Import SQLite 3.8.7.4.

third_party/sqlite/src/src/test_multiplex.c

Index: third_party/sqlite/src/src/test_multiplex.c
diff --git a/third_party/sqlite/src/src/test_multiplex.c b/third_party/sqlite/src/src/test_multiplex.c
index d8a7db86e1d4f568b3cd745b38eba105636e58dd..99819371ce5eb6b86df072b64ccac0abef29a9f3 100644
--- a/third_party/sqlite/src/src/test_multiplex.c
+++ b/third_party/sqlite/src/src/test_multiplex.c
@@ -11,17 +11,46 @@
 *************************************************************************
 **
 ** This file contains a VFS "shim" - a layer that sits in between the
-** pager and the real VFS.
+** pager and the real VFS - that breaks up a very large database file
+** into two or more smaller files on disk.  This is useful, for example,
+** in order to support large, multi-gigabyte databases on older filesystems
+** that limit the maximum file size to 2 GiB.
 **
-** This particular shim enforces a multiplex system on DB files.  
-** This shim shards/partitions a single DB file into smaller 
-** "chunks" such that the total DB file size may exceed the maximum
-** file size of the underlying file system.
+** USAGE:
 **
+** Compile this source file and link it with your application.  Then
+** at start-time, invoke the following procedure:
+**
+**   int sqlite3_multiplex_initialize(
+**      const char *zOrigVfsName,    // The underlying real VFS
+**      int makeDefault              // True to make multiplex the default VFS
+**   );
+**
+** The procedure call above will create and register a new VFS shim named
+** "multiplex".  The multiplex VFS will use the VFS named by zOrigVfsName to
+** do the actual disk I/O.  (The zOrigVfsName parameter may be NULL, in 
+** which case the default VFS at the moment sqlite3_multiplex_initialize()
+** is called will be used as the underlying real VFS.)  
+**
+** If the makeDefault parameter is TRUE then multiplex becomes the new
+** default VFS.  Otherwise, you can use the multiplex VFS by specifying
+** "multiplex" as the 4th parameter to sqlite3_open_v2() or by employing
+** URI filenames and adding "vfs=multiplex" as a parameter to the filename
+** URI.
+**
+** The multiplex VFS allows databases up to 32 GiB in size.  But it splits
+** the files up into smaller pieces, so that they will work even on 
+** filesystems that do not support large files.  The default chunk size
+** is 2147418112 bytes (which is 64KiB less than 2GiB) but this can be
+** changed at compile-time by defining the SQLITE_MULTIPLEX_CHUNK_SIZE
+** macro.  Use the "chunksize=NNNN" query parameter with a URI filename
+** in order to select an alternative chunk size for individual connections
+** at run-time.
 */
 #include "sqlite3.h"
 #include <string.h>
 #include <assert.h>
+#include <stdlib.h>
 #include "test_multiplex.h"
 
 #ifndef SQLITE_CORE
@@ -31,7 +60,7 @@
 
 /* 
 ** These should be defined to be the same as the values in 
-** sqliteInt.h.  They are defined seperately here so that
+** sqliteInt.h.  They are defined separately here so that
 ** the multiplex VFS shim can be built as a loadable 
 ** module.
 */
@@ -52,34 +81,37 @@
 #define sqlite3_mutex_notheld(X)  ((void)(X),1)
 #endif /* SQLITE_THREADSAFE==0 */
 
+/* Maximum chunk number */
+#define MX_CHUNK_NUMBER 299
+
+/* First chunk for rollback journal files */
+#define SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET 400
+#define SQLITE_MULTIPLEX_WAL_8_3_OFFSET 700
+
 
 /************************ Shim Definitions ******************************/
 
-#define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
+#ifndef SQLITE_MULTIPLEX_VFS_NAME
+# define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
+#endif
 
