database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-11 10:01:57 +03:00
Code Activity

Redesign internal logic of nodeLimit so that it does not need to fetch

Browse Source 
one more row from the subplan than the COUNT would appear to require.
This costs a little more logic but a number of people have complained
about the old implementation.
This commit is contained in:
Tom Lane
2002-11-22 22:10:01 +00:00
parent 95c9c22633
commit e760d22391
2 changed files with 161 additions and 86 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
src/include/nodes/execnodes.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: execnodes.h,v 1.78 2002/11/15 02:50:10 momjian Exp $
* $Id: execnodes.h,v 1.79 2002/11/22 22:10:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -775,17 +775,28 @@ typedef struct SetOpState
* offset is the number of initial tuples to skip (0 does nothing).
* count is the number of tuples to return after skipping the offset tuples.
* If no limit count was specified, count is undefined and noCount is true.
* When lstate == LIMIT_INITIAL, offset/count/noCount haven't been set yet.
* ----------------
*/
typedef enum
{
LIMIT_INITIAL, /* initial state for LIMIT node */
LIMIT_EMPTY, /* there are no returnable rows */
LIMIT_INWINDOW, /* have returned a row in the window */
LIMIT_SUBPLANEOF, /* at EOF of subplan (within window) */
LIMIT_WINDOWEND, /* stepped off end of window */
LIMIT_WINDOWSTART /* stepped off beginning of window */
} LimitStateCond;
typedef struct LimitState
{
CommonState cstate; /* its first field is NodeTag */
long offset; /* current OFFSET value */
long count; /* current COUNT, if any */
long position; /* 1-based index of last tuple fetched */
bool parmsSet; /* have we calculated offset/limit yet? */
bool noCount; /* if true, ignore count */
bool atEnd; /* if true, we've reached EOF of subplan */
LimitStateCond lstate; /* state machine status, as above */
long position; /* 1-based index of last tuple returned */
TupleTableSlot *subSlot; /* tuple last obtained from subplan */
} LimitState;