-
+
|
- amorderstrategy
- int2
-
- Zero if the index offers no sort order, otherwise the strategy
- number of the strategy operator that describes the default
- (ASC) sort order
-
-
- |
- amdescorder
- int2
+ amcanorder
+ bool
- Zero if the index offers no sort order, otherwise the strategy
- number of the strategy operator that describes the DESC
- sort order
+ Does the access method support ordered scans?
|
-
+
Index Access Method Interface Definition
the scan keys to a normalized form.
+ Some access methods return index entries in a well-defined order, others
+ do not. If entries are returned in sorted order, the access method should
+ set pg_am.amcanorder true to indicate that
+ it supports ordered scans.
+ All such access methods must use btree-compatible strategy numbers for
+ their equality and ordering operators.
+
+
The amgettuple function has a direction argument,
which can be either ForwardScanDirection (the normal case)
the normal front-to-back direction, so amgettuple must return
the last matching tuple in the index, rather than the first one as it
normally would. (This will only occur for access
- methods that advertise they support ordered scans by setting
- pg_am.amorderstrategy nonzero.) After the
+ methods that advertise they support ordered scans.) After the
first call, amgettuple must be prepared to advance the scan in
either direction from the most recently returned entry.
-
+
Interfacing Extensions To Indexes
return type boolean, since they must appear at the top
level of a WHERE clause to be used with an index.
-
- By the way, the amorderstrategy and
- amdescorder columns in pg_am tell
- whether the index method supports ordered scans. Zeroes mean it doesn't;
- if it does, amorderstrategy is the strategy
- number that corresponds to the default ordering operator, and
- amdescorder is the strategy number for the
- ordering operator of an index column that has the DESC option.
- For example, B-tree has amorderstrategy = 1,
- which is its less than
strategy number, and
- amdescorder = 5, which is its
- greater than
strategy number.
-
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/indexcmds.c,v 1.152 2007/01/09 02:14:11 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/indexcmds.c,v 1.153 2007/01/20 23:13:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
errmsg("access method \"%s\" does not support multicolumn indexes",
accessMethodName)));
- amcanorder = (accessMethodForm->amorderstrategy > 0);
-
+ amcanorder = accessMethodForm->amcanorder;
amoptions = accessMethodForm->amoptions;
ReleaseSysCache(tuple);
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.131 2007/01/09 02:14:13 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.132 2007/01/20 23:13:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/*
* Fetch the ordering operators associated with the index, if any.
+ * We expect that all ordering-capable indexes use btree's
+ * strategy numbers for the ordering operators.
*/
- if (indexRelation->rd_am->amorderstrategy > 0)
+ if (indexRelation->rd_am->amcanorder)
{
int nstrat = indexRelation->rd_am->amstrategies;
if (opt & INDOPTION_DESC)
{
- fwdstrat = indexRelation->rd_am->amdescorder;
- revstrat = indexRelation->rd_am->amorderstrategy;
+ fwdstrat = BTGreaterStrategyNumber;
+ revstrat = BTLessStrategyNumber;
}
else
{
- fwdstrat = indexRelation->rd_am->amorderstrategy;
- revstrat = indexRelation->rd_am->amdescorder;
+ fwdstrat = BTLessStrategyNumber;
+ revstrat = BTGreaterStrategyNumber;
}
/*
* Index AM must have a fixed set of strategies for it
- * to make sense to specify amorderstrategy, so we
+ * to make sense to specify amcanorder, so we
* need not allow the case amstrategies == 0.
*/
if (fwdstrat > 0)
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.244 2007/01/20 01:08:42 neilc Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.245 2007/01/20 23:13:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
&buf);
/* Add options if relevant */
- if (amrec->amorderstrategy > 0)
+ if (amrec->amcanorder)
{
/* if it supports sort ordering, report DESC and NULLS opts */
if (opt & INDOPTION_DESC)
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.374 2007/01/20 21:47:10 neilc Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.375 2007/01/20 23:13:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 200701202
+#define CATALOG_VERSION_NO 200701203
#endif
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/catalog/pg_am.h,v 1.49 2007/01/09 02:14:15 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_am.h,v 1.50 2007/01/20 23:13:01 tgl Exp $
*
* NOTES
* the genbki.sh script reads this file and generates .bki
* strategy assignments. */
int2 amsupport; /* total number of support functions that this
* AM uses */
- int2 amorderstrategy;/* if this AM has a sort order, the strategy
- * number of the default (ASC) sort operator.
- * Zero if AM is not ordered. */
- int2 amdescorder; /* if this AM has a sort order, the strategy
- * number of the DESC sort operator.
