From: drh Date: Tue, 23 Sep 2014 01:40:59 +0000 (+0000) Subject: Adjust skip-scan cost estimates slightly so that a full table scan is X-Git-Tag: version-3.8.7~81 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=14f0e2128ac9cbbe5e1e871372911e3df447df4f;p=thirdparty%2Fsqlite.git Adjust skip-scan cost estimates slightly so that a full table scan is preferred over a skip-scan to a column with only two distinct values. FossilOrigin-Name: ae9a42b268ad3f7d21a5813bb931e795c6917014 --- diff --git a/manifest b/manifest index 625787bf08..aeea9bdb33 100644 --- a/manifest +++ b/manifest @@ -1,5 +1,5 @@ -C Fix\sto\spayload\ssize\soverflow\sdetection\sin\sthe\scellSizePtr()\schange\sof\nthe\sprevious\scheck-in. -D 2014-09-22T20:38:10.316 +C Adjust\sskip-scan\scost\sestimates\sslightly\sso\sthat\sa\sfull\stable\sscan\sis\npreferred\sover\sa\sskip-scan\sto\sa\scolumn\swith\sonly\stwo\sdistinct\svalues. +D 2014-09-23T01:40:59.122 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f F Makefile.in cf57f673d77606ab0f2d9627ca52a9ba1464146a F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23 @@ -302,7 +302,7 @@ F src/vtab.c 019dbfd0406a7447c990e1f7bd1dfcdb8895697f F src/wal.c 10e7de7ce90865a68153f001a61f1d985cd17983 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4 F src/walker.c c253b95b4ee44b21c406e2a1052636c31ea27804 -F src/where.c 3f859ecfada8643ce8255f20d481b5a3e0921662 +F src/where.c a14d3d8042adeb51f81731c1b47b3e481d1cc23a F src/whereInt.h 124d970450955a6982e174b07c320ae6d62a595c F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2 @@ -836,10 +836,10 @@ F test/shortread1.test bb591ef20f0fd9ed26d0d12e80eee6d7ac8897a3 F test/show_speedtest1_rtree.tcl 32e6c5f073d7426148a6936a0408f4b5b169aba5 F test/shrink.test 8c70f62b6e8eb4d54533de6d65bd06b1b9a17868 F test/sidedelete.test f0ad71abe6233e3b153100f3b8d679b19a488329 -F test/skipscan1.test 28c7faa41a0d7265040ecb0a0abd90c0904270b2 +F test/skipscan1.test 7e15e1cc524524e7b2c4595ec85c75501d22f4ff F test/skipscan2.test d1d1450952b7275f0b0a3a981f0230532743951a F test/skipscan3.test ec5bab3f81c7038b43450e7b3062e04a198bdbb5 -F test/skipscan5.test d8b9692b702745a0e41c23f9da6beac81df01196 +F test/skipscan5.test 67817a4b6857c47e0e33ba3e506da6f23ef68de2 F test/soak.test 0b5b6375c9f4110c828070b826b3b4b0bb65cd5f F test/softheap1.test 40562fe6cac6d9827b7b42b86d45aedf12c15e24 F test/sort.test 15e1d3014abc3f6d4357ed81b93b82117aefd235 @@ -1199,7 +1199,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f -P bc8bbf3207288d160287519c3b7123997996b440 -R 5a3408a8ae29b6451a1037ab47048e78 +P 7609744014c6a84a8379794a0351a2e9626ec86b +R cb94e4a1db7c56387373fb77d2698ee3 U drh -Z 93e96edbb124ae02212644cc0f189540 +Z a13a3c1c4006b80e078cd097de2cdb1a diff --git a/manifest.uuid b/manifest.uuid index b44f538e96..c811540af6 100644 --- a/manifest.uuid +++ b/manifest.uuid @@ -1 +1 @@ -7609744014c6a84a8379794a0351a2e9626ec86b \ No newline at end of file +ae9a42b268ad3f7d21a5813bb931e795c6917014 \ No newline at end of file diff --git a/src/where.c b/src/where.c index d1862b499a..40f95acc49 100644 --- a/src/where.c +++ b/src/where.c @@ -4359,11 +4359,14 @@ static int whereLoopAddBtreeIndex( nIter = pProbe->aiRowLogEst[saved_nEq] - pProbe->aiRowLogEst[saved_nEq+1]; if( pTerm ){ /* TUNING: When estimating skip-scan for a term that is also indexable, - ** increase the cost of the skip-scan by 2x, to make it a little less + ** multiply the cost of the skip-scan by 2.0, to make it a little less ** desirable than the regular index lookup. */ nIter += 10; assert( 10==sqlite3LogEst(2) ); } pNew->nOut -= nIter; + /* TUNING: Because uncertainties in the estimates for skip-scan queries, + ** add a 1.375 fudge factor to make skip-scan slightly less likely. */ + nIter += 5; whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul); pNew->nOut = saved_nOut; pNew->u.btree.nEq = saved_nEq; diff --git a/test/skipscan1.test b/test/skipscan1.test index 8150b012f6..6b9f1209a5 100644 --- a/test/skipscan1.test +++ b/test/skipscan1.test @@ -245,6 +245,32 @@ do_execsql_test skipscan1-5.3 { 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/} finish_test diff --git a/test/skipscan5.test b/test/skipscan5.test index 5d6d392998..7c3b166a8c 100644 --- a/test/skipscan5.test +++ b/test/skipscan5.test @@ -108,7 +108,7 @@ foreach {tn dbenc coll} { 3 { c > 'q' } {/*ANY(a) AND ANY(b) AND c>?*/} 4 { c > 'e' } {/*SCAN TABLE t2*/} 5 { c < 'q' } {/*SCAN TABLE t2*/} - 4 { c < 'e' } {/*ANY(a) AND ANY(b) AND c