-C The\sANALYZE\scommand\sautomatically\sappends\s"noskipscan"\sto\ssqlite_stat1\sentries\nthat\shave\slarge\sworst-case\srepeat\sestimates\sbut\ssmall\saverage\srepeat\sestimates.
-D 2016-02-29T21:27:16.923
+C Improvements\sto\sthe\slogic\sfor\sadding\sthe\s"noskipscan"\sflag\sto\sstat1\sentries.
+D 2016-02-29T23:02:50.488
F Makefile.in 4e90dc1521879022aa9479268a4cd141d1771142
F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
F Makefile.msc 4f319afb7c049d40aff7af6e8c4e7cc2ba18e079
F sqlite3.1 fc7ad8990fc8409983309bb80de8c811a7506786
F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
F src/alter.c 44e18dfd78e8942d65d3cdaec4de972b5cd9f1f2
-F src/analyze.c 95b2e37e92cbeb9093700b8248e1ec73b3da417b
+F src/analyze.c 997b0ce0f4efd68b0499f941ebebdd1ec0c71549
F src/attach.c a3724c64de1099d85e30751213d285752aed9505
F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
F src/backup.c f60f0aa55d25d853ffde53d0b0370a7bb7ee41ce
F test/shrink.test 1b4330b1fd9e818c04726d45cb28db73087535ce
F test/sidedelete.test f0ad71abe6233e3b153100f3b8d679b19a488329
F test/skipscan1.test d37a75b4be4eb9dedeb69b4f38b1d0a74b5021d7
-F test/skipscan2.test d1d1450952b7275f0b0a3a981f0230532743951a
+F test/skipscan2.test 9fb533b9b66d33d5036fa86bbad1c1ae20861a3f
F test/skipscan3.test ec5bab3f81c7038b43450e7b3062e04a198bdbb5
F test/skipscan5.test 67817a4b6857c47e0e33ba3e506da6f23ef68de2
F test/skipscan6.test 5866039d03a56f5bd0b3d172a012074a1d90a15b
F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5a0143c94ec0682798f3c09fba63593e695d2e2d
-R 177b6cf14f8f11e0a114dc66d2d822d0
+P 6326ba5891fae9c6be0c0c51cebcbe44c9f3f057
+R d11c7934d7e6b9fd5164f25abb15ccbc
U drh
-Z ca3d3ef3ca17a24048e080e522e9cbee
+Z e3fa57a0ace16605a0bcfe31fb8b1cb6
** * "WHERE a=?" matches 10 rows, and
** * "WHERE a=? AND b=?" matches 2 rows.
**
- ** Use the worst-case estimate: the maximum number of repeated entries
- ** in the index. The worst-case estimate is best for picking indexes.
- ** But for skip-scan, we want an average case estimate. The worst-case
- ** estimate might be too high. To avoid undesirable skip-scans, if the
- ** worst-case estimate is above the WHERE_SKIPSCAN_ONSET but the average
- ** estimate is below, simply disable skipscans on this index by adding
- ** the "noskipscan" modifier onto the end of the stat line.
+ ** A worst-case estimate is used: the maximum number of rows that
+ ** could be select for any set of query parameters. The worst case
+ ** is the estimate we want for choosing indexes.
+ **
+ ** For deciding whether or not to do a skip-scan, we want to know the
+ ** average number of rows with the same key. We can approximate this
+ ** using the (worst case) most number of rows with the same key. But
+ ** sometimes that approximation can be badly off. In those cases,
+ ** mark the index as "noskipscan" to avoid suboptimal skip-scan plans.
*/
char *z;
int i;
sqlite3_snprintf(24, z, " %llu", iVal);
z += sqlite3Strlen30(z);
assert( p->current.anEq[i] );
- if( i>0 && iVal>=WHERE_SKIPSCAN_ONSET+5 ){
- iVal = p->current.anDLt[i];
- iVal = (p->nRow + iVal)/(iVal + 1);
- if( iVal<WHERE_SKIPSCAN_ONSET-5 ) noSkipScan = 1;
+ if( iVal>=WHERE_SKIPSCAN_ONSET
+ && p->current.anDLt[i] > p->nRow/(WHERE_SKIPSCAN_ONSET*2/3)
+ ){
+ noSkipScan = 1;
}
}
if( noSkipScan ) sqlite3_snprintf(14, z, " noskipscan");
INSERT INTO people VALUES('Robert','student',159);
INSERT INTO people VALUES('Sally','student',166);
INSERT INTO people VALUES('Tom','student',171);
+/*
INSERT INTO people VALUES('Ursula','student',170);
INSERT INTO people VALUES('Vance','student',179);
INSERT INTO people VALUES('Willma','student',175);
INSERT INTO people VALUES('Xavier','teacher',185);
INSERT INTO people VALUES('Yvonne','student',149);
INSERT INTO people VALUES('Zach','student',170);
+*/
}
# Without ANALYZE, a skip-scan is not used
#
do_execsql_test skipscan2-1.3 {
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ SELECT name FROM people WHERE height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-1.3eqp {
EXPLAIN QUERY PLAN
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
+ SELECT name FROM people WHERE height<=161 ORDER BY +name;
