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Enhance the generate_series() table-valued function to support negative

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step values.

FossilOrigin-Name: 9b60fc48706bb77b2d4fe27a7b5834a6dc229b4051a9285032da578e4f2849e6
This commit is contained in:
drh
2020-12-03 14:21:26 +00:00
parent 4338000d47
commit 0b1e70c4ce
3 changed files with 21 additions and 11 deletions
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16
ext/misc/series.c
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@ -247,7 +247,8 @@ static int seriesEof(sqlite3_vtab_cursor *cur){
** 4: step=VALUE
**
** Also, if bit 8 is set, that means that the series should be output
** in descending order rather than in ascending order.
** in descending order rather than in ascending order. If bit 16 is
** set, then output must appear in ascending order.
**
** This routine should initialize the cursor and position it so that it
** is pointing at the first row, or pointing off the end of the table
@ -273,7 +274,12 @@ static int seriesFilter(
}
if( idxNum & 4 ){
pCur->iStep = sqlite3_value_int64(argv[i++]);
if( pCur->iStep<1 ) pCur->iStep = 1;
if( pCur->iStep==0 ){
pCur->iStep = 1;
}else if( pCur->iStep<0 ){
pCur->iStep = -pCur->iStep;
if( (idxNum & 16)==0 ) idxNum |= 8;
}
}else{
pCur->iStep = 1;
}
@ -367,7 +373,11 @@ static int seriesBestIndex(
pIdxInfo->estimatedCost = (double)(2 - ((idxNum&4)!=0));
pIdxInfo->estimatedRows = 1000;
if( pIdxInfo->nOrderBy==1 ){
if( pIdxInfo->aOrderBy[0].desc ) idxNum |= 8;
if( pIdxInfo->aOrderBy[0].desc ){
idxNum |= 8;
}else{
idxNum |= 16;
}
pIdxInfo->orderByConsumed = 1;
}
}else{