gitlab.com/CoiaPrant/sqlite3@v1.19.1/testdata/tcl/emptytable.test (about) 1 # 2017-02-15 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 # 12 # Test cases to show that a join involving an empty table is very fast. 13 # 14 15 set testdir [file dirname $argv0] 16 source $testdir/tester.tcl 17 18 # Build some test data 19 # 20 do_execsql_test emptytable-100 { 21 CREATE TABLE t1(a); 22 WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100) 23 INSERT INTO t1(a) SELECT x FROM c; 24 CREATE TABLE empty(x); 25 SELECT count(*) FROM t1; 26 } {100} 27 28 # Interrupt queries after 1M cycles to prevent burning excess CPU 29 proc stopDb {args} { 30 db interrupt 31 } 32 db progress 1000000 {stopDb} 33 34 # Prior to the query planner optimization on 2017-02-15, this query would 35 # take a ridiculous amount of time. If that optimization stops working, 36 # the result here will be in interrupt for running too long. 37 # 38 do_catchsql_test emptytable-110 { 39 SELECT count(*) FROM t1, t1, t1, t1, t1, t1, empty; 40 } {0 0} 41 42 do_catchsql_test emptytable-120 { 43 SELECT count(*) FROM t1, t1 LEFT JOIN empty; 44 } {0 10000} 45 do_catchsql_test emptytable-121 { 46 SELECT count(*) FROM t1, t1 LEFT JOIN t1, empty; 47 } {0 0} 48 49 50 finish_test