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HOT updates. When we update a tuple without changing any of its indexed

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columns, and the new version can be stored on the same heap page, we no longer
generate extra index entries for the new version.  Instead, index searches
follow the HOT-chain links to ensure they find the correct tuple version.

In addition, this patch introduces the ability to "prune" dead tuples on a
per-page basis, without having to do a complete VACUUM pass to recover space.
VACUUM is still needed to clean up dead index entries, however.

Pavan Deolasee, with help from a bunch of other people.
This commit is contained in:
Tom Lane
2007-09-20 17:56:33 +00:00
parent bbf4fdc253
commit 282d2a03dd
65 changed files with 3517 additions and 514 deletions
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45
src/backend/optimizer/util/var.c
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@ -8,12 +8,13 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.70 2007/06/11 01:16:23 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.71 2007/09/20 17:56:31 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/htup.h"
#include "optimizer/clauses.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
@ -54,6 +55,7 @@ typedef struct
static bool pull_varnos_walker(Node *node,
pull_varnos_context *context);
static bool pull_varattnos_walker(Node *node, Bitmapset **varattnos);
static bool contain_var_reference_walker(Node *node,
contain_var_reference_context *context);
static bool contain_var_clause_walker(Node *node, void *context);
@ -134,6 +136,47 @@ pull_varnos_walker(Node *node, pull_varnos_context *context)
(void *) context);
}
/*
* pull_varattnos
* Find all the distinct attribute numbers present in an expression tree,
* and add them to the initial contents of *varattnos.
* Only Vars that reference RTE 1 of rtable level zero are considered.
*
* Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
* we can include system attributes (e.g., OID) in the bitmap representation.
*
* Currently, this does not support subqueries nor expressions containing
* references to multiple tables; not needed since it's only applied to
* index expressions and predicates.
*/
void
pull_varattnos(Node *node, Bitmapset **varattnos)
{
(void) pull_varattnos_walker(node, varattnos);
}
static bool
pull_varattnos_walker(Node *node, Bitmapset **varattnos)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
Var *var = (Var *) node;
Assert(var->varno == 1);
*varattnos = bms_add_member(*varattnos,
var->varattno - FirstLowInvalidHeapAttributeNumber);
return false;
}
/* Should not find a subquery or subplan */
Assert(!IsA(node, Query));
Assert(!is_subplan(node));
return expression_tree_walker(node, pull_varattnos_walker,
(void *) varattnos);
}
/*
* contain_var_reference