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