Phase 2 of project to make index operator lossiness be determined at runtime

instead of plan time.  Extend the amgettuple API so that the index AM returns
a boolean indicating whether the indexquals need to be rechecked, and make
that rechecking happen in nodeIndexscan.c (currently the only place where
it's expected to be needed; other callers of index_getnext are just erroring
out for now).  For the moment, GIN and GIST have stub logic that just always
sets the recheck flag to TRUE --- I'm hoping to get Teodor to handle pushing
that control down to the opclass consistent() functions.  The planner no
longer pays any attention to amopreqcheck, and that catalog column will go
away in due course.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 637b363f528..cf8f8a0c4df 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/relscan.h,v 1.63 2008/04/12 23:14:21 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/relscan.h,v 1.64 2008/04/13 19:18:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -76,15 +76,16 @@ typedef struct IndexScanDescData
 	/* index access method's private state */
 	void	   *opaque;			/* access-method-specific info */
 
-	/* xs_ctup/xs_cbuf are valid after a successful index_getnext */
+	/* xs_ctup/xs_cbuf/xs_recheck are valid after a successful index_getnext */
 	HeapTupleData xs_ctup;		/* current heap tuple, if any */
 	Buffer		xs_cbuf;		/* current heap buffer in scan, if any */
 	/* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
+	bool		xs_recheck;		/* T means scan keys must be rechecked */
 
 	/* state data for traversing HOT chains in index_getnext */
-	TransactionId xs_prev_xmax; /* previous HOT chain member's XMAX, if any */
-	OffsetNumber xs_next_hot;	/* next member of HOT chain, if any */
 	bool		xs_hot_dead;	/* T if all members of HOT chain are dead */
+	OffsetNumber xs_next_hot;	/* next member of HOT chain, if any */
+	TransactionId xs_prev_xmax; /* previous HOT chain member's XMAX, if any */
 } IndexScanDescData;
 
 typedef IndexScanDescData *IndexScanDesc;