SQLite

        k = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[j]);
        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
      }
      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
    }

    if( pLevel->iLeftJoin==0 ){
      /* If pIdx is an index on one or more expressions, then look through
      ** all the expressions in pWInfo and try to transform matching expressions
      ** into reference to index columns.  Also attempt to translate references
      ** to virtual columns in the table into references to (stored) columns
      ** of the index.
      **
      ** Do not do this for the RHS of a LEFT JOIN. This is because the 
      ** expression may be evaluated after OP_NullRow has been executed on
      ** the cursor. In this case it is important to do the full evaluation,
      ** as the result of the expression may not be NULL, even if all table
      ** column values are.  https://www.sqlite.org/src/info/7fa8049685b50b5a
      **
      ** Also, do not do this when processing one index an a multi-index
      ** OR clause, since the transformation will become invalid once we
      ** move forward to the next index.
      ** https://sqlite.org/src/info/4e8e4857d32d401f
      */
      if( (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0 ){
        whereIndexExprTrans(pIdx, iCur, iIdxCur, pWInfo);
      }
  
      /* If a partial index is driving the loop, try to eliminate WHERE clause
      ** terms from the query that must be true due to the WHERE clause of
      ** the partial index.
      **
      ** 2019-11-02 ticket 623eff57e76d45f6: This optimization does not work
      ** for a LEFT JOIN.
      */
      if( pIdx->pPartIdxWhere ){
        whereApplyPartialIndexConstraints(pIdx->pPartIdxWhere, iCur, pWC);
      }
    }else{
      testcase( (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0 );
      testcase( pIdx->pPartIdxWhere );
    }
  
    /* Record the instruction used to terminate the loop. */
    if( pLoop->wsFlags & WHERE_ONEROW ){
      pLevel->op = OP_Noop;
    }else if( bRev ){
      pLevel->op = OP_Prev;
    }else{
      pLevel->op = OP_Next;

  SELECT (b IS NOT NULL) IS NOT NULL FROM t1 LEFT JOIN t2
} {1}

do_execsql_test join-19.5 {
  SELECT * FROM t1 LEFT JOIN t2 WHERE 
    (b IS NOT NULL AND b IS NOT NULL) IS NOT NULL; 
} {0 {}}

# 2019-11-02 ticket 623eff57e76d45f6
# The optimization of exclusing the WHERE expression of a partial index
# from the WHERE clause of the query if the index is used does not work
# of the table of the index is the right-hand table of a LEFT JOIN.
#
db close
sqlite3 db :memory:
do_execsql_test join-20.1 {
  CREATE TABLE t1(c1);
  CREATE TABLE t0(c0);
  INSERT INTO t0(c0) VALUES (0);
  SELECT * FROM t0 LEFT JOIN t1 WHERE NULL IN (c1);
} {}
do_execsql_test join-20.2 {
  CREATE INDEX t1x ON t1(0) WHERE NULL IN (c1);
  SELECT * FROM t0 LEFT JOIN t1 WHERE NULL IN (c1);
} {}

finish_test