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Redesign DISTINCT ON as discussed in pgsql-sql 1/25/00: syntax is now

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SELECT DISTINCT ON (expr [, expr ...]) targetlist ...
and there is a check to make sure that the user didn't specify an ORDER BY
that's incompatible with the DISTINCT operation.
Reimplement nodeUnique and nodeGroup to use the proper datatype-specific
equality function for each column being compared --- they used to do
bitwise comparisons or convert the data to text strings and strcmp().
(To add insult to injury, they'd look up the conversion functions once
for each tuple...)  Parse/plan representation of DISTINCT is now a list
of SortClause nodes.
initdb forced by querytree change...
This commit is contained in:
Tom Lane
2000-01-27 18:11:50 +00:00
parent 3f0074e403
commit dd979f66be
32 changed files with 638 additions and 576 deletions
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16
src/include/nodes/execnodes.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: execnodes.h,v 1.39 2000/01/26 05:58:15 momjian Exp $
* $Id: execnodes.h,v 1.40 2000/01/27 18:11:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -621,6 +621,7 @@ typedef struct AggState
typedef struct GroupState
{
CommonScanState csstate; /* its first field is NodeTag */
FmgrInfo *eqfunctions; /* per-field lookup data for equality fns */
bool grp_useFirstTuple; /* first tuple not processed yet */
bool grp_done;
HeapTuple grp_firstTuple;
@ -663,9 +664,9 @@ typedef struct SortState
* Unique nodes are used "on top of" sort nodes to discard
* duplicate tuples returned from the sort phase. Basically
* all it does is compare the current tuple from the subplan
* with the previously fetched tuple stored in OuterTuple and
* if the two are identical, then we just fetch another tuple
* from the sort and try again.
* with the previously fetched tuple stored in priorTuple.
* If the two are identical in all interesting fields, then
* we just fetch another tuple from the sort and try again.
*
* CommonState information
*
@ -677,7 +678,12 @@ typedef struct SortState
* ScanAttributes attribute numbers of interest in this tuple
* ----------------
*/
typedef CommonState UniqueState;
typedef struct UniqueState
{
CommonState cstate; /* its first field is NodeTag */
FmgrInfo *eqfunctions; /* per-field lookup data for equality fns */
HeapTuple priorTuple; /* most recently returned tuple, or NULL */
} UniqueState;
/* ----------------