1# 2020-02-23 2# 3# The author disclaims copyright to this source code. In place of 4# a legal notice, here is a blessing: 5# 6# May you do good and not evil. 7# May you find forgiveness for yourself and forgive others. 8# May you share freely, never taking more than you give. 9# 10#*********************************************************************** 11# Tests for functionality related to ANALYZE. 12# 13 14set testdir [file dirname $argv0] 15source $testdir/tester.tcl 16 17ifcapable !stat4 { 18 finish_test 19 return 20} 21set testprefix analyzeG 22 23proc do_scan_order_test {tn sql expect} { 24 uplevel [list do_test $tn [subst -nocommands { 25 set res "" 26 db eval "explain query plan $sql" { 27 lappend res [set detail] 28 } 29 set res 30 }] [list {*}$expect]] 31} 32 33#------------------------------------------------------------------------- 34# Test cases 1.* seek to verify that even if an index is not used, its 35# stat4 data may be used by the planner to estimate the number of 36# rows that match an unindexed constraint on the same column. 37# 38do_execsql_test 1.0 { 39 PRAGMA automatic_index = 0; 40 CREATE TABLE t1(a, x); 41 CREATE TABLE t2(b, y); 42 WITH s(i) AS ( 43 SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100 44 ) 45 INSERT INTO t1 SELECT (i%50), NULL FROM s; 46 WITH s(i) AS ( 47 SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100 48 ) 49 INSERT INTO t2 SELECT (CASE WHEN i<95 THEN 44 ELSE i END), NULL FROM s; 50} 51 52# Join tables t1 and t2. Both contain 100 rows. (a=44) matches 2 rows 53# in "t1", (b=44) matches 95 rows in table "t2". But the planner doesn't 54# know this, so it has no preference as to which order the tables are 55# scanned in. In practice this means that tables are scanned in the order 56# they are specified in in the FROM clause. 57do_scan_order_test 1.1.1 { 58 SELECT * FROM t1, t2 WHERE a=44 AND b=44; 59} { 60 {SCAN TABLE t1} {SCAN TABLE t2} 61} 62do_scan_order_test 1.1.2 { 63 SELECT * FROM t2, t1 WHERE a=44 AND b=44 64} { 65 {SCAN TABLE t2} {SCAN TABLE t1} 66} 67 68do_execsql_test 1.2 { 69 CREATE INDEX t2b ON t2(b); 70 ANALYZE; 71} 72 73# Now, with the ANALYZE data, the planner knows that (b=44) matches a 74# large number of rows. So it elects to scan table "t1" first, regardless 75# of the order in which the tables are specified in the FROM clause. 76do_scan_order_test 1.3.1 { 77 SELECT * FROM t1, t2 WHERE a=44 AND b=44; 78} { 79 {SCAN TABLE t1} {SCAN TABLE t2} 80} 81do_scan_order_test 1.3.2 { 82 SELECT * FROM t2, t1 WHERE a=44 AND b=44 83} { 84 {SCAN TABLE t1} {SCAN TABLE t2} 85} 86 87 88finish_test 89