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Overview
Comment:Do a more thorough job of cleaning traces of the strength-reduced LEFT JOIN.
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Timelines: family | ancestors | descendants | both | join-strength-reduction
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SHA3-256: 08833dda3a25965cc509d0244d7cd68bdb2306351ca52862f347e1efe5db4508
User & Date: drh 2018-03-20 22:52:27.787
Original Comment: Do a more thorough job of cleaning erasing traces of the strength-reduced LEFT JOIN.
Context
2018-03-21
01:59
Relax LEFT-JOIN restrictions on the push-down optimization. (Closed-Leaf check-in: b5d3dd8cb0 user: drh tags: join-strength-reduction)
2018-03-20
22:52
Do a more thorough job of cleaning traces of the strength-reduced LEFT JOIN. (check-in: 08833dda3a user: drh tags: join-strength-reduction)
21:16
If terms of the WHERE clause require that the right table in a LEFT JOIN not be a null row, then simplify the LEFT JOIN into an ordinary JOIN. (check-in: 5b7abecc7a user: drh tags: join-strength-reduction)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/select.c.
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    */
    if( (pItem->fg.jointype & JT_LEFT)!=0
     && sqlite3ExprImpliesNonNullRow(p->pWhere, pItem->iCursor)
     && OptimizationEnabled(db, SQLITE_SimplifyJoin)
    ){
      SELECTTRACE(0x100,pParse,p,
                ("LEFT-JOIN simplifies to JOIN on term %d\n",i));
      pItem->fg.jointype &= ~JT_LEFT;
      unsetJoinExpr(p->pWhere, pItem->iCursor);
    }

    /* No futher action if this term of the FROM clause is no a subquery */
    if( pSub==0 ) continue;

    /* Catch mismatch in the declared columns of a view and the number of








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    */
    if( (pItem->fg.jointype & JT_LEFT)!=0
     && sqlite3ExprImpliesNonNullRow(p->pWhere, pItem->iCursor)
     && OptimizationEnabled(db, SQLITE_SimplifyJoin)
    ){
      SELECTTRACE(0x100,pParse,p,
                ("LEFT-JOIN simplifies to JOIN on term %d\n",i));
      pItem->fg.jointype &= ~(JT_LEFT|JT_OUTER);
      unsetJoinExpr(p->pWhere, pItem->iCursor);
    }

    /* No futher action if this term of the FROM clause is no a subquery */
    if( pSub==0 ) continue;

    /* Catch mismatch in the declared columns of a view and the number of
︙︙
Changes to test/cursorhint2.test.
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do_extract_hints_test 2.5 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 1 = coalesce(b, 1)
} {
  x2 {EQ(c0,r[2])}
}




do_extract_hints_test 2.6 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 0 = (b IS NOT NULL)
} {
  x2 {EQ(c0,r[2])}
}

do_extract_hints_test 2.7 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 0 = (b IS NOT +NULL)
} {
  x2 {EQ(c0,r[2])}
}

do_extract_hints_test 2.8 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE b IS NOT +NULL
} {
  x2 {EQ(c0,r[2])}
}

do_extract_hints_test 2.9 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE CASE b WHEN 0 THEN 0 ELSE 1 END;

} {
  x2 {EQ(c0,r[2])}
}

do_extract_hints_test 2.10 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b = 32+32
} {
  x2 {AND(EQ(c1,ADD(32,32)),EQ(c0,r[2]))}
}

ifcapable !icu {
  # This test only works using the built-in LIKE, not the ICU LIKE extension.
  do_extract_hints_test 2.11 {
    SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b LIKE 'abc%'
  } {
    x2 {AND(expr,EQ(c0,r[2]))}
  }
}


do_extract_hints_test 2.12 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE coalesce(x2.b, 1)
} {
  x2 {EQ(c0,r[2])}
}

finish_test








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do_extract_hints_test 2.5 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 1 = coalesce(b, 1)
} {
  x2 {EQ(c0,r[2])}
}

if {0} {
  # These tests no longer work due to the LEFT-JOIN strength reduction
  # optimization
  do_extract_hints_test 2.6 {
    SELECT * FROM x1 CROSS JOIN x2 ON (a=x) WHERE 0 = (b IS NOT NULL)
  } {
    x2 {EQ(c0,r[2])}
  }
  
  do_extract_hints_test 2.7 {
    SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 0 = (b IS NOT +NULL)
  } {
    x2 {EQ(c0,r[2])}
  }
  
  do_extract_hints_test 2.8 {
    SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE b IS NOT +NULL
  } {
    x2 {EQ(c0,r[2])}
  }
  
  do_extract_hints_test 2.9 {
    SELECT * FROM x1 LEFT JOIN x2 ON (a=x)
      WHERE CASE b WHEN 0 THEN 0 ELSE 1 END;
  } {
    x2 {EQ(c0,r[2])}
  }
  
  do_extract_hints_test 2.10 {
    SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b = 32+32
  } {
    x2 {AND(EQ(c1,ADD(32,32)),EQ(c0,r[2]))}
  }
  
  ifcapable !icu {
    # This test only works using the built-in LIKE, not the ICU LIKE extension.
    do_extract_hints_test 2.11 {
      SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b LIKE 'abc%'
    } {
      x2 {AND(expr,EQ(c0,r[2]))}
    }
  }
}
  
do_extract_hints_test 2.12 {
  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE coalesce(x2.b, 1)
} {
  x2 {EQ(c0,r[2])}
}

finish_test