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Overview
Comment:Ensure that the query planner knows that any column of a flattened LEFT JOIN can be NULL even if that column is labeled with "NOT NULL". Fix for ticket [892fc34f173e99d8].
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SHA3-256:483462682d3a57fb9dd85b4772596e9738f1694a454b8ebbc480b9452733e88d
User & Date: dan 2017-06-20 17:43:26
Context
2017-06-20
18:19
Rename the azCompileOpt global constant to avoid a harmless compiler warning about a name conflict with a local variable. check-in: 94e420ec user: drh tags: trunk
17:43
Ensure that the query planner knows that any column of a flattened LEFT JOIN can be NULL even if that column is labeled with "NOT NULL". Fix for ticket [892fc34f173e99d8]. check-in: 48346268 user: dan tags: trunk
2017-06-17
18:49
Fix a missing comma in the previous check-in. check-in: f3db02f4 user: drh tags: trunk
Changes
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Changes to src/select.c.

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          memset(&ifNullRow, 0, sizeof(ifNullRow));
          ifNullRow.op = TK_IF_NULL_ROW;
          ifNullRow.pLeft = pCopy;
          ifNullRow.iTable = pSubst->iNewTable;
          pCopy = &ifNullRow;
        }
        pNew = sqlite3ExprDup(db, pCopy, 0);
        if( pNew && (pExpr->flags & EP_FromJoin) ){



          pNew->iRightJoinTable = pExpr->iRightJoinTable;
          pNew->flags |= EP_FromJoin;
        }
        sqlite3ExprDelete(db, pExpr);
        pExpr = pNew;
      }
    }
  }else{
    if( pExpr->op==TK_IF_NULL_ROW && pExpr->iTable==pSubst->iTable ){
................................................................................
  **
  **         (t1 LEFT OUTER JOIN t2) JOIN t3
  **
  ** which is not at all the same thing.
  **
  ** If the subquery is the right operand of a LEFT JOIN, then the outer
  ** query cannot be an aggregate.  This is an artifact of the way aggregates
  ** are processed - there is not mechanism to determine if the LEFT JOIN
  ** table should be all-NULL.
  **
  ** See also tickets #306, #350, and #3300.
  */
  if( (pSubitem->fg.jointype & JT_OUTER)!=0 ){
    isLeftJoin = 1;
    if( pSubSrc->nSrc>1 || isAgg ){







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          memset(&ifNullRow, 0, sizeof(ifNullRow));
          ifNullRow.op = TK_IF_NULL_ROW;
          ifNullRow.pLeft = pCopy;
          ifNullRow.iTable = pSubst->iNewTable;
          pCopy = &ifNullRow;
        }
        pNew = sqlite3ExprDup(db, pCopy, 0);
        if( pNew && pSubst->isLeftJoin ){
          ExprSetProperty(pNew, EP_CanBeNull);
        }
        if( pNew && ExprHasProperty(pExpr,EP_FromJoin) ){
          pNew->iRightJoinTable = pExpr->iRightJoinTable;
          ExprSetProperty(pNew, EP_FromJoin);
        }
        sqlite3ExprDelete(db, pExpr);
        pExpr = pNew;
      }
    }
  }else{
    if( pExpr->op==TK_IF_NULL_ROW && pExpr->iTable==pSubst->iTable ){
................................................................................
  **
  **         (t1 LEFT OUTER JOIN t2) JOIN t3
  **
  ** which is not at all the same thing.
  **
  ** If the subquery is the right operand of a LEFT JOIN, then the outer
  ** query cannot be an aggregate.  This is an artifact of the way aggregates
  ** are processed - there is no mechanism to determine if the LEFT JOIN
  ** table should be all-NULL.
  **
  ** See also tickets #306, #350, and #3300.
  */
  if( (pSubitem->fg.jointype & JT_OUTER)!=0 ){
    isLeftJoin = 1;
    if( pSubSrc->nSrc>1 || isAgg ){

Changes to test/join.test.

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} {2 2 1 |}
do_execsql_test join-14.11 {
  SELECT *, '|' FROM t3 LEFT JOIN v2 ON a=x WHERE b+1=x;
} {2 2 1 |}
do_execsql_test join-14.12 {
  SELECT *, '|' FROM t3 LEFT JOIN v2 ON a=x ORDER BY b;
} {4 {} {} | 2 2 1 |}


















finish_test








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} {2 2 1 |}
do_execsql_test join-14.11 {
  SELECT *, '|' FROM t3 LEFT JOIN v2 ON a=x WHERE b+1=x;
} {2 2 1 |}
do_execsql_test join-14.12 {
  SELECT *, '|' FROM t3 LEFT JOIN v2 ON a=x ORDER BY b;
} {4 {} {} | 2 2 1 |}

# Verify the fix for ticket
# https://www.sqlite.org/src/info/892fc34f173e99d8
#
db close
sqlite3 db :memory:
do_execsql_test join-14.20 {
  CREATE TABLE t1(id INTEGER PRIMARY KEY);
  CREATE TABLE t2(id INTEGER PRIMARY KEY, c2 INTEGER);
  CREATE TABLE t3(id INTEGER PRIMARY KEY, c3 INTEGER);
  INSERT INTO t1(id) VALUES(456);
  INSERT INTO t3(id) VALUES(1),(2);
  SELECT t1.id, x2.id, x3.id
  FROM t1
  LEFT JOIN (SELECT * FROM t2) AS x2 ON t1.id=x2.c2
  LEFT JOIN t3 AS x3 ON x2.id=x3.c3;
} {456 {} {}}

finish_test