 /* This is the limit on the chunk size.  It may be changed by calling
 ** the xFileControl() interface.  It will be rounded up to a 
-** multiple of MAX_PAGE_SIZE.  We default it here to 1GB.
+** multiple of MAX_PAGE_SIZE.  We default it here to 2GiB less 64KiB.
 */
-#define SQLITE_MULTIPLEX_CHUNK_SIZE (MAX_PAGE_SIZE*16384)
+#ifndef SQLITE_MULTIPLEX_CHUNK_SIZE
+# define SQLITE_MULTIPLEX_CHUNK_SIZE 2147418112
+#endif
 
-/* Default limit on number of chunks.  Care should be taken
-** so that values for chunks numbers fit in the SQLITE_MULTIPLEX_EXT_FMT
-** format specifier. It may be changed by calling
-** the xFileControl() interface.
-*/
-#define SQLITE_MULTIPLEX_MAX_CHUNKS 32
-
-/* If SQLITE_MULTIPLEX_EXT_OVWR is defined, the 
-** last SQLITE_MULTIPLEX_EXT_SZ characters of the 
-** filename will be overwritten, otherwise, the 
-** multiplex extension is simply appended to the filename.
-** Ex.  (undefined) test.db -> test.db01
-**      (defined)   test.db -> test.01
-** Chunk 0 does not have a modified extension.
+/* This used to be the default limit on number of chunks, but
+** it is no longer enforced. There is currently no limit to the
+** number of chunks.
+**
+** May be changed by calling the xFileControl() interface.
 */
-#define SQLITE_MULTIPLEX_EXT_FMT    "%02d"
-#define SQLITE_MULTIPLEX_EXT_SZ     2
+#ifndef SQLITE_MULTIPLEX_MAX_CHUNKS
+# define SQLITE_MULTIPLEX_MAX_CHUNKS 12
+#endif
 
 /************************ Object Definitions ******************************/
 
@@ -96,14 +128,17 @@ typedef struct multiplexConn multiplexConn;
 ** group.
 */
 struct multiplexGroup {
-  sqlite3_file **pReal;            /* Handles to each chunk */
-  char *bOpen;                     /* array of bools - 0 if chunk not opened */
+  struct multiplexReal {           /* For each chunk */
+    sqlite3_file *p;                  /* Handle for the chunk */
+    char *z;                          /* Name of this chunk */
+  } *aReal;                        /* list of all chunks */
+  int nReal;                       /* Number of chunks */
   char *zName;                     /* Base filename of this group */
   int nName;                       /* Length of base filename */
   int flags;                       /* Flags used for original opening */
-  int nChunkSize;                  /* Chunk size used for this group */
-  int nMaxChunks;                  /* Max number of chunks for this group */
-  int bEnabled;                    /* TRUE to use Multiplex VFS for this file */
+  unsigned int szChunk;            /* Chunk size used for this group */
+  unsigned char bEnabled;          /* TRUE to use Multiplex VFS for this file */
+  unsigned char bTruncate;         /* TRUE to enable truncation of databases */
   multiplexGroup *pNext, *pPrev;   /* Doubly linked list of all group objects */
 };
 
@@ -161,12 +196,6 @@ static struct {
   /* List of multiplexGroup objects.
   */
   multiplexGroup *pGroups;
-
-  /* Storage for temp file names.  Allocated during 
-  ** initialization to the max pathname of the underlying VFS.
-  */
-  char *zName;
-
 } gMultiplex;
 
 /************************* Utility Routines *********************************/
@@ -185,45 +214,189 @@ static void multiplexLeave(void){ sqlite3_mutex_leave(gMultiplex.pMutex); }
 ** than the actual length of the string.  For very long strings (greater
 ** than 1GiB) the value returned might be less than the true string length.
 */
-int multiplexStrlen30(const char *z){
+static int multiplexStrlen30(const char *z){
   const char *z2 = z;
   if( z==0 ) return 0;
   while( *z2 ){ z2++; }
   return 0x3fffffff & (int)(z2 - z);
 }
 
