 21:29:42 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/lsyscache.c,v 1.87 2002/12/01 21:05:14 tgl Exp $
  *
  * NOTES
  *	  Eventually, the index information should go through here, too.
@@ -416,6 +416,22 @@ op_hashjoinable(Oid opno, Oid ltype, Oid rtype)
 }
 
 /*
+ * op_strict
+ *
+ * Get the proisstrict flag for the operator's underlying function.
+ */
+bool
+op_strict(Oid opno)
+{
+	RegProcedure funcid = get_opcode(opno);
+
+	if (funcid == (RegProcedure) InvalidOid)
+		elog(ERROR, "Operator OID %u does not exist", opno);
+
+	return func_strict((Oid) funcid);
+}
+
+/*
  * op_volatile
  *
  * Get the provolatile flag for the operator's underlying function.
@@ -607,6 +623,27 @@ get_func_retset(Oid funcid)
 }
 
 /*
+ * func_strict
+ *		Given procedure id, return the function's proisstrict flag.
+ */
+bool
+func_strict(Oid funcid)
+{
+	HeapTuple	tp;
+	bool		result;
+
+	tp = SearchSysCache(PROCOID,
+						ObjectIdGetDatum(funcid),
+						0, 0, 0);
+	if (!HeapTupleIsValid(tp))
+		elog(ERROR, "Function OID %u does not exist", funcid);
+
+	result = ((Form_pg_proc) GETSTRUCT(tp))->proisstrict;
+	ReleaseSysCache(tp);
+	return result;
+}
+
+/*
  * func_volatile
  *		Given procedure id, return the function's provolatile flag.
  */