github.com/jdgcs/sqlite3@v1.12.1-0.20210908114423-bc5f96e4dd51/testdata/tcl/analyzeG.test (about)

     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  
    14  set testdir [file dirname $argv0]
    15  source $testdir/tester.tcl
    16  
    17  ifcapable !stat4 {
    18    finish_test
    19    return
    20  }
    21  set testprefix analyzeG
    22  
    23  #-------------------------------------------------------------------------
    24  # Test cases 1.* seek to verify that even if an index is not used, its
    25  # stat4 data may be used by the planner to estimate the number of
    26  # rows that match an unindexed constraint on the same column.
    27  #
    28  do_execsql_test 1.0 {
    29    PRAGMA automatic_index = 0;
    30    CREATE TABLE t1(a, x);
    31    CREATE TABLE t2(b, y);
    32    WITH s(i) AS (
    33      SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100
    34    )
    35    INSERT INTO t1 SELECT (i%50), NULL FROM s;
    36    WITH s(i) AS (
    37      SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100
    38    )
    39    INSERT INTO t2 SELECT (CASE WHEN i<95 THEN 44 ELSE i END), NULL FROM s;
    40  }
    41  
    42  # Join tables t1 and t2. Both contain 100 rows. (a=44) matches 2 rows
    43  # in "t1", (b=44) matches 95 rows in table "t2". But the planner doesn't
    44  # know this, so it has no preference as to which order the tables are
    45  # scanned in. In practice this means that tables are scanned in the order
    46  # they are specified in in the FROM clause.
    47  do_eqp_test 1.1.1 {
    48    SELECT * FROM t1, t2 WHERE a=44 AND b=44;
    49  } {
    50  
    51  }
    52  do_eqp_test 1.1.2 {
    53    SELECT * FROM t2, t1 WHERE a=44 AND b=44 
    54  } {
    55    QUERY PLAN
    56    |--SCAN t2
    57    `--SCAN t1
    58  }
    59  
    60  do_execsql_test 1.2 {
    61    CREATE INDEX t2b ON t2(b);
    62    ANALYZE;
    63  }
    64  
    65  # Now, with the ANALYZE data, the planner knows that (b=44) matches a 
    66  # large number of rows. So it elects to scan table "t1" first, regardless
    67  # of the order in which the tables are specified in the FROM clause.
    68  do_eqp_test 1.3.1 {
    69    SELECT * FROM t1, t2 WHERE a=44 AND b=44;
    70  } {
    71    QUERY PLAN
    72    |--SCAN t1
    73    `--SCAN t2
    74  }
    75  do_eqp_test 1.3.2 {
    76    SELECT * FROM t2, t1 WHERE a=44 AND b=44 
    77  } {
    78    QUERY PLAN
    79    |--SCAN t1
    80    `--SCAN t2
    81  }
    82  
    83  
    84  finish_test