Query planner improvements: Take the LIMIT into account when estimated the

cost of an ORDER BY.  Avoid automatic indexes on query loops that are expected
to run less than twice.

FossilOrigin-Name: bf46179d4484376909dce40ffcc06fecb19b3544

diff --cc manifest
index ed34efd9187d628022e6a94b20a1c564be3a40af,cb1fddd357c5a2f9b0157b75fef559b8ce3970ae..cd7f610e12d6a17a84704ded1937d5d93e3b1c48
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C In\sthe\scommand-line\sshell:\s\sWhen\sthe\s".import"\scommand\sis\screating\sa\snew\ntable\susing\scolumn\snames\sfrom\sthe\sfirst\srow\sof\sCSV\sinput,\smake\ssure\s\ndouble-quotes\sin\sthe\sname\sare\sproperly\sescaped.
- D 2016-02-25T13:33:02.701
 -C Improvement\son\sthe\sprevious\scheck-in:\s\sdisallow\sautomatic\sindexes\sfor\sany\nloop\sthat\sis\sexpected\sto\srun\sless\sthan\stwice.
 -D 2016-02-25T18:22:09.962
++C Query\splanner\simprovements:\s\sTake\sthe\sLIMIT\sinto\saccount\swhen\sestimated\sthe\ncost\sof\san\sORDER\sBY.\s\sAvoid\sautomatic\sindexes\son\squery\sloops\sthat\sare\sexpected\nto\srun\sless\sthan\stwice.
++D 2016-02-25T18:40:18.408
  F Makefile.in 4e90dc1521879022aa9479268a4cd141d1771142
  F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
  F Makefile.msc 28fc4ee02333996d31b3602b39eeb8e609a89ce4
@@@ -1429,7 -1429,7 +1429,8 @@@ F tool/vdbe_profile.tcl 246d0da094856d7
  F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
  F tool/warnings.sh a98af506df552f3b3c0d904f94e4cdc4e1a6d598
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diff --cc manifest.uuid
index 6f30a6f9251ab8a479d69cd8385ea6c658d1258d,27e8814012eaa9b7fba254eb26aa121ff058ad32..6a068ab962b08b3e59d4fc0de45b29a4447e7705
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 2e67a1c823c7003e7d2619c7d8b6db6ce046c527
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++bf46179d4484376909dce40ffcc06fecb19b3544