When the sqlite_stat1 data is missing for some indexes of a table but is

present for the table itself or for other indexes in the same table, then do
not let the estimated number of rows in that table get too small, as
doing so can deceive the query planner into ignoring a perfectly good index.

FossilOrigin-Name: 98d4262018a81a9a36dd8beb4b02ff0e75cdcbb8a121d143157ffb37b228d60d

diff --git a/manifest b/manifest
index b3792caebee8743f658e012414224395a868c332..43afb8af6e434ae24341e58a217f96855249516f 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Small\sperformance\simprovement\sand\ssize\sreduction\sin\sthe\sexpression\ncode\sgenerator.
-D 2020-05-27T12:44:28.447
+C When\sthe\ssqlite_stat1\sdata\sis\smissing\sfor\ssome\sindexes\sof\sa\stable\sbut\sis\npresent\sfor\sthe\stable\sitself\sor\sfor\sother\sindexes\sin\sthe\ssame\stable,\sthen\sdo\nnot\slet\sthe\sestimated\snumber\sof\srows\sin\sthat\stable\sget\stoo\ssmall,\sas\ndoing\sso\scan\sdeceive\sthe\squery\splanner\sinto\signoring\sa\sperfectly\sgood\sindex.
+D 2020-05-28T00:45:16.053
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -477,7 +477,7 @@ F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
 F src/btree.c f14e415fcfd0b52b4e4ebd193ba5fadac5e8252c30f023389af682813af44025
 F src/btree.h 989ef3c33413549e3e148f3dcb46c030f317dac130dc86809ba6b9aa4b16c72a
 F src/btreeInt.h 5c8b8749805787313ecf49eb5be3ced1e94bbf8ef54bb01470ce6bd0d5185c67
-F src/build.c ca9e7a33b74f1bf2eb3a5f37f9d07dfed335469f2d70c0bd350e0dd42a50183a
+F src/build.c 1c3dec6d36ddc697dbc1df04100687cdbbed65aacfda067d1e9632e4102e9999
 F src/callback.c d0b853dd413255d2e337b34545e54d888ea02f20da5ad0e63585b389624c4a6c
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c e98518d2d3d4029a13c805e07313fb60c877be56db76e90dd5f3af73085d0ce6
@@ -782,7 +782,7 @@ F test/corruptJ.test 4d5ccc4bf959464229a836d60142831ef76a5aa4
 F test/corruptK.test 5b4212fe346699831c5ad559a62c54e11c0611bdde1ea8423a091f9c01aa32af
 F test/corruptL.test 13ef74a93223af25015d223add0df4c2d375f0b958b546a2a72033f2fdab7a70
 F test/corruptM.test 7d574320e08c1b36caa3e47262061f186367d593a7e305d35f15289cc2c3e067
-F test/cost.test 51f4fcaae6e78ad5a57096831259ed6c760e2ac6876836e91c00030fad385b34
+F test/cost.test 1d156ce9858780a966c062694687afe0343a0ed12d081d071fb57027e726bafc
 F test/count.test e0699a15712bc2a4679d60e408921c2cce7f6365a30340e790c98e0f334a9c77
 F test/countofview.test e17d6e6688cf74f22783c9ec6e788c0790ee4fbbaee713affd00b1ac0bb39b86
 F test/coveridxscan.test 5ec98719a2e2914e8908dc75f7247d9b54a26df04625f846ac7900d5483f7296
@@ -1067,7 +1067,7 @@ F test/index3.test 51685f39345462b84fcf77eb8537af847fdf438cc96b05c45d6aaca4e473a
 F test/index4.test ab92e736d5946840236cd61ac3191f91a7856bf6
 F test/index5.test 8621491915800ec274609e42e02a97d67e9b13e7
 F test/index6.test f172653b35b20233e59200e8b92a76db61bf7285437bf777b93b306ba26a47e7
-F test/index7.test 1d764c0cca45f5a76150b08e127ccc8d52492cfa788b5fafed4be784a351b020
+F test/index7.test b8a0ba2110fd517bb48c4e76d26d60f1ab2ed9e257b18d71f820d7e71e9f8570
 F test/index8.test bc2e3db70e8e62459aaa1bd7e4a9b39664f8f9d7
 F test/index9.test 0aa3e509dddf81f93380396e40e9bb386904c1054924ba8fa9bcdfe85a8e7721
 F test/indexedby.test a52c8c6abfae4fbfb51d99440de4ca1840dbacc606b05e29328a2a8ba7cd914e
@@ -1866,7 +1866,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5b560ec49041d89c87ea3315d8fc17f7fb0e03a82091934be7373b290183f82e
-R 49a1e2497fcf7da09e39544b00e72660
+P eeb53e219551d8a05a87f1de9a7cd9af295d08a296f1f435a8509ea1252ccdcc
+R 3d5c5e3daaf0dbc29f6c7d64057e20af
 U drh
-Z 247f47fe4deb86e087e29547910405d2
+Z e68e2bba0e62e900331d67a29c0ab0bb

