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, 6 insertions, 1 deletions

diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index 56a16401f35..021c2daf26d 100644
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -10,7 +10,7 @@
  * Copyright (c) 2002-2009, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.99 2009/08/10 05:46:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.100 2009/11/04 22:26:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -379,6 +379,11 @@ EvaluateParams(PreparedStatement *pstmt, List *params,
 	paramLI = (ParamListInfo)
 		palloc(sizeof(ParamListInfoData) +
 			   (num_params - 1) *sizeof(ParamExternData));
+	/* we have static list of params, so no hooks needed */
+	paramLI->paramFetch = NULL;
+	paramLI->paramFetchArg = NULL;
+	paramLI->parserSetup = NULL;
+	paramLI->parserSetupArg = NULL;
 	paramLI->numParams = num_params;
 
 	i = 0;