+/*
+** Generate the file-name for chunk iChunk of the group with base name
+** zBase. The file-name is written to buffer zOut before returning. Buffer
+** zOut must be allocated by the caller so that it is at least (nBase+5)
+** bytes in size, where nBase is the length of zBase, not including the
+** nul-terminator.
+**
+** If iChunk is 0 (or 400 - the number for the first journal file chunk),
+** the output is a copy of the input string. Otherwise, if 
+** SQLITE_ENABLE_8_3_NAMES is not defined or the input buffer does not contain
+** a "." character, then the output is a copy of the input string with the 
+** three-digit zero-padded decimal representation if iChunk appended to it. 
+** For example:
+**
+**   zBase="test.db", iChunk=4  ->  zOut="test.db004"
+**
+** Or, if SQLITE_ENABLE_8_3_NAMES is defined and the input buffer contains
+** a "." character, then everything after the "." is replaced by the 
+** three-digit representation of iChunk.
+**
+**   zBase="test.db", iChunk=4  ->  zOut="test.004"
+**
+** The output buffer string is terminated by 2 0x00 bytes. This makes it safe
+** to pass to sqlite3_uri_parameter() and similar.
+*/
+static void multiplexFilename(
+  const char *zBase,              /* Filename for chunk 0 */
+  int nBase,                      /* Size of zBase in bytes (without \0) */
+  int flags,                      /* Flags used to open file */
+  int iChunk,                     /* Chunk to generate filename for */
+  char *zOut                      /* Buffer to write generated name to */
+){
+  int n = nBase;
+  memcpy(zOut, zBase, n+1);
+  if( iChunk!=0 && iChunk<=MX_CHUNK_NUMBER ){
+#ifdef SQLITE_ENABLE_8_3_NAMES
+    int i;
+    for(i=n-1; i>0 && i>=n-4 && zOut[i]!='.'; i--){}
+    if( i>=n-4 ) n = i+1;
+    if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
+      /* The extensions on overflow files for main databases are 001, 002,
+      ** 003 and so forth.  To avoid name collisions, add 400 to the 
+      ** extensions of journal files so that they are 401, 402, 403, ....
+      */
+      iChunk += SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET;
+    }else if( flags & SQLITE_OPEN_WAL ){
+      /* To avoid name collisions, add 700 to the 
+      ** extensions of WAL files so that they are 701, 702, 703, ....
+      */
+      iChunk += SQLITE_MULTIPLEX_WAL_8_3_OFFSET;
+    }
+#endif
+    sqlite3_snprintf(4,&zOut[n],"%03d",iChunk);
+    n += 3;
+  }
+
+  assert( zOut[n]=='\0' );
+  zOut[n+1] = '\0';
+}
+
+/* Compute the filename for the iChunk-th chunk
+*/
+static int multiplexSubFilename(multiplexGroup *pGroup, int iChunk){
+  if( iChunk>=pGroup->nReal ){
+    struct multiplexReal *p;
+    p = sqlite3_realloc(pGroup->aReal, (iChunk+1)*sizeof(*p));
+    if( p==0 ){
+      return SQLITE_NOMEM;
+    }
+    memset(&p[pGroup->nReal], 0, sizeof(p[0])*(iChunk+1-pGroup->nReal));
+    pGroup->aReal = p;
+    pGroup->nReal = iChunk+1;
+  }
+  if( pGroup->zName && pGroup->aReal[iChunk].z==0 ){
+    char *z;
+    int n = pGroup->nName;
+    pGroup->aReal[iChunk].z = z = sqlite3_malloc( n+5 );
+    if( z==0 ){
+      return SQLITE_NOMEM;
+    }
+    multiplexFilename(pGroup->zName, pGroup->nName, pGroup->flags, iChunk, z);
+  }
+  return SQLITE_OK;
+}
+
 /* Translate an sqlite3_file* that is really a multiplexGroup* into
 ** the sqlite3_file* for the underlying original VFS.
+**
+** For chunk 0, the pGroup->flags determines whether or not a new file
