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The trunk assumes that an open range constraint on an indexed term (col>?) term matches 1/4 of the indexed rows, and that a closed constraint (col BETWEEN ? AND ?) matches 1/64. Change this branch to do the same.

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FossilOrigin-Name: 4047ac75e2a8f0b330255501c42e4f04e5ab500d
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dan
2014-04-28 19:34:06 +00:00
parent 6b6828625b
commit 42685f211e
3 changed files with 13 additions and 7 deletions
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6
src/where.c
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@@ -2155,6 +2155,12 @@ static int whereRangeScanEst(
assert( pLower || pUpper );
nNew = whereRangeAdjust(pLower, nOut);
nNew = whereRangeAdjust(pUpper, nNew);
/* TUNING: If there is both an upper and lower limit, assume the range is
** reduced by an additional 75%. This means that, by default, an open-ended
** range query (e.g. col > ?) is assumed to match 1/4 of the rows in the
** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
** match 1/64 of the index. */
if( pLower && pUpper ) nNew -= 20;
nOut -= (pLower!=0) + (pUpper!=0);
if( nNew<10 ) nNew = 10;
if( nNew<nOut ) nOut = nNew;