Make more aggressive use of automatic indexes when processing materalized

views and subqueries.

FossilOrigin-Name: 172f5bd27e47cbdaaab54fe4383a5ee505d285257af6153ed626d9493a4adab3

manifest

@@ -1,5 +1,5 @@
-C Convert\sthe\sschema\screation\slogic\sin\sthe\srtree\sextension\sto\suse\sthe\nnew\ssqlite3_str\sinterface.
-D 2018-05-14T15:26:05.642
+C Make\smore\saggressive\suse\sof\sautomatic\sindexes\swhen\sprocessing\smateralized\nviews\sand\ssubqueries.
+D 2018-05-14T22:46:11.640
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in bfc40f350586923e0419d2ea4b559c37ec10ee4b6e210e08c14401f8e340f0da
@@ -577,7 +577,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c aa9cffc7a2bad6b826a86c8562dd4978398720ed41cb8ee7aa9d054eb8b456a0
 F src/wal.h 8de5d2d3de0956d6f6cb48c83a4012d5f227b8fe940f3a349a4b7e85ebcb492a
 F src/walker.c da987a20d40145c0a03c07d8fefcb2ed363becc7680d0500d9c79915591f5b1f
-F src/where.c d89b1aa56a75a572cd60ad27ec0fe5958d5f98b0f4391a89c72811287be7c439
+F src/where.c 60ec752fcbe9f9e0271ac60548d159a540a1ee47a4f9fedc85e88a3d0e392dd1
 F src/whereInt.h cbae2bcd37cfebdb7812a8b188cdb19634ced2b9346470d1c270556b0c33ea53
 F src/wherecode.c 728c7f70731430ccdac807a79969873e1af6968bf1c4745dff3f9dd35f636cc8
 F src/whereexpr.c e90b2e76dcabc81edff56633bf281bc01d93b71e0c81482dc06925ce39f5844a
@@ -1728,7 +1728,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 389dc0a901b0ce54c3c773d63e5b288f6dd28b96dffc4b77861db89b275b57d6
-R 6e29d58591c6ddb3e781f9c6f4a089d0
+P fd8b8c4196d3f0f6cb129f43ebf473ada86eefdf16181fa70ceee21e1232b5e1
+R 26b23505dddaf3f904e0f57ec8d12e3b
 U drh
-Z 737947d21bd079c8c254ee52cdbee001
+Z 23fd2f5ae4c9da76677cca7468979306

manifest.uuid

@@ -1 +1 @@
-fd8b8c4196d3f0f6cb129f43ebf473ada86eefdf16181fa70ceee21e1232b5e1
+172f5bd27e47cbdaaab54fe4383a5ee505d285257af6153ed626d9493a4adab3

src/where.c

@@ -2862,14 +2862,16 @@ static int whereLoopAddBtree(
         /* TUNING: One-time cost for computing the automatic index is
         ** estimated to be X*N*log2(N) where N is the number of rows in
         ** the table being indexed and where X is 7 (LogEst=28) for normal
-        ** tables or 1.375 (LogEst=4) for views and subqueries.  The value
+        ** tables or 0.5 (LogEst=-10) for views and subqueries.  The value
         ** of X is smaller for views and subqueries so that the query planner
         ** will be more aggressive about generating automatic indexes for
         ** those objects, since there is no opportunity to add schema
         ** indexes on subqueries and views. */
-        pNew->rSetup = rLogSize + rSize + 4;
+        pNew->rSetup = rLogSize + rSize;
         if( pTab->pSelect==0 && (pTab->tabFlags & TF_Ephemeral)==0 ){
-          pNew->rSetup += 24;
+          pNew->rSetup += 28;
+        }else{
+          pNew->rSetup -= 10;
         }
         ApplyCostMultiplier(pNew->rSetup, pTab->costMult);
         if( pNew->rSetup<0 ) pNew->rSetup = 0;
@@ -4005,12 +4007,15 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
 
         if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
         if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
-        if( (pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 && pFrom->nRow<10 ){
+        if( (pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 && pFrom->nRow<3 ){
           /* Do not use an automatic index if the this loop is expected
-          ** to run less than 2 times. */
+          ** to run less than 1.25 times.  It is tempting to also exclude
+          ** automatic index usage on an outer loop, but sometimes an automatic
+          ** index is useful in the outer loop of a correlated subquery. */
           assert( 10==sqlite3LogEst(2) );
           continue;
         }
+
         /* At this point, pWLoop is a candidate to be the next loop. 
         ** Compute its cost */
         rUnsorted = sqlite3LogEstAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);