} {~/*INDEX people_idx1 */}
# Now do an ANALYZE. A skip-scan can be used after ANALYZE.
}
db cache flush
do_execsql_test skipscan2-1.5 {
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ SELECT name FROM people WHERE height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-1.5eqp {
EXPLAIN QUERY PLAN
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
+ SELECT name FROM people WHERE height<=161 ORDER BY +name;
} {/*INDEX people_idx1 */}
# Same answer with other formulations of the same query
do_execsql_test skipscan2-1.6 {
SELECT name FROM people
WHERE role IN (SELECT DISTINCT role FROM people)
- AND height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ AND height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-1.7 {
- SELECT name FROM people WHERE role='teacher' AND height>=180
+ SELECT name FROM people WHERE role='teacher' AND height<=161
UNION ALL
- SELECT name FROM people WHERE role='student' AND height>=180
+ SELECT name FROM people WHERE role='student' AND height<=161
ORDER BY 1;
-} {David Jack Patrick Quiana Xavier}
+} {Alice Bob Cindy Emily Megan Olivia Robert}
-# Add 8 more people, bringing the total to 34. Then the number of
-# duplicates in the left-column of the index will be 17 and
-# skip-scan should not be used after an (unfudged) ANALYZE.
+# Add more people so that the estimated number of rows per key is
+# equal to the skip-scan threshold of 18. Then run an (unfudged)
+# ANALYZE. skip-scan should work.
#
do_execsql_test skipscan2-1.8 {
- INSERT INTO people VALUES('Angie','student',166);
- INSERT INTO people VALUES('Brad','student',176);
- INSERT INTO people VALUES('Claire','student',168);
- INSERT INTO people VALUES('Donald','student',162);
- INSERT INTO people VALUES('Elaine','student',177);
- INSERT INTO people VALUES('Frazier','student',159);
- INSERT INTO people VALUES('Grace','student',179);
- INSERT INTO people VALUES('Horace','student',166);
+ INSERT INTO people VALUES('Ursula','student',170);
ANALYZE;
SELECT stat FROM sqlite_stat1 WHERE idx='people_idx1';
-} {{34 17 2}}
+} {{21 18 3}}
db cache flush
do_execsql_test skipscan2-1.9 {
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ SELECT name FROM people WHERE height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-1.9eqp {
EXPLAIN QUERY PLAN
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
+ SELECT name FROM people WHERE height<=161 ORDER BY +name;
} {~/*INDEX people_idx1 */}
-# Add 2 more people, bringing the total to 36. Then the number of
-# duplicates in the left-column of the index will be 18 and
-# skip-scan will be used after an (unfudged) ANALYZE.
-#
-do_execsql_test skipscan2-1.10 {
- INSERT INTO people VALUES('Ingrad','student',155);
- INSERT INTO people VALUES('Jacob','student',179);
- ANALYZE;
- SELECT stat FROM sqlite_stat1 WHERE idx='people_idx1';
-} {{36 18 2}}
-db cache flush
-do_execsql_test skipscan2-1.11 {
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
-do_execsql_test skipscan2-1.11eqp {
- EXPLAIN QUERY PLAN
- SELECT name FROM people WHERE height>=180 ORDER BY +name;
-} {/*INDEX people_idx1 */}
-
# Repeat using a WITHOUT ROWID table.
#
INSERT INTO peoplew(name,role,height)
SELECT name, role, height FROM people;
ALTER TABLE people RENAME TO old_people;
- SELECT name FROM peoplew WHERE height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ SELECT name FROM peoplew WHERE height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-2.2 {
SELECT name FROM peoplew
WHERE role IN (SELECT DISTINCT role FROM peoplew)
- AND height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ AND height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-2.2 {
- SELECT name FROM peoplew WHERE role='teacher' AND height>=180
+ SELECT name FROM peoplew WHERE role='teacher' AND height<=161
UNION ALL
- SELECT name FROM peoplew WHERE role='student' AND height>=180
+ SELECT name FROM peoplew WHERE role='student' AND height<=161
ORDER BY 1;
-} {David Jack Patrick Quiana Xavier}
+} {Alice Bob Cindy Emily Megan Olivia Robert}
# Now do an ANALYZE. A skip-scan can be used after ANALYZE.
#
}
db cache flush
do_execsql_test skipscan2-2.5 {
- SELECT name FROM peoplew WHERE height>=180 ORDER BY +name;
-} {David Jack Patrick Quiana Xavier}
+ SELECT name FROM peoplew WHERE height<=161 ORDER BY +name;
+} {Alice Bob Cindy Emily Megan Olivia Robert}
do_execsql_test skipscan2-2.5eqp {
EXPLAIN QUERY PLAN
- SELECT name FROM peoplew WHERE height>=180 ORDER BY +name;
+ SELECT name FROM peoplew WHERE height<=161 ORDER BY +name;
} {/*INDEX peoplew_idx1 */}
# A skip-scan on a PK index of a WITHOUT ROWID table.
projects / thirdparty / sqlite.git / commitdiff
