Improved query optimization for multi-column indexes where the second or

later columns are constrained by an IN operator and the earlier index columns
limit the search to a small number of rows.  Use the new OP_SeekScan opcode
which does scanning of the relevant range of the index but gives up and
falls back to doing a seek if the number of rows scanned grows to large,
in order to guard against pathological cases where the estimated number
of rows to be scanned is far too small.

FossilOrigin-Name: 4a43430fd23f88352c33b29c4c105b72f6dc821f94bf362040c41a1648c402e5

diff --cc manifest
index 5d4357f4dc1d75cb390a24a3bc10e9eba5375b66,59691be9f56d98cb0fea625b78236a836c195e8f..c14de66d65c5202b681ff8950d28c78fe5889d61
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Back\sout\sthe\sincorrect\soptimization\sof\scheck-in\s[e51ecadcbdef5ce6]\sas\nticket\s[5c4e7aa793943803]\sreports\sa\scase\swhere\sthe\soptimization\sdoes\snot\nwork.
- D 2020-09-30T17:32:22.269
 -C For\sthe\sOP_SeekScan\sopcode,\sadjust\sthe\snumber\sof\ssteps\srun\sbefore\sgiving\nup\sbased\son\sthe\sestimated\snumber\sof\scomparisons\sneeded\sto\sperform\sa\sseek.
 -D 2020-09-30T18:03:22.696
++C Improved\squery\soptimization\sfor\smulti-column\sindexes\swhere\sthe\ssecond\sor\nlater\scolumns\sare\sconstrained\sby\san\sIN\soperator\sand\sthe\searlier\sindex\scolumns\nlimit\sthe\ssearch\sto\sa\ssmall\snumber\sof\srows.\s\sUse\sthe\snew\sOP_SeekScan\sopcode\nwhich\sdoes\sscanning\sof\sthe\srelevant\srange\sof\sthe\sindex\sbut\sgives\sup\sand\nfalls\sback\sto\sdoing\sa\sseek\sif\sthe\snumber\sof\srows\sscanned\sgrows\sto\slarge,\nin\sorder\sto\sguard\sagainst\spathological\scases\swhere\sthe\sestimated\snumber\nof\srows\sto\sbe\sscanned\sis\sfar\stoo\ssmall.
++D 2020-09-30T18:06:51.119
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -476,8 -476,8 +476,8 @@@ F src/auth.c a3d5bfdba83d25abed1013a8c7
  F src/backup.c 3014889fa06e20e6adfa0d07b60097eec1f6e5b06671625f476a714d2356513d
  F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
  F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
- F src/btree.c 1fbb15cf6af2ccd4bc784f52bda7e6a860e303d677587b6a4b95d72ae36480a0
+ F src/btree.c c678de5bf6f57933e0ad40578fbdb0fc8113b414bf517e0a2525cb319c379874
 -F src/btree.h c64f1439377e2edf31f7c3a562586a96b71f8d0ca47e65756e7d122fd8f06928
 +F src/btree.h dcdff4037d75b3f032a5de0d922fcfaf35d48589417f634fa8627362709315f9
  F src/btreeInt.h ffd66480520d9d70222171b3a026d78b80833b5cea49c89867949f3e023d5f43
  F src/build.c 55faabe78044063eae7d1cb3767afa1bafd6edc41d950b6e2228abf601f87912
  F src/callback.c d0b853dd413255d2e337b34545e54d888ea02f20da5ad0e63585b389624c4a6c
@@@ -622,9 -622,9 +622,9 @@@ F src/vxworks.h d2988f4e5a61a4dfe82c652
  F src/wal.c 69e770e96fd56cc21608992bf2c6f1f3dc5cf2572d0495c6a643b06c3a679f14
  F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
  F src/walker.c 3df26a33dc4f54e8771600fb7fdebe1ece0896c2ad68c30ab40b017aa4395049
- F src/where.c 7ed6512e73e679231ebdeba470055e8d8e871a020b7f3f8dc75e993aaebdcbcd
- F src/whereInt.h db7472b6eb617b5853ae74bbd755383e2275be72ae03ff07cc8ea141bb146dc8
- F src/wherecode.c 13a212b333b53ded7732f6497fbb3cd01b57dc864baa9b43fbf12f13c31ce02c
+ F src/where.c da9c0d503f81cc8444eb3525b75eec2bb3d198f4d5939b207977f2fc20d85b54
+ F src/whereInt.h 59077fbd0b3d01bc8715e746c86a99ebf4c85bde8a57077ec04d2a23e59666ec
 -F src/wherecode.c ccaedd1965710e9ae35beaea59ac0ae08eb3562ab33b3a4190624b62a2e73338
++F src/wherecode.c b6293c637ecfbf2f53ae4d454cc3543f671111b3018ecc30c7bc2b3007de3782
  F src/whereexpr.c 2a05552e808047a93845278c98c6ca64a265fa8e9ffd087c161bb11bfe339866
  F src/window.c edd6f5e25a1e8f2b6f5305b7f5f7da7bb35f07f0d432b255b1d4c2fcab4205aa
  F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
@@@ -1880,8 -1880,7 +1880,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
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++Z bbfb93b0824db2f472432135890f2a72

diff --cc manifest.uuid
index 9cb067398daeefb39d9792ee5d34453069683f07,42e169af85d3aeda54f00a9b09ac0cd12245672f..245640b3fdf7253dfe0c741d9843539ca2668693
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 7395e96b8cc370c8ac2657fb805915b0992a15d80f8bf256d277b423fec64675
 -dc4172e6b8e1f62dc7329a3adb2223f290bc4c8055c265e88182ef432f4bcf10
++4a43430fd23f88352c33b29c4c105b72f6dc821f94bf362040c41a1648c402e5

diff --cc src/wherecode.c
Simple merge