Add support for invoking parser callback hooks via SPI and in cached plans.

As proof of concept, modify plpgsql to use the hooks.  plpgsql is still
inserting $n symbols textually, but the "back end" of the parsing process now
goes through the ParamRef hook instead of using a fixed parameter-type array,
and then execution only fetches actually-referenced parameters, using a hook
added to ParamListInfo.

Although there's a lot left to be done in plpgsql, this already cures the
"if (TG_OP = 'INSERT' and NEW.foo ...)"  problem, as illustrated by the
changed regression test.

1 files changed, 14 insertions, 2 deletions

diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index fdfbd999f4f..226e15546fd 100644
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.253 2009/10/26 02:26:29 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.254 2009/11/04 22:26:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -882,9 +882,21 @@ ExecEvalParam(ExprState *exprstate, ExprContext *econtext,
 		{
 			ParamExternData *prm = &paramInfo->params[thisParamId - 1];
 
+			/* give hook a chance in case parameter is dynamic */
+			if (!OidIsValid(prm->ptype) && paramInfo->paramFetch != NULL)
+				(*paramInfo->paramFetch) (paramInfo, thisParamId);
+
 			if (OidIsValid(prm->ptype))
 			{
-				Assert(prm->ptype == expression->paramtype);
+				/* safety check in case hook did something unexpected */
+				if (prm->ptype != expression->paramtype)
+					ereport(ERROR,
+							(errcode(ERRCODE_DATATYPE_MISMATCH),
+							 errmsg("type of parameter %d (%s) does not match that when preparing the plan (%s)",
+									thisParamId,
+									format_type_be(prm->ptype),
+									format_type_be(expression->paramtype))));
+
 				*isNull = prm->isnull;
 				return prm->value;
 			}