+** is created if it does not already exist.  For chunks 1 and higher, the
+** file is created only if createFlag is 1.
 */
-static sqlite3_file *multiplexSubOpen(multiplexConn *pConn, int iChunk, int *rc, int *pOutFlags){
-  multiplexGroup *pGroup = pConn->pGroup;
+static sqlite3_file *multiplexSubOpen(
+  multiplexGroup *pGroup,    /* The multiplexor group */
+  int iChunk,                /* Which chunk to open.  0==original file */
+  int *rc,                   /* Result code in and out */
+  int *pOutFlags,            /* Output flags */
+  int createFlag             /* True to create if iChunk>0 */
+){
+  sqlite3_file *pSubOpen = 0;
   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;        /* Real VFS */
-  if( iChunk<pGroup->nMaxChunks ){
-    sqlite3_file *pSubOpen = pGroup->pReal[iChunk];    /* Real file descriptor */
-    if( !pGroup->bOpen[iChunk] ){
-      memcpy(gMultiplex.zName, pGroup->zName, pGroup->nName+1);
-      if( iChunk ){
-#ifdef SQLITE_MULTIPLEX_EXT_OVWR
-        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, gMultiplex.zName+pGroup->nName-SQLITE_MULTIPLEX_EXT_SZ, SQLITE_MULTIPLEX_EXT_FMT, iChunk);
-#else
-        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, gMultiplex.zName+pGroup->nName, SQLITE_MULTIPLEX_EXT_FMT, iChunk);
+
+#ifdef SQLITE_ENABLE_8_3_NAMES
+  /* If JOURNAL_8_3_OFFSET is set to (say) 400, then any overflow files are 
+  ** part of a database journal are named db.401, db.402, and so on. A 
+  ** database may therefore not grow to larger than 400 chunks. Attempting
+  ** to open chunk 401 indicates the database is full. */
+  if( iChunk>=SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET ){
+    sqlite3_log(SQLITE_FULL, "multiplexed chunk overflow: %s", pGroup->zName);
+    *rc = SQLITE_FULL;
+    return 0;
+  }
 #endif
+
+  *rc = multiplexSubFilename(pGroup, iChunk);
+  if( (*rc)==SQLITE_OK && (pSubOpen = pGroup->aReal[iChunk].p)==0 ){
+    int flags, bExists;
+    flags = pGroup->flags;
+    if( createFlag ){
+      flags |= SQLITE_OPEN_CREATE;
+    }else if( iChunk==0 ){
+      /* Fall through */
+    }else if( pGroup->aReal[iChunk].z==0 ){
+      return 0;
+    }else{
+      *rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[iChunk].z,
+                              SQLITE_ACCESS_EXISTS, &bExists);
+     if( *rc || !bExists ){
+        if( *rc ){
+          sqlite3_log(*rc, "multiplexor.xAccess failure on %s",
+                      pGroup->aReal[iChunk].z);
+        }
+        return 0;
       }
-      *rc = pOrigVfs->xOpen(pOrigVfs, gMultiplex.zName, pSubOpen, pGroup->flags, pOutFlags);
-      if( *rc==SQLITE_OK ){
-        pGroup->bOpen[iChunk] = -1;
-        return pSubOpen;
-      }
-      return NULL;
+      flags &= ~SQLITE_OPEN_CREATE;
+    }
+    pSubOpen = sqlite3_malloc( pOrigVfs->szOsFile );
+    if( pSubOpen==0 ){
+      *rc = SQLITE_IOERR_NOMEM;
+      return 0;
+    }
+    pGroup->aReal[iChunk].p = pSubOpen;
+    *rc = pOrigVfs->xOpen(pOrigVfs, pGroup->aReal[iChunk].z, pSubOpen,
+                          flags, pOutFlags);
+    if( (*rc)!=SQLITE_OK ){
+      sqlite3_log(*rc, "multiplexor.xOpen failure on %s",
+                  pGroup->aReal[iChunk].z);
+      sqlite3_free(pSubOpen);
+      pGroup->aReal[iChunk].p = 0;
+      return 0;
     }
-    *rc = SQLITE_OK;
-    return pSubOpen;
   }
-  *rc = SQLITE_FULL;
-  return NULL;
+  return pSubOpen;
 }
 
