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Commit606c012

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Reduce btree scan overhead for < and > strategies
For <, <=, > and >= strategies, mark the first scan keyas already matched if scanning in an appropriate direction.If index tuple contains no nulls we can skip the firstre-check for each tuple.Author: Rajeev RastogiReviewer: Haribabu KommiRework of the code and comments by Simon Riggs
1 parentdedae6c commit606c012

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3 files changed

+35
-0
lines changed

3 files changed

+35
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‎src/backend/access/nbtree/nbtsearch.c

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Original file line numberDiff line numberDiff line change
@@ -996,6 +996,33 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
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if (goback)
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offnum=OffsetNumberPrev(offnum);
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/*
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* By here the scan position is now set for the first key. If all
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* further tuples are expected to match we set the SK_BT_MATCHED flag
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* to avoid re-checking the scan key later. This is a big win for
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* slow key matches though is still significant even for fast datatypes.
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*/
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switch (startKeys[0]->sk_strategy)
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{
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caseBTEqualStrategyNumber:
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break;
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caseBTGreaterEqualStrategyNumber:
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caseBTGreaterStrategyNumber:
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if (ScanDirectionIsForward(dir))
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startKeys[0]->sk_flags |=SK_BT_MATCHED;
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break;
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caseBTLessEqualStrategyNumber:
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caseBTLessStrategyNumber:
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if (ScanDirectionIsBackward(dir))
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startKeys[0]->sk_flags |=SK_BT_MATCHED;
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break;
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default:
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break;
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}
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/*
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* Now load data from the first page of the scan.
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*/

‎src/backend/access/nbtree/nbtutils.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1429,6 +1429,13 @@ _bt_checkkeys(IndexScanDesc scan,
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boolisNull;
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Datumtest;
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/*
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* If the scan key has already matched we can skip this key, as
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* long as the index tuple does not contain NULL values.
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*/
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if (key->sk_flags&SK_BT_MATCHED&& !IndexTupleHasNulls(tuple))
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continue;
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/* row-comparison keys need special processing */
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if (key->sk_flags&SK_ROW_HEADER)
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{

‎src/include/access/nbtree.h

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Original file line numberDiff line numberDiff line change
@@ -618,6 +618,7 @@ typedef BTScanOpaqueData *BTScanOpaque;
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*/
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#defineSK_BT_REQFWD0x00010000/* required to continue forward scan */
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#defineSK_BT_REQBKWD0x00020000/* required to continue backward scan */
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#defineSK_BT_MATCHED0x00040000/* required to skip further key match */
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#defineSK_BT_INDOPTION_SHIFT 24/* must clear the above bits */
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#defineSK_BT_DESC(INDOPTION_DESC << SK_BT_INDOPTION_SHIFT)
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#defineSK_BT_NULLS_FIRST(INDOPTION_NULLS_FIRST << SK_BT_INDOPTION_SHIFT)

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