mirror of https://github.com/sqlite/sqlite
89 lines
2.4 KiB
Plaintext
89 lines
2.4 KiB
Plaintext
# 2020-02-23
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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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# Tests for functionality related to ANALYZE.
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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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ifcapable !stat4 {
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finish_test
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return
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}
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set testprefix analyzeG
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proc do_scan_order_test {tn sql expect} {
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uplevel [list do_test $tn [subst -nocommands {
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set res ""
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db eval "explain query plan $sql" {
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lappend res [set detail]
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}
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set res
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}] [list {*}$expect]]
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}
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#-------------------------------------------------------------------------
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# Test cases 1.* seek to verify that even if an index is not used, its
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# stat4 data may be used by the planner to estimate the number of
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# rows that match an unindexed constraint on the same column.
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#
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do_execsql_test 1.0 {
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PRAGMA automatic_index = 0;
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CREATE TABLE t1(a, x);
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CREATE TABLE t2(b, y);
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WITH s(i) AS (
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SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100
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)
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INSERT INTO t1 SELECT (i%50), NULL FROM s;
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WITH s(i) AS (
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SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100
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)
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INSERT INTO t2 SELECT (CASE WHEN i<95 THEN 44 ELSE i END), NULL FROM s;
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}
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# Join tables t1 and t2. Both contain 100 rows. (a=44) matches 2 rows
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# in "t1", (b=44) matches 95 rows in table "t2". But the planner doesn't
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# know this, so it has no preference as to which order the tables are
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# scanned in. In practice this means that tables are scanned in the order
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# they are specified in in the FROM clause.
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do_scan_order_test 1.1.1 {
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SELECT * FROM t1, t2 WHERE a=44 AND b=44;
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} {
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{SCAN TABLE t1} {SCAN TABLE t2}
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}
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do_scan_order_test 1.1.2 {
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SELECT * FROM t2, t1 WHERE a=44 AND b=44
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} {
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{SCAN TABLE t2} {SCAN TABLE t1}
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}
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do_execsql_test 1.2 {
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CREATE INDEX t2b ON t2(b);
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ANALYZE;
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}
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# Now, with the ANALYZE data, the planner knows that (b=44) matches a
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# large number of rows. So it elects to scan table "t1" first, regardless
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# of the order in which the tables are specified in the FROM clause.
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do_scan_order_test 1.3.1 {
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SELECT * FROM t1, t2 WHERE a=44 AND b=44;
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} {
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{SCAN TABLE t1} {SCAN TABLE t2}
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}
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do_scan_order_test 1.3.2 {
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SELECT * FROM t2, t1 WHERE a=44 AND b=44
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} {
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{SCAN TABLE t1} {SCAN TABLE t2}
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}
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finish_test
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