Change the internal btree routine moveToRoot() to return SQLITE_EMPTY if

the table is empty or if it has pgnoRoot==0.  This simplifies the callers,
making them smaller and faster.  The SQLITE_EMPTY result code is intercepted
and changed into SQLITE_OK before surfacing in an API.

FossilOrigin-Name: 240d57143d943eaddd5f7c2d473f47a1d29417e61d28142f70f3d960bb9b30df

diff --git a/manifest b/manifest
index 79eb7f408ebf93c57314833d828853bdb6c98b1b..df3d92278ac9ebc9ea743abede873ae94767c5f3 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sharmless\sindentation\serror.
-D 2017-08-14T17:03:58.073
+C Change\sthe\sinternal\sbtree\sroutine\smoveToRoot()\sto\sreturn\sSQLITE_EMPTY\sif\nthe\stable\sis\sempty\sor\sif\sit\shas\spgnoRoot==0.\s\sThis\ssimplifies\sthe\scallers,\nmaking\sthem\ssmaller\sand\sfaster.\s\sThe\sSQLITE_EMPTY\sresult\scode\sis\sintercepted\nand\schanged\sinto\sSQLITE_OK\sbefore\ssurfacing\sin\san\sAPI.
+D 2017-08-14T18:13:52.027
 F Makefile.in d9873c9925917cca9990ee24be17eb9613a668012c85a343aef7e5536ae266e8
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 02b469e9dcd5b7ee63fc1fb05babc174260ee4cfa4e0ef2e48c3c6801567a016
@@ -397,7 +397,7 @@ F src/auth.c 79f96c6f33bf0e5da8d1c282cee5ebb1852bb8a6ccca3e485d7c459b035d9c3c
 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
-F src/btree.c 5a6efa29cc6b78f3151a64424bd2f3c28e0158019c45786635ef5ff79d94e850
+F src/btree.c 43d1c5b335984abd3f9d38e87305bb0da63a638d29ea35744aabad2ddbf9fa4d
 F src/btree.h 3edc5329bc59534d2d15b4f069a9f54b779a7e51289e98fa481ae3c0e526a5ca
 F src/btreeInt.h 97700795edf8a43245720414798b7b29d8e465aef46bf301ffacd431910c0da1
 F src/build.c f8a85d2ad14c2201e10c2fe7185e1cb3f1db8b0c90d40d1fb99c20b135ab71bc
@@ -457,7 +457,7 @@ F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
 F src/select.c c9b3d8444bbf6f167d84f41ca6f3672e2521cb163a8c706b19058dc82fffe9b8
 F src/shell.c bd6a37cbe8bf64ef6a6a74fdc50f067d3148149b4ce2b4d03154663e66ded55f
 F src/shell.c.in b5725acacba95ccefa57b6d068f710e29ba8239c3aa704628a1902a1f729c175
-F src/sqlite.h.in 72f1775c7a134f9e358eedafe1ebc703c28b0d705d976464ddbf6a9219448952
+F src/sqlite.h.in f0bd1abf5e27bd22b3bcaae2a861c1efc4ab7e752bf7eb102355135617eb8199
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h a1fd3aa82f967da436164e0728a7d6841651fd0c6e27b9044e0eb9f6c8462e47
 F src/sqliteInt.h 854a122ff0ebde410a66d4f967e9923de9002f73965c6c9fa0db544bf7e657d1
@@ -1647,7 +1647,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P d0da791ba0edfb65186459345e43500d8364a086a5a1651d828fecc1a1dd1edb
-R 94ae43f22349d16aa74bde77a321d195
+P 25e92baaaeb9e8a2650b3083d3febf3661ecf1e05d9d24b26fe9f87a03bdd8fa
+R 842146c033a5d3f4b14318bddfc60ebc
 U drh
-Z ebdb69ac8faf71033c2cac4a21de62a6
+Z 43daddc7888a0248763a7ce6f2befced

diff --git a/manifest.uuid b/manifest.uuid
index a86a3b694332cd70c5c2c73b1a930201d12bf152..2c60456962c316eeb41701052a995f9631ccb310 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-25e92baaaeb9e8a2650b3083d3febf3661ecf1e05d9d24b26fe9f87a03bdd8fa
\ No newline at end of file
+240d57143d943eaddd5f7c2d473f47a1d29417e61d28142f70f3d960bb9b30df
\ No newline at end of file

diff --git a/src/btree.c b/src/btree.c
index 6602b3395b58f36b49131436245408309b8593b8..c1f8cd93645a869dc90ba6a29ab9edba66ef88e0 100644 (file)
--- a/src/btree.c
+++ b/src/btree.c
@@ -4914,9 +4914,9 @@ static void moveToParent(BtCursor *pCur){
 ** single child page. This can only happen with the table rooted at page 1.
 **
 ** If the b-tree structure is empty, the cursor state is set to 
-** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
-** cell located on the root (or virtual root) page and the cursor state
-** is set to CURSOR_VALID.
+** CURSOR_INVALID and this routine returns SQLITE_EMPTY. Otherwise,
+** the cursor is set to point to the first cell located on the root
+** (or virtual root) page and the cursor state is set to CURSOR_VALID.
 **
 ** If this function returns successfully, it may be assumed that the
 ** page-header flags indicate that the [virtual] root-page is the expected 
@@ -4935,6 +4935,7 @@ static int moveToRoot(BtCursor *pCur){
   assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
   assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
   assert( pCur->eState < CURSOR_REQUIRESEEK || pCur->iPage<0 );
+  assert( pCur->pgnoRoot>0 || pCur->iPage<0 );
 
