Size and performance optimization the readDbPage() routine in the pager.

FossilOrigin-Name: ca9e1875c3a893321d70a131fc4ffc76d169ad05e0b48b7006f53b6b467db4be

diff --git a/manifest b/manifest
index 78a97342e55c4d13c7b8332f7b7cc8320cea1abf..1e5d32d66bf3ed4d9a7ac80e819ed26dbfa21b9a 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C For\sthe\sunix\sVFS,\savoid\san\sunnecessary\sstat()\ssystem\scall\sprior\sto\sopening\nany\sfile\sin\sthe\scommon\scase\swhere\sthere\sare\sno\sunused\sfile\sdescriptors.
-D 2017-08-18T16:09:52.797
+C Size\sand\sperformance\soptimization\sthe\sreadDbPage()\sroutine\sin\sthe\spager.
+D 2017-08-18T21:14:50.622
 F Makefile.in d9873c9925917cca9990ee24be17eb9613a668012c85a343aef7e5536ae266e8
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 02b469e9dcd5b7ee63fc1fb05babc174260ee4cfa4e0ef2e48c3c6801567a016
@@ -443,7 +443,7 @@ F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
 F src/os_unix.c 0a7730f6cb797ba1fd12825e4ea751e1325041410c063c258e30089ca71f9a88
 F src/os_win.c 964165b66cde03abc72fe948198b01be608436894732eadb94c8720d2467f223
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c 6f2ae58c0d4ddf510d324cb2ec38f471b5cff8f3e061afd32717ad790685cc7f
+F src/pager.c fb9a8f40417d6dfbd6b8be91237f2f64d51cc867ab28687420acbc5cab786a3c
 F src/pager.h f2a99646c5533ffe11afa43e9e0bea74054e4efa
 F src/parse.y 52ef3cecd0934e9da4a45b585883a03243ad615d338ad94f44501a05891dcdfa
 F src/pcache.c 62835bed959e2914edd26afadfecce29ece0e870
@@ -1649,7 +1649,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P eb1202b5e43f1f029ad2bdf845509e7f31361e4dc189943e5e2bd4462e2ef3f3
-R 75fd277ce5c40358998ed365a587d991
+P 3075cfa07489eaf13cb9a2760e2391e79dd73181fe1730fae7bdcd6ad66d2a1f
+R 73e91e0689b3737aa34e053426722c6a
 U drh
-Z 8da9bd8ec0af0fa3e80213d960cc13a7
+Z 58f532a67b173dfa15cad7f44c1bc81c

diff --git a/manifest.uuid b/manifest.uuid
index 97cbaa15bbf0943d1a77adc474c92087c0a9668a..59813005d8efd68ba894842ab5155428ca04610c 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-3075cfa07489eaf13cb9a2760e2391e79dd73181fe1730fae7bdcd6ad66d2a1f
\ No newline at end of file
+ca9e1875c3a893321d70a131fc4ffc76d169ad05e0b48b7006f53b6b467db4be
\ No newline at end of file

diff --git a/src/pager.c b/src/pager.c
index 1677dfcda7c236ae2c780f744f697572b0bc7426..9a430476a1c77482eac0dfa93b56ea6f78b6b326 100644 (file)
--- a/src/pager.c
+++ b/src/pager.c
@@ -2982,7 +2982,8 @@ end_playback:
 
 
 /*
-** Read the content for page pPg out of the database file and into 
+** Read the content for page pPg out of the database file (or out of
+** the WAL if that is where the most recent copy if found) into 
 ** pPg->pData. A shared lock or greater must be held on the database
 ** file before this function is called.
 **
@@ -2992,22 +2993,23 @@ end_playback:
 ** If an IO error occurs, then the IO error is returned to the caller.
 ** Otherwise, SQLITE_OK is returned.
 */
-static int readDbPage(PgHdr *pPg, u32 iFrame){
+static int readDbPage(PgHdr *pPg){
   Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
   Pgno pgno = pPg->pgno;       /* Page number to read */
   int rc = SQLITE_OK;          /* Return code */
   int pgsz = pPager->pageSize; /* Number of bytes to read */
+  u32 iFrame = 0;              /* Frame of WAL containing pgno */
 
   assert( pPager->eState>=PAGER_READER && !MEMDB );
   assert( isOpen(pPager->fd) );
 
-#ifndef SQLITE_OMIT_WAL
+  if( pagerUseWal(pPager) ){
+    rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
+    if( rc ) return rc;
+  }
   if( iFrame ){
-    /* Try to pull the page from the write-ahead log. */
     rc = sqlite3WalReadFrame(pPager->pWal, iFrame, pgsz, pPg->pData);
-  }else
-#endif
-  {
+  }else{
     i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
     rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
     if( rc==SQLITE_IOERR_SHORT_READ ){
@@ -3092,11 +3094,7 @@ static int pagerUndoCallback(void *pCtx, Pgno iPg){
     if( sqlite3PcachePageRefcount(pPg)==1 ){
       sqlite3PcacheDrop(pPg);
     }else{
-      u32 iFrame = 0;
-      rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
-      if( rc==SQLITE_OK ){
-        rc = readDbPage(pPg, iFrame);
-      }
+      rc = readDbPage(pPg);
       if( rc==SQLITE_OK ){
         pPager->xReiniter(pPg);
       }
@@ -5489,14 +5487,9 @@ static int getPageNormal(
       memset(pPg->pData, 0, pPager->pageSize);
       IOTRACE(("ZERO %p %d\n", pPager, pgno));
     }else{
-      u32 iFrame = 0;                 /* Frame to read from WAL file */
-      if( pagerUseWal(pPager) ){
-        rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
-        if( rc!=SQLITE_OK ) goto pager_acquire_err;
-      }
       assert( pPg->pPager==pPager );
       pPager->aStat[PAGER_STAT_MISS]++;
-      rc = readDbPage(pPg, iFrame);
+      rc = readDbPage(pPg);
       if( rc!=SQLITE_OK ){
         goto pager_acquire_err;
       }