sqlite/test/analyzeG.test

# 2020-02-23
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# Tests for functionality related to ANALYZE.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable !stat4 {
  finish_test
  return
}
set testprefix analyzeG

#-------------------------------------------------------------------------
# Test cases 1.* seek to verify that even if an index is not used, its
# stat4 data may be used by the planner to estimate the number of
# rows that match an unindexed constraint on the same column.
#
do_execsql_test 1.0 {
  PRAGMA automatic_index = 0;
  CREATE TABLE t1(a, x);
  CREATE TABLE t2(b, y);
  WITH s(i) AS (
    SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100
  )
  INSERT INTO t1 SELECT (i%50), NULL FROM s;
  WITH s(i) AS (
    SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<100
  )
  INSERT INTO t2 SELECT (CASE WHEN i<95 THEN 44 ELSE i END), NULL FROM s;
}

# Join tables t1 and t2. Both contain 100 rows. (a=44) matches 2 rows
# in "t1", (b=44) matches 95 rows in table "t2". But the planner doesn't
# know this, so it has no preference as to which order the tables are
# scanned in. In practice this means that tables are scanned in the order
# they are specified in in the FROM clause.
do_eqp_test 1.1.1 {
  SELECT * FROM t1, t2 WHERE a=44 AND b=44;
} {

}
do_eqp_test 1.1.2 {
  SELECT * FROM t2, t1 WHERE a=44 AND b=44 
} {
  QUERY PLAN
  |--SCAN t2
  `--SCAN t1
}

do_execsql_test 1.2 {
  CREATE INDEX t2b ON t2(b);
  ANALYZE;
}

# Now, with the ANALYZE data, the planner knows that (b=44) matches a 
# large number of rows. So it elects to scan table "t1" first, regardless
# of the order in which the tables are specified in the FROM clause.
do_eqp_test 1.3.1 {
  SELECT * FROM t1, t2 WHERE a=44 AND b=44;
} {
  QUERY PLAN
  |--SCAN t1
  `--SCAN t2
}
do_eqp_test 1.3.2 {
  SELECT * FROM t2, t1 WHERE a=44 AND b=44 
} {
  QUERY PLAN
  |--SCAN t1
  `--SCAN t2
}


finish_test