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Overview
Comment: | Do a better job of choosing the join table order when the tables having very different numbers of rows. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
952f5e8c69904c48f2decfabf8ea60a2 |
User & Date: | drh 2011-03-04 00:56:58.067 |
References
2011-03-04
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01:23 | Backport the query planner enhancement of [952f5e8c69904] to the 3.7.2 branch. (check-in: 440d995661 user: drh tags: branch-3.7.2) | |
Context
2011-03-05
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13:54 | Fix an instance of signed arithmetic overflow and an one bit-shift overflow. Mark six other signed arithmetic overflow locations that need fixing. (check-in: 04abab71ec user: drh tags: trunk) | |
2011-03-04
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00:56 | Do a better job of choosing the join table order when the tables having very different numbers of rows. (check-in: 952f5e8c69 user: drh tags: trunk) | |
2011-03-02
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22:07 | Fix quoting of the result in rtreeB.test. (check-in: c6532b35cc user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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4606 4607 4608 4609 4610 4611 4612 | } /* Conditions under which this table becomes the best so far: ** ** (1) The table must not depend on other tables that have not ** yet run. ** | | | > | 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 | } /* Conditions under which this table becomes the best so far: ** ** (1) The table must not depend on other tables that have not ** yet run. ** ** (2) A full-table-scan plan cannot supercede indexed plan unless ** the full-table-scan is an "optimal" plan as defined above. ** ** (3) All tables have an INDEXED BY clause or this table lacks an ** INDEXED BY clause or this table uses the specific ** index specified by its INDEXED BY clause. This rule ensures ** that a best-so-far is always selected even if an impossible ** combination of INDEXED BY clauses are given. The error ** will be detected and relayed back to the application later. ** The NEVER() comes about because rule (2) above prevents ** An indexable full-table-scan from reaching rule (3). ** ** (4) The plan cost must be lower than prior plans or else the ** cost must be the same and the number of rows must be lower. */ if( (sCost.used¬Ready)==0 /* (1) */ && (bestJ<0 || (notIndexed&m)!=0 /* (2) */ || (bestPlan.plan.wsFlags & WHERE_NOT_FULLSCAN)==0 || (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0) && (nUnconstrained==0 || pTabItem->pIndex==0 /* (3) */ || NEVER((sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0)) && (bestJ<0 || sCost.rCost<bestPlan.rCost /* (4) */ || (sCost.rCost<=bestPlan.rCost && sCost.plan.nRow<bestPlan.plan.nRow)) ){ |
︙ | ︙ |
Added test/analyze6.test.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | # 2011 March 3 # # 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 for SQLite library. The focus of the tests # in this file a corner-case query planner optimization involving the # join order of two tables of different sizes. # set testdir [file dirname $argv0] source $testdir/tester.tcl ifcapable !stat2 { finish_test return } set testprefix analyze6 proc eqp {sql {db db}} { uplevel execsql [list "EXPLAIN QUERY PLAN $sql"] $db } do_test analyze6-1.0 { db eval { CREATE TABLE cat(x INT); CREATE UNIQUE INDEX catx ON cat(x); /* Give cat 16 unique integers */ INSERT INTO cat VALUES(1); INSERT INTO cat VALUES(2); INSERT INTO cat SELECT x+2 FROM cat; INSERT INTO cat SELECT x+4 FROM cat; INSERT INTO cat SELECT x+8 FROM cat; CREATE TABLE ev(y INT); CREATE INDEX evy ON ev(y); /* ev will hold 32 copies of 16 integers found in cat */ INSERT INTO ev SELECT x FROM cat; INSERT INTO ev SELECT x FROM cat; INSERT INTO ev SELECT y FROM ev; INSERT INTO ev SELECT y FROM ev; INSERT INTO ev SELECT y FROM ev; INSERT INTO ev SELECT y FROM ev; ANALYZE; SELECT count(*) FROM cat; SELECT count(*) FROM ev; } } {16 512} # The lowest cost plan is to scan CAT and for each integer there, do a single # lookup of the first corresponding entry in EV then read off the equal values # in EV. (Prior to the 2011-03-04 enhancement to where.c, this query would # have used EV for the outer loop instead of CAT - which was about 3x slower.) # do_test analyze6-1.1 { eqp {SELECT count(*) FROM ev, cat WHERE x=y} } {0 0 1 {SCAN TABLE cat (~16 rows)} 0 1 0 {SEARCH TABLE ev USING COVERING INDEX evy (y=?) (~32 rows)}} # The same plan is chosen regardless of the order of the tables in the # FROM clause. # do_test analyze6-1.2 { eqp {SELECT count(*) FROM cat, ev WHERE x=y} } {0 0 0 {SCAN TABLE cat (~16 rows)} 0 1 1 {SEARCH TABLE ev USING COVERING INDEX evy (y=?) (~32 rows)}} finish_test |