 /*
+** Return the size, in bytes, of chunk number iChunk.  If that chunk
+** does not exist, then return 0.  This function does not distingish between
+** non-existant files and zero-length files.
+*/
+static sqlite3_int64 multiplexSubSize(
+  multiplexGroup *pGroup,    /* The multiplexor group */
+  int iChunk,                /* Which chunk to open.  0==original file */
+  int *rc                    /* Result code in and out */
+){
+  sqlite3_file *pSub;
+  sqlite3_int64 sz = 0;
+
+  if( *rc ) return 0;
+  pSub = multiplexSubOpen(pGroup, iChunk, rc, NULL, 0);
+  if( pSub==0 ) return 0;
+  *rc = pSub->pMethods->xFileSize(pSub, &sz);
+  return sz;
+}    
+
+/*
 ** This is the implementation of the multiplex_control() SQL function.
 */
 static void multiplexControlFunc(
@@ -279,6 +452,38 @@ static int multiplexFuncInit(
   return rc;
 }
 
+/*
+** Close a single sub-file in the connection group.
+*/
+static void multiplexSubClose(
+  multiplexGroup *pGroup,
+  int iChunk,
+  sqlite3_vfs *pOrigVfs
+){
+  sqlite3_file *pSubOpen = pGroup->aReal[iChunk].p;
+  if( pSubOpen ){
+    pSubOpen->pMethods->xClose(pSubOpen);
+    if( pOrigVfs && pGroup->aReal[iChunk].z ){
+      pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
+    }
+    sqlite3_free(pGroup->aReal[iChunk].p);
+  }
+  sqlite3_free(pGroup->aReal[iChunk].z);
+  memset(&pGroup->aReal[iChunk], 0, sizeof(pGroup->aReal[iChunk]));
+}
+
+/*
+** Deallocate memory held by a multiplexGroup
+*/
+static void multiplexFreeComponents(multiplexGroup *pGroup){
+  int i;
+  for(i=0; i<pGroup->nReal; i++){ multiplexSubClose(pGroup, i, 0); }
+  sqlite3_free(pGroup->aReal);
+  pGroup->aReal = 0;
+  pGroup->nReal = 0;
+}
+
+
 /************************* VFS Method Wrappers *****************************/
 
 /*
@@ -295,70 +500,121 @@ static int multiplexOpen(
   int flags,                 /* Flags to control the opening */
   int *pOutFlags             /* Flags showing results of opening */
 ){
-  int rc;                                        /* Result code */
-  multiplexConn *pMultiplexOpen;                 /* The new multiplex file descriptor */
-  multiplexGroup *pGroup;                        /* Corresponding multiplexGroup object */
-  sqlite3_file *pSubOpen;                        /* Real file descriptor */
+  int rc = SQLITE_OK;                  /* Result code */
+  multiplexConn *pMultiplexOpen;       /* The new multiplex file descriptor */
+  multiplexGroup *pGroup = 0;          /* Corresponding multiplexGroup object */
+  sqlite3_file *pSubOpen = 0;                    /* Real file descriptor */
   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
-  int nName = multiplexStrlen30(zName);
-  int i;
-  int sz;
+  int nName = 0;
+  int sz = 0;
+  char *zToFree = 0;
 
   UNUSED_PARAMETER(pVfs);
+  memset(pConn, 0, pVfs->szOsFile);
+  assert( zName || (flags & SQLITE_OPEN_DELETEONCLOSE) );
 
