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Overview
Comment:Fix the query plan for an indexed lookup on a WITHOUT ROWID table with a DESC primary key when the primary key is constrained by an inequality. See forum post 8988341615. Test cases in TH3.
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SHA3-256: f65c929bf189cf5ca5f1cacdbbb8eec014c9960f767b135023bd2323cd26f279
User & Date: drh 2021-05-12 22:02:14
Context
2021-05-12
22:15
Further simplification of the reverse-order scan logic of the previous check-in. (check-in: b2b0e23b user: drh tags: trunk)
22:02
Fix the query plan for an indexed lookup on a WITHOUT ROWID table with a DESC primary key when the primary key is constrained by an inequality. See forum post 8988341615. Test cases in TH3. (check-in: f65c929b user: drh tags: trunk)
15:39
Fix a race condition that can lead to deadlock in the memdb VFS if one thread is trying to open an existing database at the same moment that another thread that is the only prior user of that database is trying to close it. (check-in: b635375d user: drh tags: trunk)
Changes
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Changes to src/wherecode.c.

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      pLevel->addrBignull = sqlite3VdbeMakeLabel(pParse);
    }

    /* If we are doing a reverse order scan on an ascending index, or
    ** a forward order scan on a descending index, interchange the 
    ** start and end terms (pRangeStart and pRangeEnd).
    */
    if( (nEq<pIdx->nKeyCol && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
     || (bRev && pIdx->nKeyCol==nEq)
    ){
      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
      SWAP(u8, bSeekPastNull, bStopAtNull);
      SWAP(u8, nBtm, nTop);
    }

    if( iLevel>0 && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 ){







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      pLevel->addrBignull = sqlite3VdbeMakeLabel(pParse);
    }

    /* If we are doing a reverse order scan on an ascending index, or
    ** a forward order scan on a descending index, interchange the 
    ** start and end terms (pRangeStart and pRangeEnd).
    */
    if( (nEq<pIdx->nColumn && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
     || (bRev && pIdx->nColumn==nEq)
    ){
      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
      SWAP(u8, bSeekPastNull, bStopAtNull);
      SWAP(u8, nBtm, nTop);
    }

    if( iLevel>0 && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 ){