SQLite

  if( j>=nTerm ){
    /* All terms of the ORDER BY clause are covered by this index so
    ** this index can be used for sorting. */
    return 1;
  }
  if( pIdx->onError!=OE_None && i==pIdx->nColumn
      && (wsFlags & WHERE_COLUMN_NULL)==0
      && !referencesOtherTables(pOrderBy, pMaskSet, j, base) 
  ){
    Column *aCol = pIdx->pTable->aCol;
    int i;

    /* All terms of this index match some prefix of the ORDER BY clause,
    ** the index is UNIQUE, and no terms on the tail of the ORDER BY
    ** refer to other tables in a join. So, assuming that the index entries
    ** visited contain no NULL values, then this index delivers rows in
    ** the required order.
    **
    ** It is not possible for any of the first nEqCol index fields to be
    ** NULL (since the corresponding "=" operator in the WHERE clause would 
    ** not be true). So if all remaining index columns have NOT NULL 
    ** constaints attached to them, we can be confident that the visited
    ** index entries are free of NULLs.  */
    for(i=nEqCol; i<pIdx->nColumn; i++){
      if( aCol[pIdx->aiColumn[i]].notNull==0 ) break;
    }
    return (i>=pIdx->nColumn);
  }
  return 0;
}

/*
** Prepare a crude estimate of the logarithm of the input value.
** The results need not be exact.  This is only used for estimating

# 2012 April 19
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# The tests in this file were used while developing the SQLite 4 code. 
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix tkt-2a5629202f

# This procedure executes the SQL.  Then it checks to see if the OP_Sort
# opcode was executed.  If an OP_Sort did occur, then "sort" is appended
# to the result.  If no OP_Sort happened, then "nosort" is appended.
#
# This procedure is used to check to make sure sorting is or is not
# occurring as expected.
#
proc cksort {sql} {
  set data [execsql $sql]
  if {[db status sort]} {set x sort} {set x nosort}
  lappend data $x
  return $data
}

do_execsql_test 1.1 {
  CREATE TABLE t8(b TEXT, c TEXT);
  INSERT INTO t8 VALUES('a',  'one');
  INSERT INTO t8 VALUES('b',  'two');
  INSERT INTO t8 VALUES(NULL, 'three');
  INSERT INTO t8 VALUES(NULL, 'four');
}

do_execsql_test 1.2 {
  SELECT coalesce(b, 'null') || '/' || c FROM t8 x ORDER BY x.b, x.c
} {null/four null/three a/one b/two}

do_execsql_test 1.3 {
  CREATE UNIQUE INDEX i1 ON t8(b);
  SELECT coalesce(b, 'null') || '/' || c FROM t8 x ORDER BY x.b, x.c
} {null/four null/three a/one b/two}

#-------------------------------------------------------------------------
#

do_execsql_test 2.1 {
  CREATE TABLE t2(a, b NOT NULL, c);
  CREATE UNIQUE INDEX t2ab ON t2(a, b);
  CREATE UNIQUE INDEX t2ba ON t2(b, a);
}

do_test 2.2 {
  cksort { SELECT * FROM t2 WHERE a = 10 ORDER BY a, b, c }
} {nosort}

do_test 2.3 {
  cksort { SELECT * FROM t2 WHERE b = 10 ORDER BY a, b, c }
} {sort}

do_test 2.4 {
  cksort { SELECT * FROM t2 WHERE a IS NULL ORDER BY a, b, c }
} {sort}

finish_test

} {1/1 1/4 4/1 4/4 nosort}
do_test where-14.4 {
  cksort {
    SELECT x.a || '/' || y.a FROM t8 x, t8 y ORDER BY x.a, x.b DESC
  } 
} {1/1 1/4 4/1 4/4 nosort}
do_test where-14.5 {
  # This test case changed from "nosort" to "sort". See ticket 2a5629202f.
  cksort {
    SELECT x.a || '/' || y.a FROM t8 x, t8 y ORDER BY x.b, x.a||x.b
  } 
} {4/1 4/4 1/1 1/4 sort}
do_test where-14.6 {
  # This test case changed from "nosort" to "sort". See ticket 2a5629202f.
  cksort {
    SELECT x.a || '/' || y.a FROM t8 x, t8 y ORDER BY x.b, x.a||x.b DESC
  } 
} {4/1 4/4 1/1 1/4 sort}
do_test where-14.7 {
  cksort {
    SELECT x.a || '/' || y.a FROM t8 x, t8 y ORDER BY x.b, y.a||y.b
  } 
} {4/1 4/4 1/1 1/4 sort}
do_test where-14.7.1 {
  cksort {