   /* We need to create a group structure and manage
   ** access to this group of files.
   */
   multiplexEnter();
   pMultiplexOpen = (multiplexConn*)pConn;
-  /* allocate space for group */
-  sz = sizeof(multiplexGroup)                                /* multiplexGroup */
-     + (sizeof(sqlite3_file *)*SQLITE_MULTIPLEX_MAX_CHUNKS)  /* pReal[] */
-     + (pOrigVfs->szOsFile*SQLITE_MULTIPLEX_MAX_CHUNKS)      /* *pReal */
-     + SQLITE_MULTIPLEX_MAX_CHUNKS                           /* bOpen[] */
-     + nName + 1;                                            /* zName */
-#ifndef SQLITE_MULTIPLEX_EXT_OVWR
-  sz += SQLITE_MULTIPLEX_EXT_SZ;
-  assert(nName+SQLITE_MULTIPLEX_EXT_SZ < pOrigVfs->mxPathname);
-#else
-  assert(nName >= SQLITE_MULTIPLEX_EXT_SZ);
-  assert(nName < pOrigVfs->mxPathname);
-#endif
-  pGroup = sqlite3_malloc( sz );
-  if( pGroup==0 ){
-    rc=SQLITE_NOMEM;
-  }else{
+
+  if( rc==SQLITE_OK ){
+    /* allocate space for group */
+    nName = zName ? multiplexStrlen30(zName) : 0;
+    sz = sizeof(multiplexGroup)                             /* multiplexGroup */
+       + nName + 1;                                         /* zName */
+    pGroup = sqlite3_malloc( sz );
+    if( pGroup==0 ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    const char *zUri = (flags & SQLITE_OPEN_URI) ? zName : 0;
     /* assign pointers to extra space allocated */
-    char *p = (char *)&pGroup[1];
-    pMultiplexOpen->pGroup = pGroup;
     memset(pGroup, 0, sz);
+    pMultiplexOpen->pGroup = pGroup;
     pGroup->bEnabled = -1;
-    pGroup->nChunkSize = SQLITE_MULTIPLEX_CHUNK_SIZE;
-    pGroup->nMaxChunks = SQLITE_MULTIPLEX_MAX_CHUNKS;
-    pGroup->pReal = (sqlite3_file **)p;
-    p += (sizeof(sqlite3_file *)*pGroup->nMaxChunks);
-    for(i=0; i<pGroup->nMaxChunks; i++){
-      pGroup->pReal[i] = (sqlite3_file *)p;
-      p += pOrigVfs->szOsFile;
+    pGroup->bTruncate = sqlite3_uri_boolean(zUri, "truncate", 
+                                   (flags & SQLITE_OPEN_MAIN_DB)==0);
+    pGroup->szChunk = (int)sqlite3_uri_int64(zUri, "chunksize",
+                                        SQLITE_MULTIPLEX_CHUNK_SIZE);
+    pGroup->szChunk = (pGroup->szChunk+0xffff)&~0xffff;
+    if( zName ){
+      char *p = (char *)&pGroup[1];
+      pGroup->zName = p;
+      memcpy(pGroup->zName, zName, nName+1);
+      pGroup->nName = nName;
+    }
+    if( pGroup->bEnabled ){
+      /* Make sure that the chunksize is such that the pending byte does not
+      ** falls at the end of a chunk.  A region of up to 64K following
+      ** the pending byte is never written, so if the pending byte occurs
+      ** near the end of a chunk, that chunk will be too small. */
+#ifndef SQLITE_OMIT_WSD
+      extern int sqlite3PendingByte;
+#else
+      int sqlite3PendingByte = 0x40000000;
+#endif
+      while( (sqlite3PendingByte % pGroup->szChunk)>=(pGroup->szChunk-65536) ){
+        pGroup->szChunk += 65536;
+      }
     }
-    /* bOpen[] vals should all be zero from memset above */
-    pGroup->bOpen = p;
-    p += pGroup->nMaxChunks;
-    pGroup->zName = p;
-    /* save off base filename, name length, and original open flags  */
-    memcpy(pGroup->zName, zName, nName+1);
-    pGroup->nName = nName;
     pGroup->flags = flags;
-    pSubOpen = multiplexSubOpen(pMultiplexOpen, 0, &rc, pOutFlags);
-    if( pSubOpen ){
-      /* if this file is already larger than chunk size, disable 
-      ** the multiplex feature.
