Index: src/pager.c
==================================================================
--- src/pager.c
+++ src/pager.c
@@ -16,11 +16,11 @@
 ** is separate from the database file.  The pager also implements file
 ** locking to prevent two processes from writing the same database
 ** file simultaneously, or one process from reading the database while
 ** another is writing.
 **
-** @(#) $Id: pager.c,v 1.480 2008/08/26 18:05:48 danielk1977 Exp $
+** @(#) $Id: pager.c,v 1.481 2008/08/26 21:07:27 drh Exp $
 */
 #ifndef SQLITE_OMIT_DISKIO
 #include "sqliteInt.h"
 
 /*
@@ -1943,19 +1943,20 @@
 int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize){
   int rc = SQLITE_OK;
   u16 pageSize = *pPageSize;
   assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
   if( pageSize && pageSize!=pPager->pageSize 
-   && !pPager->memDb && sqlite3PcacheRefCount(pPager->pPCache)==0 
+   && (pPager->memDb==0 || pPager->dbSize==0)
+   && sqlite3PcacheRefCount(pPager->pPCache)==0 
   ){
     char *pNew = (char *)sqlite3PageMalloc(pageSize);
     if( !pNew ){
       rc = SQLITE_NOMEM;
     }else{
       pager_reset(pPager);
       pPager->pageSize = pageSize;
-      setSectorSize(pPager);
+      if( !pPager->memDb ) setSectorSize(pPager);
       sqlite3PageFree(pPager->pTmpSpace);
       pPager->pTmpSpace = pNew;
       sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
     }
   }
@@ -3570,11 +3571,15 @@
 /*
 ** Sync the pager file to disk.
 */
 int sqlite3PagerSync(Pager *pPager){
   int rc;
-  rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
+  if( MEMDB ){
+    rc = SQLITE_OK;
+  }else{
+    rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
+  }
   return rc;
 }
 
 /*
 ** Sync the database file for the pager pPager. zMaster points to the name

Index: src/vacuum.c
==================================================================
--- src/vacuum.c
+++ src/vacuum.c
@@ -12,11 +12,11 @@
 ** This file contains code used to implement the VACUUM command.
 **
 ** Most of the code in this file may be omitted by defining the
 ** SQLITE_OMIT_VACUUM macro.
 **
-** $Id: vacuum.c,v 1.82 2008/08/23 16:17:56 danielk1977 Exp $
+** $Id: vacuum.c,v 1.83 2008/08/26 21:07:27 drh Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
 
 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
@@ -79,16 +79,18 @@
 ** This routine implements the OP_Vacuum opcode of the VDBE.
 */
 int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){
   int rc = SQLITE_OK;     /* Return code from service routines */
   Btree *pMain;           /* The database being vacuumed */
+  Pager *pMainPager;      /* Pager for database being vacuumed */
   Btree *pTemp;           /* The temporary database we vacuum into */
   char *zSql = 0;         /* SQL statements */
   int saved_flags;        /* Saved value of the db->flags */
   int saved_nChange;      /* Saved value of db->nChange */
   int saved_nTotalChange; /* Saved value of db->nTotalChange */
   Db *pDb = 0;            /* Database to detach at end of vacuum */
+  int isMemDb;            /* True is vacuuming a :memory: database */
   int nRes;
 
   /* Save the current value of the write-schema flag before setting it. */
   saved_flags = db->flags;
   saved_nChange = db->nChange;
@@ -99,10 +101,12 @@
     sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
     rc = SQLITE_ERROR;
     goto end_of_vacuum;
   }
   pMain = db->aDb[0].pBt;
+  pMainPager = sqlite3BtreePager(pMain);
+  isMemDb = sqlite3PagerFile(pMainPager)->pMethods==0;
 
   /* Attach the temporary database as 'vacuum_db'. The synchronous pragma
   ** can be set to 'off' for this file, as it is not recovered if a crash
   ** occurs anyway. The integrity of the database is maintained by a
   ** (possibly synchronous) transaction opened on the main database before
@@ -135,11 +139,11 @@
     if( nKey ) db->nextPagesize = 0;
   }
 #endif
 
   if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes)
-   || sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes)
+   || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes))
    || db->mallocFailed 
   ){
     rc = SQLITE_NOMEM;
     goto end_of_vacuum;
   }

Index: test/pagesize.test
==================================================================
--- test/pagesize.test
+++ test/pagesize.test
@@ -9,11 +9,11 @@
 #
 #***********************************************************************
 # This file implements regression tests for SQLite library.
 # This file implements tests for the page_size PRAGMA.
 #
-# $Id: pagesize.test,v 1.12 2007/04/06 21:42:22 drh Exp $
+# $Id: pagesize.test,v 1.13 2008/08/26 21:07:27 drh Exp $
 
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
@@ -77,16 +77,27 @@
 }  
 foreach PGSZ {512 2048 4096 8192} {
   if {[info exists SQLITE_MAX_PAGE_SIZE]
            && $SQLITE_MAX_PAGE_SIZE<$PGSZ} continue
   ifcapable memorydb {
-    do_test pagesize-2.$PGSZ.0 {
+    do_test pagesize-2.$PGSZ.0.1 {
       db close
       sqlite3 db :memory:
       execsql "PRAGMA page_size=$PGSZ;"
       execsql {PRAGMA page_size}
-    } 1024
+    } $PGSZ
+    do_test pagesize-2.$PGSZ.0.2 {
+      execsql {CREATE TABLE t1(x UNIQUE, y UNIQUE, z UNIQUE)}
+      execsql {PRAGMA page_size}
+    } $PGSZ
+    do_test pagesize-2.$PGSZ.0.3 {
+      execsql {
+        INSERT INTO t1 VALUES(1,2,3);
+        INSERT INTO t1 VALUES(2,3,4);
+        SELECT * FROM t1;
+      }
+    } {1 2 3 2 3 4}
   }
   do_test pagesize-2.$PGSZ.1 {
     db close
     file delete -force test.db
     sqlite3 db test.db

Index: test/vacuum3.test
==================================================================
--- test/vacuum3.test
+++ test/vacuum3.test
@@ -10,11 +10,11 @@
 #***********************************************************************
 # This file implements regression tests for SQLite library.  The
 # focus of this file is changing the database page size using a 
 # VACUUM statement.
 #
-# $Id: vacuum3.test,v 1.8 2008/08/23 16:17:56 danielk1977 Exp $
+# $Id: vacuum3.test,v 1.9 2008/08/26 21:07:27 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 # If the VACUUM statement is disabled in the current build, skip all
@@ -233,11 +233,27 @@
     VACUUM;
   }
   execsql { SELECT * FROM abc } db2
 } {1 2 3 4 5 6}
 
+# Unable to change the page-size of an in-memory using vacuum.
 db2 close
+sqlite3 db2 :memory:
+do_test vacuum3-5.1 {
+  db2 eval {
+    CREATE TABLE t1(x);
+    INSERT INTO t1 VALUES(1234);
+    PRAGMA page_size=4096;
+    VACUUM;
+    SELECT * FROM t1;
+  }
+} {1234}
+do_test vacuum3-5.2 {
+  db2 eval {
+    PRAGMA page_size
+  }
+} {1024}
 
 set create_database_sql {
   BEGIN; 
   CREATE TABLE t1(a, b, c); 
   INSERT INTO t1 VALUES(1, randstr(50,50), randstr(50,50));