Prefer to use partial indexes for full table scans when that is possible.

FossilOrigin-Name: fe1874321ba31cec9ae65387920c33d8d0178ed8

diff --git a/manifest b/manifest
index b9ef6e83efe82032ad069391367c9510e0595220..718d324c20fd44f9bf79e1b011dce6af9f89852a 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sthe\s"dbhash.exe"\sutility\sprogram\sthat\scomputes\sa\sSHA1\shash\sover\sthe\ninvariant\scontent\sof\san\sSQLite\sdatabase\sfile.\s\sFree\sspace\sin\sthe\sfile,\sthe\npage\ssize,\sauto_vacuum\sstatus,\stext\sencoding,\sand\sso\sforth\sdo\snot\schange\sthe\nhash.\s\sOnly\sthe\scontent\smatters.
-D 2016-06-08T14:04:50.483
+C Prefer\sto\suse\spartial\sindexes\sfor\sfull\stable\sscans\swhen\sthat\sis\spossible.
+D 2016-06-08T18:07:21.900
 F Makefile.in f3f7d2060ce03af4584e711ef3a626ef0b1d6340
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 50149765ef72f4e652b9a0f1f6462c4784bb9423
@@ -329,7 +329,7 @@ F src/btmutex.c bc87dd3b062cc26edfe79918de2200ccb8d41e73
 F src/btree.c 2781fb1db1e46390a9c27a2162395f371577ac66
 F src/btree.h 2107a2630e02c8cba58bb12ce14e731e734ea29c
 F src/btreeInt.h c18b7d2a3494695133e4e60ee36061d37f45d9a5
-F src/build.c e827e57e4a29c00e8429c5fd4d9d4572cb1b32a4
+F src/build.c 535879738a9f9e351624ebe827bdfb6ef16475ae
 F src/callback.c 2e76147783386374bf01b227f752c81ec872d730
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c 999a828425b35b8092a8cde25690e71c20906344
@@ -462,7 +462,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 02eeecc265f6ffd0597378f5d8ae9070b62a406a
 F src/wal.h 2f7c831cf3b071fa548bf2d5cac640846a7ff19c
 F src/walker.c 0f142b5bd3ed2041fc52d773880748b212e63354
-F src/where.c b9f5b0ddb14c3827e70b5379e659cf4cfd524c4d
+F src/where.c 74f0798525b6306682d7234f230ea93f86959b9b
 F src/whereInt.h e5b939701a7ceffc5a3a8188a37f9746416ebcd0
 F src/wherecode.c ba71a4e4bada29aa9842200e6299714bf18c812c
 F src/whereexpr.c c32d47085dbaca0b8fd013210f56693c7d220d48
@@ -840,7 +840,7 @@ F test/index2.test f835d5e13ca163bd78c4459ca15fd2e4ed487407
 F test/index3.test 81bc47890b8abfb181bc35f8d10b56c069803386
 F test/index4.test ab92e736d5946840236cd61ac3191f91a7856bf6
 F test/index5.test 8621491915800ec274609e42e02a97d67e9b13e7
-F test/index6.test 7102ec371414c42dfb1d5ca37eb4519aa9edc23a
+F test/index6.test 43b4e29258b978fcdab84fc61df4f5212119dd09
 F test/index7.test 9c6765a74fc3fcde7aebc5b3bd40d98df14a527c
 F test/indexedby.test 9c4cd331224e57f79fbf411ae245e6272d415985
 F test/indexexpr1.test cb71b6586177b840e28110dd952178bb2bdfedc2
@@ -1501,8 +1501,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 2091a4c9231c7871f27661adc27dd7df26500f6c fb2768154c513881886e89801e906bea959197b3
-R 654981991ade95156b7aa25e1b0590de
-T +closed fb2768154c513881886e89801e906bea959197b3
+P f48a4ad33ecd4a86f5529596ff11829ba38b0875
+R f8f1ecf8d68a5747b29b0c8ae33faacb
 U drh
-Z 4625be77e802d56f2b1c496e15a4bd85
+Z bc2339201021198d1e3ee60eab532825

diff --git a/manifest.uuid b/manifest.uuid
index 7e4bb144b7565a6552d5a74a3acf962440db6eb9..e6930e8d093c0501b15f01741a5cf2d3e20cec64 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-f48a4ad33ecd4a86f5529596ff11829ba38b0875
\ No newline at end of file
+fe1874321ba31cec9ae65387920c33d8d0178ed8
\ No newline at end of file

diff --git a/src/build.c b/src/build.c
index a5931954ad332e86dbe00e65cd6958d2248c8a03..c32195f6550d0ae9779c0f102046490cf95e4d78 100644 (file)
--- a/src/build.c
+++ b/src/build.c
@@ -3434,10 +3434,11 @@ void sqlite3DefaultRowEst(Index *pIdx){
   int i;
 
   /* Set the first entry (number of rows in the index) to the estimated 
-  ** number of rows in the table. Or 10, if the estimated number of rows 
-  ** in the table is less than that.  */
+  ** number of rows in the table, or half the number of rows in the table
+  ** for a partial index.   But do not let the estimate drop below 10. */
   a[0] = pIdx->pTable->nRowLogEst;
-  if( a[0]<33 ) a[0] = 33;        assert( 33==sqlite3LogEst(10) );
+  if( pIdx->pPartIdxWhere!=0 ) a[0] -= 10;  assert( 10==sqlite3LogEst(2) );
+  if( a[0]<33 ) a[0] = 33;                  assert( 33==sqlite3LogEst(10) );
 
   /* Estimate that a[1] is 10, a[2] is 9, a[3] is 8, a[4] is 7, a[5] is
   ** 6 and each subsequent value (if any) is 5.  */

diff --git a/src/where.c b/src/where.c
index 04d0b0190c9e96b8267c9e3266acab59c447f64c..e5a476c00aa12323e1bb07387b21c5afd30de07e 100644 (file)
--- a/src/where.c
+++ b/src/where.c
@@ -2761,6 +2761,7 @@ static int whereLoopAddBtree(
       /* Full scan via index */
       if( b
        || !HasRowid(pTab)
+       || pProbe->pPartIdxWhere!=0
        || ( m==0
          && pProbe->bUnordered==0
          && (pProbe->szIdxRow<pTab->szTabRow)

diff --git a/test/index6.test b/test/index6.test
index 33ae3d1cb11f7f5a945716b7a197490edfa0f130..9501a6c86467a92555da098ca4559c80e607635a 100644 (file)
--- a/test/index6.test
+++ b/test/index6.test
@@ -376,4 +376,15 @@ do_execsql_test index6-10.3eqp {
   SELECT e FROM t10 WHERE a=1 AND b=2 ORDER BY d DESC;
 } {~/USING INDEX t10x/}
 
+# A partial index will be used for a full table scan, where possible
+do_execsql_test index6-11.1 {
+  CREATE TABLE t11(a,b,c);
+  CREATE INDEX t11x ON t11(a) WHERE b<>99;
+  EXPLAIN QUERY PLAN SELECT a FROM t11 WHERE b<>99;
+} {/USING INDEX t11x/}
+do_execsql_test index6-11.2 {
+  EXPLAIN QUERY PLAN SELECT a FROM t11 WHERE b<>99 AND c<>98;
+} {/USING INDEX t11x/}
+  
+
 finish_test