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Overview
Comment:Corrections to comments on the whereScanInit() interface.
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SHA1: ab7ab415d19524f6c3901e474d3a154f55d28530
User & Date: drh 2016-05-06 18:47:23
Context
2016-05-06
20:23
Simplification to the logic used to decide between OP_Seek and OP_NotExists. Use OP_NotExists for both DELETE and UPDATE. check-in: 3a695263 user: drh tags: trunk
18:47
Corrections to comments on the whereScanInit() interface. check-in: ab7ab415 user: drh tags: trunk
16:49
For DELETE operations, make sure that seeks on the main table are not deferred, since if they are and none of the indexes reference columns of the table, the seek might never occur until the OP_Delete opcode, which is too late. Fix for ticket [16c9801ceba49]. check-in: 93a2bace user: drh tags: trunk
Changes
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Changes to src/where.c.

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/*
** Initialize a WHERE clause scanner object.  Return a pointer to the
** first match.  Return NULL if there are no matches.
**
** The scanner will be searching the WHERE clause pWC.  It will look
** for terms of the form "X <op> <expr>" where X is column iColumn of table



** iCur.  The <op> must be one of the operators described by opMask.
**
** If the search is for X and the WHERE clause contains terms of the
** form X=Y then this routine might also return terms of the form
** "Y <op> <expr>".  The number of levels of transitivity is limited,
** but is enough to handle most commonly occurring SQL statements.
**
** If X is not the INTEGER PRIMARY KEY then X must be compatible with
................................................................................
  pScan->nEquiv = 1;
  pScan->iEquiv = 1;
  return whereScanNext(pScan);
}

/*
** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
** where X is a reference to the iColumn of table iCur and <op> is one of
** the WO_xx operator codes specified by the op parameter.
** Return a pointer to the term.  Return 0 if not found.
**

** If pIdx!=0 then search for terms matching the iColumn-th column of pIdx
** rather than the iColumn-th column of table iCur.
**
** The term returned might by Y=<expr> if there is another constraint in
** the WHERE clause that specifies that X=Y.  Any such constraints will be
** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
** aiCur[]/iaColumn[] arrays hold X and all its equivalents. There are 11
** slots in aiCur[]/aiColumn[] so that means we can look for X plus up to 10







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/*
** Initialize a WHERE clause scanner object.  Return a pointer to the
** first match.  Return NULL if there are no matches.
**
** The scanner will be searching the WHERE clause pWC.  It will look
** for terms of the form "X <op> <expr>" where X is column iColumn of table
** iCur.   Or if pIdx!=0 then X is column iColumn of index pIdx.  pIdx
** must be one of the indexes of table iCur.
**
** The <op> must be one of the operators described by opMask.
**
** If the search is for X and the WHERE clause contains terms of the
** form X=Y then this routine might also return terms of the form
** "Y <op> <expr>".  The number of levels of transitivity is limited,
** but is enough to handle most commonly occurring SQL statements.
**
** If X is not the INTEGER PRIMARY KEY then X must be compatible with
................................................................................
  pScan->nEquiv = 1;
  pScan->iEquiv = 1;
  return whereScanNext(pScan);
}

/*
** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
** where X is a reference to the iColumn of table iCur or of index pIdx
** if pIdx!=0 and <op> is one of the WO_xx operator codes specified by
** the op parameter.  Return a pointer to the term.  Return 0 if not found.
**
** If pIdx!=0 then it must be one of the indexes of table iCur.  
** Search for terms matching the iColumn-th column of pIdx
** rather than the iColumn-th column of table iCur.
**
** The term returned might by Y=<expr> if there is another constraint in
** the WHERE clause that specifies that X=Y.  Any such constraints will be
** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
** aiCur[]/iaColumn[] arrays hold X and all its equivalents. There are 11
** slots in aiCur[]/aiColumn[] so that means we can look for X plus up to 10