   if( pCur->iPage>=0 ){
     if( pCur->iPage ){
@@ -4946,7 +4947,7 @@ static int moveToRoot(BtCursor *pCur){
     }
   }else if( pCur->pgnoRoot==0 ){
     pCur->eState = CURSOR_INVALID;
-    return SQLITE_OK;
+    return SQLITE_EMPTY;
   }else{
     assert( pCur->iPage==(-1) );
     if( pCur->eState>=CURSOR_REQUIRESEEK ){
@@ -4999,6 +5000,7 @@ skip_init:
     rc = moveToChild(pCur, subpage);
   }else{
     pCur->eState = CURSOR_INVALID;
+    rc = SQLITE_EMPTY;
   }
   return rc;
 }
@@ -5065,14 +5067,13 @@ int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
   assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
   rc = moveToRoot(pCur);
   if( rc==SQLITE_OK ){
-    if( pCur->eState==CURSOR_INVALID ){
-      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
-      *pRes = 1;
-    }else{
-      assert( pCur->apPage[pCur->iPage]->nCell>0 );
-      *pRes = 0;
-      rc = moveToLeftmost(pCur);
-    }
+    assert( pCur->apPage[pCur->iPage]->nCell>0 );
+    *pRes = 0;
+    rc = moveToLeftmost(pCur);
+  }else if( rc==SQLITE_EMPTY ){
+    assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
+    *pRes = 1;
+    rc = SQLITE_OK;
   }
   return rc;
 }
@@ -5104,20 +5105,18 @@ int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
 
   rc = moveToRoot(pCur);
   if( rc==SQLITE_OK ){
-    if( CURSOR_INVALID==pCur->eState ){
-      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
-      *pRes = 1;
+    assert( pCur->eState==CURSOR_VALID );
+    *pRes = 0;
+    rc = moveToRightmost(pCur);
+    if( rc==SQLITE_OK ){
+      pCur->curFlags |= BTCF_AtLast;
     }else{
-      assert( pCur->eState==CURSOR_VALID );
-      *pRes = 0;
-      rc = moveToRightmost(pCur);
-      if( rc==SQLITE_OK ){
-        pCur->curFlags |= BTCF_AtLast;
-      }else{
-        pCur->curFlags &= ~BTCF_AtLast;
-      }
-   
+      pCur->curFlags &= ~BTCF_AtLast;
     }
+  }else if( rc==SQLITE_EMPTY ){
+    assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
+    *pRes = 1;
+    rc = SQLITE_OK;
   }
   return rc;
 }
@@ -5216,16 +5215,17 @@ int sqlite3BtreeMovetoUnpacked(
 
   rc = moveToRoot(pCur);
   if( rc ){
+    if( rc==SQLITE_EMPTY ){
+      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
+      *pRes = -1;
+      return SQLITE_OK;
+    }
     return rc;
   }
-  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage] );
-  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->isInit );
-  assert( pCur->eState==CURSOR_INVALID || pCur->apPage[pCur->iPage]->nCell>0 );
-  if( pCur->eState==CURSOR_INVALID ){
-    *pRes = -1;
-    assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
-    return SQLITE_OK;
-  }
+  assert( pCur->apPage[pCur->iPage] );
+  assert( pCur->apPage[pCur->iPage]->isInit );
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->apPage[pCur->iPage]->nCell > 0 );
   assert( pCur->apPage[0]->intKey==pCur->curIntKey );
   assert( pCur->curIntKey || pIdxKey );
   for(;;){
@@ -8439,6 +8439,7 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
         btreeReleaseAllCursorPages(pCur);
         pCur->eState = CURSOR_REQUIRESEEK;
       }
+      if( rc==SQLITE_EMPTY ) rc = SQLITE_OK;
     }
   }
   return rc;
@@ -8903,11 +8904,11 @@ int sqlite3BtreeCount(BtCursor *pCur, i64 *pnEntry){
   i64 nEntry = 0;                      /* Value to return in *pnEntry */
   int rc;                              /* Return code */
 
-  if( pCur->pgnoRoot==0 ){
+  rc = moveToRoot(pCur);
+  if( rc==SQLITE_EMPTY ){
     *pnEntry = 0;
     return SQLITE_OK;
   }
-  rc = moveToRoot(pCur);
 
   /* Unless an error occurs, the following loop runs one iteration for each
   ** page in the B-Tree structure (not including overflow pages). 

diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index ad97b9a0dea7d3c5c54ad4535ea385cde05205df..1020e5f3d6e32acfd7c935d9d269ee1724aaea36 100644 (file)
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -432,7 +432,7 @@ int sqlite3_exec(
 #define SQLITE_FULL        13   /* Insertion failed because database is full */
 #define SQLITE_CANTOPEN    14   /* Unable to open the database file */
 #define SQLITE_PROTOCOL    15   /* Database lock protocol error */
-#define SQLITE_EMPTY       16   /* Not used */
+#define SQLITE_EMPTY       16   /* Internal use only */
 #define SQLITE_SCHEMA      17   /* The database schema changed */
 #define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
 #define SQLITE_CONSTRAINT  19   /* Abort due to constraint violation */