From: drh <drh@noemail.net>
Date: Fri, 7 Jun 2013 02:04:19 +0000 (+0000)
Subject: Must faster computation of estimated logarithm.
X-Git-Tag: version-3.8.0~130^2~16
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=23fec451a6bdb4d0b598592c66567ef7f6485330;p=thirdparty%2Fsqlite.git

Must faster computation of estimated logarithm.

FossilOrigin-Name: dfbca3acaeb862f24f25e7810a16ff2066111ff4
---

diff --git a/manifest b/manifest
index 6c3bd8a20c..d0734bd638 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Further\sprepare-time\sperformance\simprovements.
-D 2013-06-07T00:29:23.782
+C Must\sfaster\scomputation\sof\sestimated\slogarithm.
+D 2013-06-07T02:04:19.774
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 5e41da95d92656a5004b03d3576e8b226858a28e
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -289,7 +289,7 @@ F src/vtab.c b05e5f1f4902461ba9f5fc49bb7eb7c3a0741a83
 F src/wal.c 436bfceb141b9423c45119e68e444358ee0ed35d
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 4fa43583d0a84b48f93b1e88f11adf2065be4e73
-F src/where.c bbd8aad0e54692a107d0f68111a289149814b10c
+F src/where.c 70e1ebd1c3f828f4062fc2b5ada2461419020dae
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test 45c0201e28045ad38a530b5a144b73cd4aa2cfd6
@@ -1094,7 +1094,7 @@ F tool/vdbe-compress.tcl f12c884766bd14277f4fcedcae07078011717381
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
 F tool/win/sqlite.vsix 97894c2790eda7b5bce3cc79cb2a8ec2fde9b3ac
-P 9f8e84ab9874a8af826763b1669adb57abd493ea
-R 8930578735fbc55c72ec3d27796f6bd0
+P 02741d177bfc2fca23bc99974cd899eba13cb59a
+R 8ee17766ef9ac6851fd1329c34593963
 U drh
-Z c23263f2bef48916be7bbfa11913b59d
+Z adf16c6d5fc0c897d258a12782d83ad0
diff --git a/manifest.uuid b/manifest.uuid
index aaaa9ad535..8ae2ff38a7 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-02741d177bfc2fca23bc99974cd899eba13cb59a
\ No newline at end of file
+dfbca3acaeb862f24f25e7810a16ff2066111ff4
\ No newline at end of file
diff --git a/src/where.c b/src/where.c
index 3b825214f5..c1fc4301d7 100644
--- a/src/where.c
+++ b/src/where.c
@@ -1831,13 +1831,11 @@ static int isDistinctRedundant(
 ** logN is a little off.
 */
 static WhereCost estLog(WhereCost N){
-  WhereCost logN = 1;
-  WhereCost x = 10;
-  while( N>x ){
-    logN += 1;
-    x *= 10;
-  }
-  return logN;
+  u32 a;
+  assert( sizeof(WhereCost)==4 );  /* 32-bit float input */
+  if( N<=0.0 ) return 0.0;
+  memcpy(&a, &N, 4);
+  return ((a >>= 23)-127)*0.3;
 }
 
 /*
@@ -5398,6 +5396,7 @@ WhereInfo *sqlite3WhereBegin(
 
   /* Construct the WhereLoop objects */
   WHERETRACE(("*** Optimizer Start ***\n"));
+  /* TBD: if( nTablist==1 ) whereCommonCase(&sWLB); */
   rc = whereLoopAddAll(&sWLB);
   if( rc ) goto whereBeginError;