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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Artifact 3ea1cccca8f1b0e1cf3e73a63b43dd796f34d4aaee815e641f0d2ebb3fa448d4:


# 2013-11-13
#
# 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.
#
#***********************************************************************
#
# This file implements tests of the "skip-scan" query strategy.
#

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

do_execsql_test skipscan1-1.1 {
  CREATE TABLE t1(a TEXT, b INT, c INT, d INT);
  CREATE INDEX t1abc ON t1(a,b,c);
  INSERT INTO t1 VALUES('abc',123,4,5);
  INSERT INTO t1 VALUES('abc',234,5,6);
  INSERT INTO t1 VALUES('abc',234,6,7);
  INSERT INTO t1 VALUES('abc',345,7,8);
  INSERT INTO t1 VALUES('def',567,8,9);
  INSERT INTO t1 VALUES('def',345,9,10);
  INSERT INTO t1 VALUES('bcd',100,6,11);

  /* Fake the sqlite_stat1 table so that the query planner believes
  ** the table contains thousands of rows and that the first few
  ** columns are not selective. */
  ANALYZE;
  DELETE FROM sqlite_stat1;
  INSERT INTO sqlite_stat1 VALUES('t1','t1abc','10000 5000 2000 10');
  ANALYZE sqlite_master;
} {}

# Simple queries that leave the first one or two columns of the
# index unconstrainted.
#
do_execsql_test skipscan1-1.2 {
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-1.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a;
} {/* USING INDEX t1abc (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-1.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.3 {
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a DESC;
} {def 345 9 10 | abc 345 7 8 |}
do_execsql_test skipscan1-1.3eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a DESC;
} {/* USING INDEX t1abc (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-1.3sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a DESC;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.4 {
  SELECT a,b,c,d,'|' FROM t1 WHERE c=6 ORDER BY a, b, c;
} {abc 234 6 7 | bcd 100 6 11 |}
do_execsql_test skipscan1-1.4eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE c=6 ORDER BY a, b, c;
} {/* USING INDEX t1abc (ANY(a) AND ANY(b) AND c=?)*/}
do_execsql_test skipscan1-1.4sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE c=6 ORDER BY a, b, c;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.5 {
  SELECT a,b,c,d,'|' FROM t1 WHERE c IN (6,7) ORDER BY a, b, c;
} {abc 234 6 7 | abc 345 7 8 | bcd 100 6 11 |}
do_execsql_test skipscan1-1.5eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE c IN (6,7) ORDER BY a, b, c;
} {/* USING INDEX t1abc (ANY(a) AND ANY(b) AND c=?)*/}
do_execsql_test skipscan1-1.5sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE c IN (6,7) ORDER BY a, b, c;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.6 {
  SELECT a,b,c,d,'|' FROM t1 WHERE c BETWEEN 6 AND 7 ORDER BY a, b, c;
} {abc 234 6 7 | abc 345 7 8 | bcd 100 6 11 |}
do_execsql_test skipscan1-1.6eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE c BETWEEN 6 AND 7 ORDER BY a, b, c;
} {/* USING INDEX t1abc (ANY(a) AND ANY(b) AND c>? AND c<?)*/}
do_execsql_test skipscan1-1.6sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE c BETWEEN 6 AND 7 ORDER BY a, b, c;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.7 {
  SELECT a,b,c,d,'|' FROM t1 WHERE b IN (234, 345) AND c BETWEEN 6 AND 7
   ORDER BY a, b;
} {abc 234 6 7 | abc 345 7 8 |}
do_execsql_test skipscan1-1.7eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE b IN (234, 345) AND c BETWEEN 6 AND 7
   ORDER BY a, b;
} {/* USING INDEX t1abc (ANY(a) AND b=? AND c>? AND c<?)*/}
do_execsql_test skipscan1-1.7sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE b IN (234, 345) AND c BETWEEN 6 AND 7
   ORDER BY a, b;
} {~/*ORDER BY*/}


# Joins
#
do_execsql_test skipscan1-1.51 {
  CREATE TABLE t1j(x TEXT, y INTEGER);
  INSERT INTO t1j VALUES('one',1),('six',6),('ninty-nine',99);
  INSERT INTO sqlite_stat1 VALUES('t1j',null,'3');
  ANALYZE sqlite_master;
  SELECT x, a, b, c, d, '|' FROM t1j, t1 WHERE c=y ORDER BY +a;
} {six abc 234 6 7 | six bcd 100 6 11 |}
do_execsql_test skipscan1-1.51eqp {
  EXPLAIN QUERY PLAN
  SELECT x, a, b, c, d, '|' FROM t1j, t1 WHERE c=y ORDER BY +a;
} {/* INDEX t1abc (ANY(a) AND ANY(b) AND c=?)*/}