- * Zero if AM is not ordered. */
+ bool amcanorder; /* does AM support ordered scan results? */
bool amcanunique; /* does AM support UNIQUE indexes? */
bool amcanmulticol; /* does AM support multi-column indexes? */
bool amoptionalkey; /* can query omit key for the first column? */
* compiler constants for pg_am
* ----------------
*/
-#define Natts_pg_am 24
+#define Natts_pg_am 23
#define Anum_pg_am_amname 1
#define Anum_pg_am_amstrategies 2
#define Anum_pg_am_amsupport 3
-#define Anum_pg_am_amorderstrategy 4
-#define Anum_pg_am_amdescorder 5
-#define Anum_pg_am_amcanunique 6
-#define Anum_pg_am_amcanmulticol 7
-#define Anum_pg_am_amoptionalkey 8
-#define Anum_pg_am_amindexnulls 9
-#define Anum_pg_am_amstorage 10
-#define Anum_pg_am_amclusterable 11
-#define Anum_pg_am_aminsert 12
-#define Anum_pg_am_ambeginscan 13
-#define Anum_pg_am_amgettuple 14
-#define Anum_pg_am_amgetmulti 15
-#define Anum_pg_am_amrescan 16
-#define Anum_pg_am_amendscan 17
-#define Anum_pg_am_ammarkpos 18
-#define Anum_pg_am_amrestrpos 19
-#define Anum_pg_am_ambuild 20
-#define Anum_pg_am_ambulkdelete 21
-#define Anum_pg_am_amvacuumcleanup 22
-#define Anum_pg_am_amcostestimate 23
-#define Anum_pg_am_amoptions 24
+#define Anum_pg_am_amcanorder 4
+#define Anum_pg_am_amcanunique 5
+#define Anum_pg_am_amcanmulticol 6
+#define Anum_pg_am_amoptionalkey 7
+#define Anum_pg_am_amindexnulls 8
+#define Anum_pg_am_amstorage 9
+#define Anum_pg_am_amclusterable 10
+#define Anum_pg_am_aminsert 11
+#define Anum_pg_am_ambeginscan 12
+#define Anum_pg_am_amgettuple 13
+#define Anum_pg_am_amgetmulti 14
+#define Anum_pg_am_amrescan 15
+#define Anum_pg_am_amendscan 16
+#define Anum_pg_am_ammarkpos 17
+#define Anum_pg_am_amrestrpos 18
+#define Anum_pg_am_ambuild 19
+#define Anum_pg_am_ambulkdelete 20
+#define Anum_pg_am_amvacuumcleanup 21
+#define Anum_pg_am_amcostestimate 22
+#define Anum_pg_am_amoptions 23
/* ----------------
* initial contents of pg_am
* ----------------
*/
-DATA(insert OID = 403 ( btree 5 1 1 5 t t t t f t btinsert btbeginscan btgettuple btgetmulti btrescan btendscan btmarkpos btrestrpos btbuild btbulkdelete btvacuumcleanup btcostestimate btoptions ));
+DATA(insert OID = 403 ( btree 5 1 t t t t t f t btinsert btbeginscan btgettuple btgetmulti btrescan btendscan btmarkpos btrestrpos btbuild btbulkdelete btvacuumcleanup btcostestimate btoptions ));
DESCR("b-tree index access method");
#define BTREE_AM_OID 403
-DATA(insert OID = 405 ( hash 1 1 0 0 f f f f f f hashinsert hashbeginscan hashgettuple hashgetmulti hashrescan hashendscan hashmarkpos hashrestrpos hashbuild hashbulkdelete hashvacuumcleanup hashcostestimate hashoptions ));
+DATA(insert OID = 405 ( hash 1 1 f f f f f f f hashinsert hashbeginscan hashgettuple hashgetmulti hashrescan hashendscan hashmarkpos hashrestrpos hashbuild hashbulkdelete hashvacuumcleanup hashcostestimate hashoptions ));
DESCR("hash index access method");
#define HASH_AM_OID 405
-DATA(insert OID = 783 ( gist 0 7 0 0 f t t t t t gistinsert gistbeginscan gistgettuple gistgetmulti gistrescan gistendscan gistmarkpos gistrestrpos gistbuild gistbulkdelete gistvacuumcleanup gistcostestimate gistoptions ));
+DATA(insert OID = 783 ( gist 0 7 f f t t t t t gistinsert gistbeginscan gistgettuple gistgetmulti gistrescan gistendscan gistmarkpos gistrestrpos gistbuild gistbulkdelete gistvacuumcleanup gistcostestimate gistoptions ));
DESCR("GiST index access method");
#define GIST_AM_OID 783
-DATA(insert OID = 2742 ( gin 0 4 0 0 f f f f t f gininsert ginbeginscan gingettuple gingetmulti ginrescan ginendscan ginmarkpos ginrestrpos ginbuild ginbulkdelete ginvacuumcleanup gincostestimate ginoptions ));
+DATA(insert OID = 2742 ( gin 0 4 f f f f f t f gininsert ginbeginscan gingettuple gingetmulti ginrescan ginendscan ginmarkpos ginrestrpos ginbuild ginbulkdelete ginvacuumcleanup gincostestimate ginoptions ));
DESCR("GIN index access method");
#define GIN_AM_OID 2742
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