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Overview
Comment:A better comment on the generated code for the NULL-in-RHS-of-IN detection logic.
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SHA1: 9bc1c730a366e75b760b58e7a343d39165b2a469
User & Date: drh 2014-08-01 21:12:35
Context
2014-08-02
20:44
Remove (newly) incorrect preprocessor check to fix build on WinRT. check-in: ba782654 user: mistachkin tags: trunk
2014-08-01
21:12
A better comment on the generated code for the NULL-in-RHS-of-IN detection logic. check-in: 9bc1c730 user: drh tags: trunk
21:00
Improved detection and handling of NULL values on the RHS of a IN operator. check-in: 468e7300 user: drh tags: trunk
Changes
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Changes to src/expr.c.

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*/
int sqlite3CodeOnce(Parse *pParse){
  Vdbe *v = sqlite3GetVdbe(pParse);      /* Virtual machine being coded */
  return sqlite3VdbeAddOp1(v, OP_Once, pParse->nOnce++);
}

/*
** Generate code that checks the single-column index table iCur to see if
** contains any NULL entries.  Cause the register at regHasNull to be set
** to a non-NULL value if iCur contains no NULLs.  Cause register regHasNull
** to be set to NULL if iCur contains one or more NULL values.
*/
static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
  int j1;
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regHasNull);
  j1 = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_Column, iCur, 0, regHasNull);
  sqlite3VdbeChangeP5(v, OPFLAG_TYPEOFARG);
  VdbeComment((v, "<maybe-NULL?>"));
  sqlite3VdbeJumpHere(v, j1);
}

/*
** This function is used by the implementation of the IN (...) operator.
** The pX parameter is the expression on the RHS of the IN operator, which
** might be either a list of expressions or a subquery.







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*/
int sqlite3CodeOnce(Parse *pParse){
  Vdbe *v = sqlite3GetVdbe(pParse);      /* Virtual machine being coded */
  return sqlite3VdbeAddOp1(v, OP_Once, pParse->nOnce++);
}

/*
** Generate code that checks the left-most column of index table iCur to see if
** it contains any NULL entries.  Cause the register at regHasNull to be set
** to a non-NULL value if iCur contains no NULLs.  Cause register regHasNull
** to be set to NULL if iCur contains one or more NULL values.
*/
static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
  int j1;
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regHasNull);
  j1 = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_Column, iCur, 0, regHasNull);
  sqlite3VdbeChangeP5(v, OPFLAG_TYPEOFARG);
  VdbeComment((v, "first_entry_in(%d)", iCur));
  sqlite3VdbeJumpHere(v, j1);
}

/*
** This function is used by the implementation of the IN (...) operator.
** The pX parameter is the expression on the RHS of the IN operator, which
** might be either a list of expressions or a subquery.