SQLite

    assert( p->rSetup==0 || pTemplate->rSetup==0 
                 || p->rSetup==pTemplate->rSetup );

    /* whereLoopAddBtree() always generates and inserts the automatic index
    ** case first.  Hence compatible candidate WhereLoops never have a larger
    ** rSetup. Call this SETUP-INVARIANT */
    assert( p->rSetup>=pTemplate->rSetup );

    /* Any loop using an appliation-defined index (or PRIMARY KEY or
    ** UNIQUE constraint) with one or more == constraints is better
    ** than an automatic index. */
    if( (p->wsFlags & WHERE_AUTO_INDEX)!=0
     && (pTemplate->wsFlags & WHERE_INDEXED)!=0
     && (pTemplate->wsFlags & WHERE_COLUMN_EQ)!=0
     && (p->prereq & pTemplate->prereq)==pTemplate->prereq
    ){
      break;
    }

    /* If existing WhereLoop p is better than pTemplate, pTemplate can be
    ** discarded.  WhereLoop p is better if:
    **   (1)  p has no more dependencies than pTemplate, and
    **   (2)  p has an equal or lower cost than pTemplate
    */
    if( (p->prereq & pTemplate->prereq)==p->prereq    /* (1)  */

    /* We will be overwriting WhereLoop p[].  But before we do, first
    ** go through the rest of the list and delete any other entries besides
    ** p[] that are also supplated by pTemplate */
    WhereLoop **ppTail = &p->pNextLoop;
    WhereLoop *pToDel;
    while( *ppTail ){
      ppTail = whereLoopFindLesser(ppTail, pTemplate);
      if( ppTail==0 ) break;
      pToDel = *ppTail;
      if( pToDel==0 ) break;
      *ppTail = pToDel->pNextLoop;
#if WHERETRACE_ENABLED /* 0x8 */
      if( sqlite3WhereTrace & 0x8 ){
        sqlite3DebugPrintf("ins-del: ");
        whereLoopPrint(pToDel, pBuilder->pWC);

# 2014-06-17
#
# 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.
#
#*************************************************************************
#
# This file implements regression tests for SQLite library.  The
# focus of this script is testing automatic index creation logic,
# and specifically that an automatic index will not be created that
# shadows a declared index.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# The t1b and t2d indexes are not very selective.  It used to be that
# the autoindex mechanism would create automatic indexes on t1(b) or
# t2(d), make assumptions that they were reasonably selective, and use
# them instead of t1b or t2d.  But that would be cheating, because the
# automatic index cannot be any more selective than the real index.
#
# This test verifies that the cheat is no longer allowed.
#
do_execsql_test autoindex3-100 {
  CREATE TABLE t1(a,b,x);
  CREATE TABLE t2(c,d,y);
  CREATE INDEX t1b ON t1(b);
  CREATE INDEX t2d ON t2(d);
  ANALYZE sqlite_master;
  INSERT INTO sqlite_stat1 VALUES('t1','t1b','10000 500');
  INSERT INTO sqlite_stat1 VALUES('t2','t2d','10000 500');
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1, t2 WHERE d=b;
} {~/AUTO/}

# Automatic indexes can still be used if existing indexes do not
# participate in == constraints.
#
do_execsql_test autoindex3-110 {
  EXPLAIN QUERY PLAN SELECT * FROM t1, t2 WHERE d>b AND x=y;
} {/AUTO/}
do_execsql_test autoindex3-120 {
  EXPLAIN QUERY PLAN SELECT * FROM t1, t2 WHERE d<b AND x=y;
} {/AUTO/}
do_execsql_test autoindex3-130 {
  EXPLAIN QUERY PLAN SELECT * FROM t1, t2 WHERE d IS NULL AND x=y;
} {/AUTO/}
do_execsql_test autoindex3-140 {
  EXPLAIN QUERY PLAN SELECT * FROM t1, t2 WHERE d IN (5,b) AND x=y;
} {/AUTO/}


finish_test