do_execsql_test skipscan1-1.52 {
  SELECT x, a, b, c, d, '|' FROM t1j LEFT JOIN t1 ON c=y ORDER BY +y, +a;
} {one {} {} {} {} | six abc 234 6 7 | six bcd 100 6 11 | ninty-nine {} {} {} {} |}
do_execsql_test skipscan1-1.52eqp {
  EXPLAIN QUERY PLAN
  SELECT x, a, b, c, d, '|' FROM t1j LEFT JOIN t1 ON c=y ORDER BY +y, +a;
} {/* INDEX t1abc (ANY(a) AND ANY(b) AND c=?)*/}

do_execsql_test skipscan1-2.1 {
  CREATE TABLE t2(a TEXT, b INT, c INT, d INT,
                  PRIMARY KEY(a,b,c));
  INSERT INTO t2 SELECT * FROM t1;

  /* Fake the sqlite_stat1 table so that the query planner believes
  ** the table contains thousands of rows and that the first few
  ** columns are not selective. */
  ANALYZE;
  UPDATE sqlite_stat1 SET stat='10000 5000 2000 10' WHERE idx NOT NULL;
  ANALYZE sqlite_master;
} {}

do_execsql_test skipscan1-2.2 {
  SELECT a,b,c,d,'|' FROM t2 WHERE d<>99 AND b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-2.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t2 WHERE d<>99 AND b=345 ORDER BY a;
} {/* USING INDEX sqlite_autoindex_t2_1 (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-2.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t2 WHERE d<>99 AND b=345 ORDER BY a;
} {~/*ORDER BY*/}


do_execsql_test skipscan1-3.1 {
  CREATE TABLE t3(a TEXT, b INT, c INT, d INT,
                  PRIMARY KEY(a,b,c)) WITHOUT ROWID;
  INSERT INTO t3 SELECT * FROM t1;

  /* Fake the sqlite_stat1 table so that the query planner believes
  ** the table contains thousands of rows and that the first few
  ** columns are not selective. */
  ANALYZE;
  UPDATE sqlite_stat1 SET stat='10000 5000 2000 10' WHERE idx NOT NULL;
  ANALYZE sqlite_master;
} {}

do_execsql_test skipscan1-3.2 {
  SELECT a,b,c,d,'|' FROM t3 WHERE b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-3.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t3 WHERE b=345 ORDER BY a;
} {/* PRIMARY KEY (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-3.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t3 WHERE b=345 ORDER BY a;
} {~/*ORDER BY*/}

# Ticket 520070ec7fbaac: Array overrun in the skip-scan optimization
# 2013-12-22
#
do_execsql_test skipscan1-4.1 {
  CREATE TABLE t4(a,b,c,d,e,f,g,h,i);
  CREATE INDEX t4all ON t4(a,b,c,d,e,f,g,h);
  INSERT INTO t4 VALUES(1,2,3,4,5,6,7,8,9);
  ANALYZE;
  DELETE FROM sqlite_stat1;
  INSERT INTO sqlite_stat1 
    VALUES('t4','t4all','655360 163840 40960 10240 2560 640 160 40 10');
  ANALYZE sqlite_master;
  SELECT i FROM t4 WHERE a=1;
  SELECT i FROM t4 WHERE b=2;
  SELECT i FROM t4 WHERE c=3;
  SELECT i FROM t4 WHERE d=4;
  SELECT i FROM t4 WHERE e=5;
  SELECT i FROM t4 WHERE f=6;
  SELECT i FROM t4 WHERE g=7;
  SELECT i FROM t4 WHERE h=8;
} {9 9 9 9 9 9 9 9}

# Make sure skip-scan cost computation in the query planner takes into
# account the fact that the seek must occur multiple times.
#
# Prior to 2014-03-10, the costs were computed incorrectly which would
# cause index t5i2 to be used instead of t5i1 on the skipscan1-5.3.
#
do_execsql_test skipscan1-5.1 {
  CREATE TABLE t5(
    id INTEGER PRIMARY KEY,
    loc TEXT,
    lang INTEGER,
    utype INTEGER,
    xa INTEGER,
    xd INTEGER,
    xh INTEGER
  );
  CREATE INDEX t5i1 on t5(loc, xh, xa, utype, lang);
  CREATE INDEX t5i2 ON t5(xd,loc,utype,lang);
  EXPLAIN QUERY PLAN
    SELECT xh, loc FROM t5 WHERE loc >= 'M' AND loc < 'N';
} {/.*COVERING INDEX t5i1 .*/}
do_execsql_test skipscan1-5.2 {
  ANALYZE;
  DELETE FROM sqlite_stat1;
  DROP TABLE IF EXISTS sqlite_stat4;
  DROP TABLE IF EXISTS sqlite_stat3;
  INSERT INTO sqlite_stat1 VALUES('t5','t5i1','2702931 3 2 2 2 2');
  INSERT INTO sqlite_stat1 VALUES('t5','t5i2','2702931 686 2 2 2');
  ANALYZE sqlite_master;
} {}
db cache flush
do_execsql_test skipscan1-5.3 {
  EXPLAIN QUERY PLAN
    SELECT xh, loc FROM t5 WHERE loc >= 'M' AND loc < 'N';
} {/.*COVERING INDEX t5i1 .*/}

