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Overview
Comment:A few simple test cases for the ORDER BY LIMIT optimization.
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SHA1: 08849eab0f6ef29eaf6d2ce9c692de9b953dbd27
User & Date: drh 2016-05-20 00:21:42
Context
2016-05-20
13:44
Set the NULLEQ flag on the sequence counter comparison in the ORDER BY LIMIT optimization, to avoid coverage complaints about not testing the NULL case. Closed-Leaf check-in: ed1b30dc user: drh tags: orderby-limit
00:21
A few simple test cases for the ORDER BY LIMIT optimization. check-in: 08849eab user: drh tags: orderby-limit
2016-05-19
22:40
Appears to work now. Needs test cases, more comments, and code optimization. check-in: 990fe50c user: drh tags: orderby-limit
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Added test/limit2.test.





































































































































































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# 2016-05-20
#
# 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 file is testing the LIMIT in combination with ORDER BY
# and in particular, the optimizations in the inner loop that cause an
# early exit of the inner loop when the LIMIT is reached and the inner
# loop is emitting rows in ORDER BY order.


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

do_execsql_test limit2-100 {
  CREATE TABLE t1(a,b);
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<1000)
    INSERT INTO t1(a,b) SELECT 1, (x*17)%1000 + 1000 FROM c;
  INSERT INTO t1(a,b) VALUES(2,2),(3,1006),(4,4),(5,9999);
  CREATE INDEX t1ab ON t1(a,b);
}
set sqlite_search_count 0
do_execsql_test limit2-100.1 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
set fast_count $sqlite_search_count
set sqlite_search_count 0
do_execsql_test limit2-100.2 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY +b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
do_test limit2-100.3 {
  set slow_count $sqlite_search_count
  expr {$fast_count < 0.02*$slow_count}
} {1}

do_execsql_test limit2-110 {
  CREATE TABLE t2(x,y);
  INSERT INTO t2(x,y) VALUES('a',1),('a',2),('a',3),('a',4);
  INSERT INTO t2(x,y) VALUES('b',1),('c',2),('d',3),('e',4);
  CREATE INDEX t2xy ON t2(x,y);
}
set sqlite_search_count 0
do_execsql_test limit2-110.1 {
  SELECT a, b, '|' FROM t2, t1 WHERE t2.x='a' AND t1.a=t2.y ORDER BY t1.b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
set fast_count $sqlite_search_count
set sqlite_search_count 0
do_execsql_test limit2-110.2 {
  SELECT a, b, '|' FROM t2, t1 WHERE t2.x='a' AND t1.a=t2.y ORDER BY +t1.b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
set slow_count $sqlite_search_count
do_test limit2-110.3 {
  expr {$fast_count < 0.02*$slow_count}
} {1}

do_execsql_test limit2-120 {
  DROP INDEX t1ab;
  CREATE INDEX t1ab ON t1(a,b DESC);
}
set sqlite_search_count 0
do_execsql_test limit2-120.1 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY b DESC LIMIT 5;
} {5 9999 | 1 1999 | 1 1998 | 1 1997 | 1 1996 |}
set fast_count $sqlite_search_count
set sqlite_search_count 0
do_execsql_test limit2-120.2 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY +b DESC LIMIT 5;
} {5 9999 | 1 1999 | 1 1998 | 1 1997 | 1 1996 |}
do_test limit2-120.3 {
  set slow_count $sqlite_search_count
  expr {$fast_count < 0.02*$slow_count}
} {1}



finish_test