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Overview
Comment:Improvements to the LEFT JOIN strength reduction optimization.
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SHA3-256: 548082dfab5d9484279ccc11cd2833ac131b54b7481372b576d7c28bbb3294ea
User & Date: drh 2019-10-11 16:01:21
Context
2019-10-11
17:14
Futher improvements to LEFT JOIN strength reduction. check-in: 8a39167bd2 user: drh tags: trunk
16:01
Improvements to the LEFT JOIN strength reduction optimization. check-in: 548082dfab user: drh tags: trunk
15:33
Ensure fts3/4 prefix indexes are flushed to disk before an 'optimize' command. Fix for [745f1abc]. check-in: 4ed905b188 user: dan tags: trunk
Changes
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Changes to src/expr.c.

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** clause requires that some column of the right table of the LEFT JOIN
** be non-NULL, then the LEFT JOIN can be safely converted into an
** ordinary join.
*/
int sqlite3ExprImpliesNonNullRow(Expr *p, int iTab){
  Walker w;
  p = sqlite3ExprSkipCollateAndLikely(p);

  if( p && p->op==TK_NOTNULL ){
    p = p->pLeft;



  }
  w.xExprCallback = impliesNotNullRow;
  w.xSelectCallback = 0;
  w.xSelectCallback2 = 0;
  w.eCode = 0;
  w.u.iCur = iTab;
  sqlite3WalkExpr(&w, p);







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** clause requires that some column of the right table of the LEFT JOIN
** be non-NULL, then the LEFT JOIN can be safely converted into an
** ordinary join.
*/
int sqlite3ExprImpliesNonNullRow(Expr *p, int iTab){
  Walker w;
  p = sqlite3ExprSkipCollateAndLikely(p);
  if( p==0 ) return 0;
  if( p->op==TK_NOTNULL ){
    p = p->pLeft;
  }else if( p->op==TK_AND ){
    if( sqlite3ExprImpliesNonNullRow(p->pLeft, iTab) ) return 1;
    p = p->pRight;
  }
  w.xExprCallback = impliesNotNullRow;
  w.xSelectCallback = 0;
  w.xSelectCallback2 = 0;
  w.eCode = 0;
  w.u.iCur = iTab;
  sqlite3WalkExpr(&w, p);