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Improve dynahash.c's API so that caller can specify the comparison function
as well as the hash function (formerly the comparison function was hardwired as memcmp()). This makes it possible to eliminate the special-purpose hashtable management code in execGrouping.c in favor of using dynahash to manage tuple hashtables; which is a win because dynahash knows how to expand a hashtable when the original size estimate was too small, whereas the special-purpose code was too stupid to do that. (See recent gripe from Stephan Szabo about poor performance when hash table size estimate is way off.) Free side benefit: when using string_hash, the default comparison function is now strncmp() instead of memcmp(). This should eliminate some part of the overhead associated with larger NAMEDATALEN values.
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src
backend
include
test
regress
expected
@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: executor.h,v 1.99 2003/08/08 21:42:44 momjian Exp $
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* $Id: executor.h,v 1.100 2003/08/19 01:13:41 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -71,8 +71,6 @@ extern TupleHashTable BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
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extern TupleHashEntry LookupTupleHashEntry(TupleHashTable hashtable,
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TupleTableSlot *slot,
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bool *isnew);
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extern TupleHashEntry ScanTupleHashTable(TupleHashTable hashtable,
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TupleHashIterator *state);
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/*
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* prototypes from functions in execJunk.c
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