Fix up rickety handling of relation-truncation interlocks.

Move rd_targblock, rd_fsm_nblocks, and rd_vm_nblocks from relcache to the smgr
relation entries, so that they will get reset to InvalidBlockNumber whenever
an smgr-level flush happens.  Because we now send smgr invalidation messages
immediately (not at end of transaction) when a relation truncation occurs,
this ensures that other backends will reset their values before they next
access the relation.  We no longer need the unreliable assumption that a
VACUUM that's doing a truncation will hold its AccessExclusive lock until
commit --- in fact, we can intentionally release that lock as soon as we've
completed the truncation.  This patch therefore reverts (most of) Alvaro's
patch of 2009-11-10, as well as my marginal hacking on it yesterday.  We can
also get rid of assorted no-longer-needed relcache flushes, which are far more
expensive than an smgr flush because they kill a lot more state.

In passing this patch fixes smgr_redo's failure to perform visibility-map
truncation, and cleans up some rather dubious assumptions in freespace.c and
visibilitymap.c about when rd_fsm_nblocks and rd_vm_nblocks can be out of
date.

3 files changed, 35 insertions, 13 deletions

diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 6527aa72342..ef568e9dcd5 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.88 2010/02/08 04:33:54 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.89 2010/02/09 21:43:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -145,7 +145,7 @@ extern void vac_update_datfrozenxid(void);
 extern void vacuum_delay_point(void);
 
 /* in commands/vacuumlazy.c */
-extern bool lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
+extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 				BufferAccessStrategy bstrategy, bool *scanned_all);
 
 /* in commands/analyze.c */
diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h
index 3cf02776311..d7e267729d3 100644
--- a/src/include/storage/smgr.h
+++ b/src/include/storage/smgr.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/smgr.h,v 1.69 2010/01/02 16:58:08 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/smgr.h,v 1.70 2010/02/09 21:43:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -43,6 +43,17 @@ typedef struct SMgrRelationData
 	/* pointer to owning pointer, or NULL if none */
 	struct SMgrRelationData **smgr_owner;
 
+	/*
+	 * These next three fields are not actually used or manipulated by smgr,
+	 * except that they are reset to InvalidBlockNumber upon a cache flush
+	 * event (in particular, upon truncation of the relation).  Higher levels
+	 * store cached state here so that it will be reset when truncation
+	 * happens.  In all three cases, InvalidBlockNumber means "unknown".
+	 */
+	BlockNumber smgr_targblock;		/* current insertion target block */
+	BlockNumber smgr_fsm_nblocks;	/* last known size of fsm fork */
+	BlockNumber smgr_vm_nblocks;	/* last known size of vm fork */
+
 	/* additional public fields may someday exist here */
 
 	/*
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index c4a1fcf7b64..405ff18e0ba 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/rel.h,v 1.122 2010/02/07 20:48:13 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/rel.h,v 1.123 2010/02/09 21:43:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -125,8 +125,6 @@ typedef struct RelationData
 	RelFileNode rd_node;		/* relation physical identifier */
 	/* use "struct" here to avoid needing to include smgr.h: */
 	struct SMgrRelationData *rd_smgr;	/* cached file handle, or NULL */
-	BlockNumber rd_targblock;	/* current insertion target block, or
-								 * InvalidBlockNumber */
 	int			rd_refcnt;		/* reference count */
 	bool		rd_istemp;		/* rel is a temporary relation */
 	bool		rd_islocaltemp; /* rel is a temp rel of this session */
@@ -212,13 +210,6 @@ typedef struct RelationData
 	 */
 	Oid			rd_toastoid;	/* Real TOAST table's OID, or InvalidOid */
 
-	/*
-	 * sizes of the free space and visibility map forks, or InvalidBlockNumber
-	 * if not known yet
-	 */
-	BlockNumber rd_fsm_nblocks;
-	BlockNumber rd_vm_nblocks;
-
 	/* use "struct" here to avoid needing to include pgstat.h: */
 	struct PgStat_TableStatus *pgstat_info;		/* statistics collection area */
 } RelationData;
@@ -375,6 +366,26 @@ typedef struct StdRdOptions
 	} while (0)
 
 /*
+ * RelationGetTargetBlock
+ *		Fetch relation's current insertion target block.
+ *
+ * Returns InvalidBlockNumber if there is no current target block.  Note
+ * that the target block status is discarded on any smgr-level invalidation.
+ */
+#define RelationGetTargetBlock(relation) \
+	( (relation)->rd_smgr != NULL ? (relation)->rd_smgr->smgr_targblock : InvalidBlockNumber )
+
+/*
+ * RelationSetTargetBlock
+ *		Set relation's current insertion target block.
+ */
+#define RelationSetTargetBlock(relation, targblock) \
+	do { \
+		RelationOpenSmgr(relation); \
+		(relation)->rd_smgr->smgr_targblock = (targblock); \
+	} while (0)
+
+/*
  * RELATION_IS_LOCAL
  *		If a rel is either temp or newly created in the current transaction,
  *		it can be assumed to be visible only to the current backend.