diff --git a/manifest.uuid b/manifest.uuid
index 4069128f8b428e8c8904327b44e564266488148f..7248988b8e0880859ac1a0c66804e351486d36b7 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-eeb53e219551d8a05a87f1de9a7cd9af295d08a296f1f435a8509ea1252ccdcc
\ No newline at end of file
+98d4262018a81a9a36dd8beb4b02ff0e75cdcbb8a121d143157ffb37b228d60d
\ No newline at end of file

diff --git a/src/build.c b/src/build.c
index 6ff595c6237fea2d018b214edf45cf61f1197312..877db050849bfd2e85db6d4dc9cd4ee35e466896 100644 (file)
--- a/src/build.c
+++ b/src/build.c
@@ -4047,9 +4047,10 @@ exit_create_index:
 ** are based on typical values found in actual indices.
 */
 void sqlite3DefaultRowEst(Index *pIdx){
-  /*                10,  9,  8,  7,  6 */
-  LogEst aVal[] = { 33, 32, 30, 28, 26 };
+               /*                10,  9,  8,  7,  6 */
+  static const LogEst aVal[] = { 33, 32, 30, 28, 26 };
   LogEst *a = pIdx->aiRowLogEst;
+  LogEst x;
   int nCopy = MIN(ArraySize(aVal), pIdx->nKeyCol);
   int i;
 
@@ -4058,10 +4059,21 @@ void sqlite3DefaultRowEst(Index *pIdx){
 
   /* Set the first entry (number of rows in the index) to the estimated 
   ** 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( pIdx->pPartIdxWhere!=0 ) a[0] -= 10;  assert( 10==sqlite3LogEst(2) );
-  if( a[0]<33 ) a[0] = 33;                  assert( 33==sqlite3LogEst(10) );
+  ** for a partial index.
+  **
+  ** 2020-05-27:  If some of the stat data is coming from the sqlite_stat1
+  ** table but other parts we are having to guess at, then do not let the
+  ** estimated number of rows in the table be less than 1000 (LogEst 99).
+  ** Failure to do this can cause the indexes for which we do not have
+  ** stat1 data to be ignored by the query planner.  tag-20200527-1
+  */
+  x = pIdx->pTable->nRowLogEst;
+  assert( 99==sqlite3LogEst(1000) );
+  if( x<99 ){
+    pIdx->pTable->nRowLogEst = x = 99;
+  }
+  if( pIdx->pPartIdxWhere!=0 ) x -= 10;  assert( 10==sqlite3LogEst(2) );
+  a[0] = x;
 
   /* 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/test/cost.test b/test/cost.test
index 2922a0a054dd1da2746eb1b638e5eb76d9783919..592973ab56f6fcd51dd899039babaf6f4c77c165 100644 (file)
--- a/test/cost.test
+++ b/test/cost.test
@@ -230,10 +230,10 @@ do_test 9.2 {
 set L [list a=? b=? c=? d=? e=? f=? g=? h=? i=? j=?]
 foreach {tn nTerm nRow} {
   1   1 10
-  2   2  9
+  2   2 10
   3   3  8
   4   4  7
-  5   5  6
+  5   5  7
   6   6  5
   7   7  5
   8   8  5

diff --git a/test/index7.test b/test/index7.test
index f57792e4c211b7ab404cb9b87d01970f9dee8707..084e8c3c7d828501cf60b670dbd99b8c7c6f6223 100644 (file)
--- a/test/index7.test
+++ b/test/index7.test
@@ -339,5 +339,17 @@ do_execsql_test index7-7.1 {
   SELECT * FROM t6 WHERE y IS TRUE ORDER BY x;
 } {1 1}
 
+# 2020-05-27.  tag-20200527-1.
+# Incomplete stat1 information on a table with few rows should still use the
+# index.
+reset_db
+do_execsql_test index7-8.1 {
+  CREATE TABLE t1(x INTEGER PRIMARY KEY, y);
+  CREATE INDEX t1y ON t1(y) WHERE y IS NOT NULL;
+  INSERT INTO t1(x) VALUES(1),(2);
+  ANALYZE;
+  EXPLAIN QUERY PLAN SELECT 1 FROM t1 WHERE y=5;
+} {/SEARCH TABLE t1 USING COVERING INDEX t1y/}
+
 
 finish_test