# The column used by the skip-scan needs to be sufficiently selective.
# See the private email from Adi Zaimi to drh@sqlite.org on 2014-09-22.
#
db close
forcedelete test.db
sqlite3 db test.db
do_execsql_test skipscan1-6.1 {
  CREATE TABLE t1(a,b,c,d,e,f,g,h varchar(300));
  CREATE INDEX t1ab ON t1(a,b);
  ANALYZE sqlite_master;
  -- Only two distinct values for the skip-scan column.  Skip-scan is not used.
  INSERT INTO sqlite_stat1 VALUES('t1','t1ab','500000 250000 125000');
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1 WHERE b=1;
} {~/ANY/}
do_execsql_test skipscan1-6.2 {
  -- Four distinct values for the skip-scan column.  Skip-scan is used.
  UPDATE sqlite_stat1 SET stat='500000 250000 62500';
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1 WHERE b=1;
} {/ANY.a. AND b=/}
do_execsql_test skipscan1-6.3 {
  -- Two distinct values for the skip-scan column again.  Skip-scan is not used.
  UPDATE sqlite_stat1 SET stat='500000 125000 62500';
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1 WHERE b=1;
} {~/ANY/}

# If the sqlite_stat1 entry includes the "noskipscan" token, then never use
# skipscan with that index.
#
do_execsql_test skipscan1-7.1 {
  UPDATE sqlite_stat1 SET stat='500000 125000 1 sz=100';
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1 WHERE b=1;
} {/ANY/}
do_execsql_test skipscan1-7.2 {
  UPDATE sqlite_stat1 SET stat='500000 125000 1 noskipscan sz=100';
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1 WHERE b=1;
} {~/ANY/}
do_execsql_test skipscan1-7.3 {
  UPDATE sqlite_stat1 SET stat='500000 125000 1 sz=100 noskipscan';
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN SELECT * FROM t1 WHERE b=1;
} {~/ANY/}

# Ticket 8fd39115d8f46ece70e7d4b3c481d1bd86194746  2015-07-23
# Incorrect code generated for a skipscan within an OR optimization
# on a WITHOUT ROWID table.
#
do_execsql_test skipscan1-8.1 {
  DROP TABLE IF EXISTS t1;
  CREATE TABLE t1(x, y, PRIMARY KEY(x,y)) WITHOUT ROWID;
  INSERT INTO t1(x,y) VALUES(1,'AB');
  INSERT INTO t1(x,y) VALUES(2,'CD');
  ANALYZE;
  DROP TABLE IF EXISTS sqlite_stat4;
  DELETE FROM sqlite_stat1;
  INSERT INTO sqlite_stat1(tbl,idx,stat) VALUES('t1','t1','1000000 100 1');
  ANALYZE sqlite_master;
  SELECT * FROM t1
   WHERE (y = 'AB' AND x <= 4)
      OR (y = 'EF' AND x = 5);
} {1 AB}
do_execsql_test skipscan1-8.1eqp {
  EXPLAIN QUERY PLAN
  SELECT * FROM t1
   WHERE (y = 'AB' AND x <= 4)
      OR (y = 'EF' AND x = 5);
} {/ANY/}
do_execsql_test skipscan1-8.2 {
  SELECT * FROM t1
   WHERE y = 'AB' OR (y = 'CD' AND x = 2)
  ORDER BY +x;
} {1 AB 2 CD}

# Segfault reported on the mailing list by Keith Medcalf on 2016-09-18.
# A skip-scan with a "column IN (SELECT ...)" on the second term of the
# index.
#
do_execsql_test skipscan1-9.2 {
  CREATE TABLE t9a(a,b,c);
  CREATE INDEX t9a_ab ON t9a(a,b);
  CREATE TABLE t9b(x,y);
  ANALYZE sqlite_master;
  INSERT INTO sqlite_stat1 VALUES('t9a','t9a_ab','1000000 250000 1');
  ANALYZE sqlite_master;
  EXPLAIN QUERY PLAN
  SELECT * FROM t9a WHERE b IN (SELECT x FROM t9b WHERE y!=5);
} {/USING INDEX t9a_ab .ANY.a. AND b=./}


optimization_control db skip-scan 0
do_execsql_test skipscan1-9.3 {
  EXPLAIN QUERY PLAN
  SELECT  * FROM t9a WHERE b IN (SELECT x FROM t9b WHERE y!=5);
} {/{SCAN TABLE t9a}/}
optimization_control db skip-scan 1

finish_test