Performance optimization for the sqlite3FindTable() subroutine.

FossilOrigin-Name: 55910b9a7287be92af9f95e0af54af822055d15b7eabbcc81d61410d0bf67726

manifest

@@ -1,5 +1,5 @@
-C The\sOP_RealAffinity\sopcode\sis\snot\snecessary\safter\sreading\svalues\sfrom\na\svirtual\stable\s(such\sas\srtree).\s\sIt\sis\sharmless,\sbut\sit\sdoes\suse\sCPU\ncycles.\s\sMight\sas\swell\sleave\sit\soff.
-D 2020-05-16T18:01:02.987
+C Performance\soptimization\sfor\sthe\ssqlite3FindTable()\ssubroutine.
+D 2020-05-16T21:01:00.138
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -477,7 +477,7 @@ F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
 F src/btree.c f14e415fcfd0b52b4e4ebd193ba5fadac5e8252c30f023389af682813af44025
 F src/btree.h 989ef3c33413549e3e148f3dcb46c030f317dac130dc86809ba6b9aa4b16c72a
 F src/btreeInt.h 5c8b8749805787313ecf49eb5be3ced1e94bbf8ef54bb01470ce6bd0d5185c67
-F src/build.c 520d6d125288b7da745f8299840015f66c1d1b896a9308e24d7fde6fa5fafc9b
+F src/build.c ca9e7a33b74f1bf2eb3a5f37f9d07dfed335469f2d70c0bd350e0dd42a50183a
 F src/callback.c d0b853dd413255d2e337b34545e54d888ea02f20da5ad0e63585b389624c4a6c
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c e98518d2d3d4029a13c805e07313fb60c877be56db76e90dd5f3af73085d0ce6
@@ -1866,7 +1866,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0d69f76f0865f9626078bee087a22fb826407279e78cf9d5382e1c985c9f64a9
-R 038aaeab4f18be62314e9be676a83d68
+P dc18d89354cffcb726722c234a0271ab628a71277b22887eea2bf118028193a6
+R 19171e788e643226a8c2486a995489b0
 U drh
-Z f53eca45dfc23be88eb50db1df821f15
+Z 994ffac4ccc32781ab809d359e7c6892

manifest.uuid

@@ -1 +1 @@
-dc18d89354cffcb726722c234a0271ab628a71277b22887eea2bf118028193a6
+55910b9a7287be92af9f95e0af54af822055d15b7eabbcc81d61410d0bf67726

src/build.c

@@ -312,22 +312,39 @@ Table *sqlite3FindTable(sqlite3 *db, const char *zName, const char *zDatabase){
     return 0;
   }
 #endif
-  while(1){
-    for(i=OMIT_TEMPDB; i<db->nDb; i++){
-      int j = (i<2) ? i^1 : i;   /* Search TEMP before MAIN */
-      if( zDatabase==0 || sqlite3DbIsNamed(db, j, zDatabase) ){
-        assert( sqlite3SchemaMutexHeld(db, j, 0) );
-        p = sqlite3HashFind(&db->aDb[j].pSchema->tblHash, zName);
-        if( p ) return p;
+  if( zDatabase ){
+    for(i=0; i<db->nDb; i++){
+      if( sqlite3StrICmp(zDatabase, db->aDb[i].zDbSName)==0 ) break;
+    }
+    if( i>=db->nDb ){
+      /* No match against the official names.  But always match "main"
+      ** to schema 0 as a legacy fallback. */
+      if( sqlite3StrICmp(zDatabase,"main")==0 ){
+        i = 0;
+      }else{
+        return 0;
       }
     }
-    /* Not found.  If the name we were looking for was temp.sqlite_master
-    ** then change the name to sqlite_temp_master and try again. */
-    if( sqlite3StrICmp(zName, MASTER_NAME)!=0 ) break;
-    if( sqlite3_stricmp(zDatabase, db->aDb[1].zDbSName)!=0 ) break;
-    zName = TEMP_MASTER_NAME;
+    p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
+    if( p==0 && i==1 && sqlite3StrICmp(zName, MASTER_NAME)==0 ){
+      /* All temp.sqlite_master to be an alias for sqlite_temp_master */
+      p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash, TEMP_MASTER_NAME);
+    }
+  }else{
+    /* Match against TEMP first */
+    p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash, zName);
+    if( p ) return p;
+    /* The main database is second */
+    p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, zName);
+    if( p ) return p;
+    /* Attached databases are in order of attachment */
+    for(i=2; i<db->nDb; i++){
+      assert( sqlite3SchemaMutexHeld(db, i, 0) );
+      p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
+      if( p ) break;
+    }
   }
-  return 0;
+  return p;
 }
 
 /*