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Support "x IS NOT NULL" clauses as indexscan conditions. This turns out

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to be just a minor extension of the previous patch that made "x IS NULL"
indexable, because we can treat the IS NOT NULL condition as if it were
"x < NULL" or "x > NULL" (depending on the index's NULLS FIRST/LAST option),
just like IS NULL is treated like "x = NULL".  Aside from any possible
usefulness in its own right, this is an important improvement for
index-optimized MAX/MIN aggregates: it is now reliably possible to get
a column's min or max value cheaply, even when there are a lot of nulls
cluttering the interesting end of the index.
This commit is contained in:
Tom Lane
2010-01-01 21:53:49 +00:00
parent 15faca2596
commit 29c4ad9829
18 changed files with 295 additions and 120 deletions
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25
src/include/access/skey.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/skey.h,v 1.37 2009/01/01 17:23:56 momjian Exp $
* $PostgreSQL: pgsql/src/include/access/skey.h,v 1.38 2010/01/01 21:53:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -52,11 +52,13 @@ typedef uint16 StrategyNumber;
* the operator. When using a ScanKey in a heap scan, these fields are not
* used and may be set to InvalidStrategy/InvalidOid.
*
* A ScanKey can also represent a condition "column IS NULL"; this is signaled
* by the SK_SEARCHNULL flag bit. In this case the argument is always NULL,
* A ScanKey can also represent a condition "column IS NULL" or "column
* IS NOT NULL"; these cases are signaled by the SK_SEARCHNULL and
* SK_SEARCHNOTNULL flag bits respectively. The argument is always NULL,
* and the sk_strategy, sk_subtype, and sk_func fields are not used (unless
* set by the index AM). Currently, SK_SEARCHNULL is supported only for
* index scans, not heap scans; and not all index AMs support it.
* set by the index AM). Currently, SK_SEARCHNULL and SK_SEARCHNOTNULL are
* supported only for index scans, not heap scans; and not all index AMs
* support them.
*
* Note: in some places, ScanKeys are used as a convenient representation
* for the invocation of an access method support procedure. In this case
@ -112,12 +114,13 @@ typedef ScanKeyData *ScanKey;
* bits should be defined here). Bits 16-31 are reserved for use within
* individual index access methods.
*/
#define SK_ISNULL 0x0001 /* sk_argument is NULL */
#define SK_UNARY 0x0002 /* unary operator (currently unsupported) */
#define SK_ROW_HEADER 0x0004 /* row comparison header (see above) */
#define SK_ROW_MEMBER 0x0008 /* row comparison member (see above) */
#define SK_ROW_END 0x0010 /* last row comparison member (see above) */
#define SK_SEARCHNULL 0x0020 /* scankey represents a "col IS NULL" qual */
#define SK_ISNULL 0x0001 /* sk_argument is NULL */
#define SK_UNARY 0x0002 /* unary operator (not supported!) */
#define SK_ROW_HEADER 0x0004 /* row comparison header (see above) */
#define SK_ROW_MEMBER 0x0008 /* row comparison member (see above) */
#define SK_ROW_END 0x0010 /* last row comparison member */
#define SK_SEARCHNULL 0x0020 /* scankey represents "col IS NULL" */
#define SK_SEARCHNOTNULL 0x0040 /* scankey represents "col IS NOT NULL" */
/*