Improved comments, including a typo fix, on the whereLoopCheaperProperSubset()

function.

FossilOrigin-Name: 700a3c694438ca6cca185d0097f24799e82717ef38cb47bd83666c80f0e3cb2f

diff --git a/manifest b/manifest
index b77b1484ce23d17c6138e2aba2dbeb11c34b60cf..ab44e57d39c86649e8e8efbc46d2713c6b4725ac 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C In\sthe\squery\splanner,\sdo\snot\sconsider\sindex\sX\sto\sbe\sa\sproper\ssubset\sof\s\nindex\sY\sif\sX\sis\sa\scovering\sindex\sbut\sY\sis\snot.
-D 2017-10-15T22:16:25.229
+C Improved\scomments,\sincluding\sa\stypo\sfix,\son\sthe\swhereLoopCheaperProperSubset()\nfunction.
+D 2017-10-16T11:50:12.951
 F Makefile.in e016061b23e60ac9ec27c65cb577292b6bde0307ca55abd874ab3487b3b1beb2
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 37740aba9c4bb359c627eadccf1cfd7be4f5f847078723777ea7763969e533b1
@@ -544,7 +544,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 839db09792fead5052bb35e533fa485e134913d547d05b5f42e537b73e63f07a
 F src/wal.h 8de5d2d3de0956d6f6cb48c83a4012d5f227b8fe940f3a349a4b7e85ebcb492a
 F src/walker.c 3ccfa8637f95355bff61144e01a615b8ef26f79c312880848da73f03367da1e6
-F src/where.c 248f0dc6085b37b4b2ccad2de06b90f1a48b1932403ab0ad9100a1f2a6990763
+F src/where.c d8c6d690c4b11f30211de073011fe19352364a6303ae053f45cb66f9576ba8a9
 F src/whereInt.h 82c04c5075308abbac59180c8bad5ecb45b07453981f60a53f3c7dee21e1e971
 F src/wherecode.c e8c2ece5843ea56e6c90277d421f2d628f3f7b7c976642369cc519f008e1d2b1
 F src/whereexpr.c afcac9cccfc0fdaccbdda94034a398947b6dc47dbf821c1b496261722832a6a4
@@ -1664,7 +1664,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ac8786f3f9f35cb6fa72c65f5ca41cc6659f4702cd29ab0c9dcf04d3d1189090
-R 88b26813bcaf999746e4cf55503b4797
+P ee31c04353cd75ea4bbadee2994c30d3808b696a4f680187502d104902988a5d
+R 593b5394fda7f5c3a7e7e5312c0a0c37
 U drh
-Z fe6d8478e3f31cb2dfbec6ce858d4ad8
+Z d6213a58e95c0fa7e25d95c2efa3d8ac

diff --git a/manifest.uuid b/manifest.uuid
index 12179a84a0ad31f08c4b6c43c41bd4fac0c1a5d3..3281f881f9a8d1bb887ff767103bdc104b4a2ab3 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ee31c04353cd75ea4bbadee2994c30d3808b696a4f680187502d104902988a5d
\ No newline at end of file
+700a3c694438ca6cca185d0097f24799e82717ef38cb47bd83666c80f0e3cb2f
\ No newline at end of file

diff --git a/src/where.c b/src/where.c
index 95bbdb157efc17211b6918d03e27940d2300e82a..6021edf47fa395e25948985a4a786b696b5bc6fa 100644 (file)
--- a/src/where.c
+++ b/src/where.c
@@ -1885,7 +1885,7 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
 ** Return TRUE if all of the following are true:
 **
 **   (1)  X has the same or lower cost that Y
-**   (2)  X users fewer WHERE clause terms than Y
+**   (2)  X uses fewer WHERE clause terms than Y
 **   (3)  Every WHERE clause term used by X is also used by Y
 **   (4)  X skips at least as many columns as Y
 **   (5)  If X is a covering index, than Y is too
@@ -1895,7 +1895,9 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
 ** to have a lower cost.  This routine returns TRUE when that cost 
 ** relationship is inverted and needs to be adjusted.  Constraint (4)
 ** was added because if X uses skip-scan less than Y it still might
-** deserve a lower cost even if it is a proper subset of Y.
+** deserve a lower cost even if it is a proper subset of Y.  Constraint (5)
+** was added because a covering index probably deserves to have a lower cost
+** than a non-covering index even if it is a proper subset.
 */
 static int whereLoopCheaperProperSubset(
   const WhereLoop *pX,       /* First WhereLoop to compare */