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Continuing refinements of the range-scan optimizations in where.c.

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The range scores are changed from an integer 1..9 to 0..100.

FossilOrigin-Name: f0c24b5fb86940f1a88adfb39cc4b9cbfcc66f8a
This commit is contained in:
drh
2009-08-20 18:14:42 +00:00
parent 68c4dbbdfc
commit 98cdf62690
4 changed files with 83 additions and 44 deletions
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89
src/where.c
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@@ -1900,9 +1900,10 @@ static void bestVirtualIndex(
** but smaller than the value of the second. And so on.
**
** If successful, this function determines which of the regions value
** pVal lies in, sets *piRegion to the region index and returns SQLITE_OK.
** pVal lies in, sets *piRegion to the region index (a value between 0
** and SQLITE_INDEX_SAMPLES+1, inclusive) and returns SQLITE_OK.
** Or, if an OOM occurs while converting text values between encodings,
** SQLITE_NOMEM is returned.
** SQLITE_NOMEM is returned and *piRegion is undefined.
*/
#ifdef SQLITE_ENABLE_STAT2
static int whereRangeRegion(
@@ -1991,7 +1992,7 @@ static int whereRangeRegion(
** | |
** pLower pUpper
**
** If the upper or lower bound is not present, then NULL should be passed in
** If either of the upper or lower bound is not present, then NULL is passed in
** place of the corresponding WhereTerm.
**
** The nEq parameter is passed the index of the index column subject to the
@@ -2008,12 +2009,17 @@ static int whereRangeRegion(
**
** then nEq should be passed 0.
**
** The returned value is an integer between 1 and 9, inclusive. A return
** The returned value is an integer between 1 and 100, inclusive. A return
** value of 1 indicates that the proposed range scan is expected to visit
** approximately 1/9 (11%) of the rows selected by the nEq equality constraints
** (if any). A return value of 9 indicates that it is expected that the
** range scan will visit 9/9 (100%) of the rows selected by the equality
** approximately 1/100th (1%) of the rows selected by the nEq equality
** constraints (if any). A return value of 100 indicates that it is expected
** that the range scan will visit every row (100%) selected by the equality
** constraints.
**
** In the absence of sqlite_stat2 ANALYZE data, each range inequality
** reduces the search space by 2/3rds. Hence a single constraint (x>?)
** results in a return of 33 and a range constraint (x>? AND x<?) results
** in a return of 11.
*/
static int whereRangeScanEst(
Parse *pParse, /* Parsing & code generating context */
@@ -2032,41 +2038,59 @@ static int whereRangeScanEst(
if( nEq==0 && p->aSample ){
int iEst;
int iUpper = SQLITE_INDEX_SAMPLES;
int iLower = 0;
int iUpper;
int iLower;
u8 aff = p->pTable->aCol[0].affinity;
if( pLower ){
Expr *pExpr = pLower->pExpr->pRight;
rc = sqlite3ValueFromExpr(db, pExpr, SQLITE_UTF8, aff, &pLowerVal);
if( !pLowerVal ) goto fallback;
}
if( pUpper ){
if( rc==SQLITE_OK && pUpper ){
Expr *pExpr = pUpper->pExpr->pRight;
rc = sqlite3ValueFromExpr(db, pExpr, SQLITE_UTF8, aff, &pUpperVal);
if( !pUpperVal ){
sqlite3ValueFree(pLowerVal);
goto fallback;
}
if( rc!=SQLITE_OK || (pLowerVal==0 && pUpperVal==0) ){
sqlite3ValueFree(pLowerVal);
sqlite3ValueFree(pUpperVal);
goto range_est_fallback;
}else if( pLowerVal==0 ){
rc = whereRangeRegion(pParse, p, pUpperVal, &iUpper);
iLower = pLower ? iUpper/2 : 0;
}else if( pUpperVal==0 ){
rc = whereRangeRegion(pParse, p, pLowerVal, &iLower);
iUpper = pUpper ? (iLower + SQLITE_INDEX_SAMPLES + 1)/2
: SQLITE_INDEX_SAMPLES;
}else{
rc = whereRangeRegion(pParse, p, pUpperVal, &iUpper);
if( rc==SQLITE_OK ){
rc = whereRangeRegion(pParse, p, pLowerVal, &iLower);
}else{
iLower = 0;
}
}
rc = whereRangeRegion(pParse, p, pUpperVal, &iUpper);
if( rc==SQLITE_OK ){
rc = whereRangeRegion(pParse, p, pLowerVal, &iLower);
}
iEst = iUpper - iLower;
if( iEst>=SQLITE_INDEX_SAMPLES ) iEst = SQLITE_INDEX_SAMPLES-1;
else if( iEst<1 ) iEst = 1;
if( iEst>SQLITE_INDEX_SAMPLES ){
iEst = SQLITE_INDEX_SAMPLES;
}else if( iEst<1 ){
iEst = 1;
}
sqlite3ValueFree(pLowerVal);
sqlite3ValueFree(pUpperVal);
*piEst = iEst;
*piEst = (iEst * 100)/SQLITE_INDEX_SAMPLES;
return rc;
}
fallback:
range_est_fallback:
#endif
assert( pLower || pUpper );
*piEst = (SQLITE_INDEX_SAMPLES-1) / ((pLower&&pUpper)?9:3);
if( pLower && pUpper ){
*piEst = 11;
}else{
*piEst = 33;
}
return rc;
}
@@ -2212,10 +2236,13 @@ static void bestBtreeIndex(
** in determining the value of nInMul.
**
** nBound:
** An estimate on the amount of the table that must be searched due
** to a range constraint. The value is between 1 and 9 and indicates
** 9ths of the table. 1 means that about 1/9th of the is searched.
** 9 indicates that the entire table is searched.
** An estimate on the amount of the table that must be searched. A
** value of 100 means the entire table is searched. Range constraints
** might reduce this to a value less than 100 to indicate that only
** a fraction of the table needs searching. In the absence of
** sqlite_stat2 ANALYZE data, a single inequality reduces the search
** space to 1/3rd its original size. So an x>? constraint reduces
** nBound to 33. Two constraints (x>? AND x<?) reduce nBound to 11.
**
** bSort:
** Boolean. True if there is an ORDER BY clause that will require an
@@ -2237,7 +2264,7 @@ static void bestBtreeIndex(
int nEq;
int bInEst = 0;
int nInMul = 1;
int nBound = 9;
int nBound = 100;
int bSort = 0;
int bLookup = 0;
@@ -2344,8 +2371,8 @@ static void bestBtreeIndex(
/* Adjust the number of rows and the cost downward to reflect rows
** that are excluded by range constraints.
*/
nRow = nRow * (double)nBound / (double)9;
cost = cost * (double)nBound / (double)9;
nRow = (nRow * (double)nBound) / (double)100;
cost = (cost * (double)nBound) / (double)100;
/* Add in the estimated cost of sorting the result
*/