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61 lines
1.8 KiB
Plaintext
61 lines
1.8 KiB
Plaintext
# 2016-07-27
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#
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# The author disclaims copyright to this source code. In place of
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# a legal notice, here is a blessing:
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#
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# May you do good and not evil.
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# May you find forgiveness for yourself and forgive others.
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# May you share freely, never taking more than you give.
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#
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#***********************************************************************
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#
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# Test cases for ORDER BY and LIMIT on an index scan.
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#
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set testdir [file dirname $argv0]
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source $testdir/tester.tcl
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# Performance regression reported at
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# http://www.mail-archive.com/sqlite-users@mailinglists.sqlite.org/msg98615.html
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#
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# Caused by the ORDER BY LIMIT optionation for check-in
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# https://sqlite.org/src/info/bf46179d44843769
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#
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# Fixed on approximately 2016-07-27 by changes that compute a better score
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# for index scans by taking into account WHERE clause constraints that can
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# be handled by the index and do not require a table lookup.
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#
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do_execsql_test 1.0 {
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CREATE TABLE t1(a,b,c,d);
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WITH RECURSIVE c(x) AS (VALUES(0) UNION ALL SELECT x+1 FROM c WHERE x<100)
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INSERT INTO t1(a,b,c,d)
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SELECT x/10, x%10, x%19, x FROM c;
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CREATE INDEX t1abc ON t1(a,b,c);
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SELECT * FROM t1 WHERE c=4 ORDER BY a, b LIMIT 2;
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} {0 4 4 4 2 3 4 23}
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# Prior to the fix, the following EQP would show a table scan and a sort
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# rather than an index scan.
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#
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do_execsql_test 1.0eqp {
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EXPLAIN QUERY PLAN
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SELECT * FROM t1 WHERE c=4 ORDER BY a, b LIMIT 2;
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} {/SCAN t1 USING INDEX t1abc/}
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# If we change the index so that it no longer covers the WHERE clause,
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# then we should (correctly) revert to using a table scan.
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#
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do_execsql_test 1.1 {
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DROP INDEX t1abc;
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CREATE INDEX t1abd ON t1(a,b,d);
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SELECT * FROM t1 WHERE c=4 ORDER BY a, b LIMIT 2;
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} {0 4 4 4 2 3 4 23}
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do_execsql_test 1.1eqp {
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EXPLAIN QUERY PLAN
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SELECT * FROM t1 WHERE c=4 ORDER BY a, b LIMIT 2;
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} {~/USING INDEX/}
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finish_test
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