-      */
+    rc = multiplexSubFilename(pGroup, 1);
+    if( rc==SQLITE_OK ){
+      pSubOpen = multiplexSubOpen(pGroup, 0, &rc, pOutFlags, 0);
+      if( pSubOpen==0 && rc==SQLITE_OK ) rc = SQLITE_CANTOPEN;
+    }
+    if( rc==SQLITE_OK ){
       sqlite3_int64 sz;
-      int rc2 = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
-      if( (rc2==SQLITE_OK) && (sz>pGroup->nChunkSize) ){
-        pGroup->bEnabled = 0;
+
+      rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
+      if( rc==SQLITE_OK && zName ){
+        int bExists;
+        if( sz==0 ){
+          if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
+            /* If opening a main journal file and the first chunk is zero
+            ** bytes in size, delete any subsequent chunks from the 
+            ** file-system. */
+            int iChunk = 1;
+            do {
+              rc = pOrigVfs->xAccess(pOrigVfs, 
+                  pGroup->aReal[iChunk].z, SQLITE_ACCESS_EXISTS, &bExists
+              );
+              if( rc==SQLITE_OK && bExists ){
+                rc = pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
+                if( rc==SQLITE_OK ){
+                  rc = multiplexSubFilename(pGroup, ++iChunk);
+                }
+              }
+            }while( rc==SQLITE_OK && bExists );
+          }
+        }else{
+          /* If the first overflow file exists and if the size of the main file
+          ** is different from the chunk size, that means the chunk size is set
+          ** set incorrectly.  So fix it.
+          **
+          ** Or, if the first overflow file does not exist and the main file is
+          ** larger than the chunk size, that means the chunk size is too small.
+          ** But we have no way of determining the intended chunk size, so 
+          ** just disable the multiplexor all togethre.
+          */
+          rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[1].z,
+              SQLITE_ACCESS_EXISTS, &bExists);
+          bExists = multiplexSubSize(pGroup, 1, &rc)>0;
+          if( rc==SQLITE_OK && bExists  && sz==(sz&0xffff0000) && sz>0
+              && sz!=pGroup->szChunk ){
+            pGroup->szChunk = (int)sz;
+          }else if( rc==SQLITE_OK && !bExists && sz>pGroup->szChunk ){
+            pGroup->bEnabled = 0;
+          }
+        }
       }
+    }
+
+    if( rc==SQLITE_OK ){
       if( pSubOpen->pMethods->iVersion==1 ){
         pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV1;
       }else{
@@ -369,58 +625,61 @@ static int multiplexOpen(
       if( gMultiplex.pGroups ) gMultiplex.pGroups->pPrev = pGroup;
       gMultiplex.pGroups = pGroup;
     }else{
+      multiplexFreeComponents(pGroup);
       sqlite3_free(pGroup);
     }
   }
   multiplexLeave();
+  sqlite3_free(zToFree);
   return rc;
 }
 
 /*
 ** This is the xDelete method used for the "multiplex" VFS.
-** It attempts to delete the filename specified, as well
-** as additional files with the SQLITE_MULTIPLEX_EXT_FMT extension.
+** It attempts to delete the filename specified.
 */
 static int multiplexDelete(
   sqlite3_vfs *pVfs,         /* The multiplex VFS */
   const char *zName,         /* Name of file to delete */
   int syncDir
 ){
+  int rc;
   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
-  int rc = SQLITE_OK;
-  int nName = multiplexStrlen30(zName);
-  int i;
-
-  UNUSED_PARAMETER(pVfs);
-
-  multiplexEnter();
-  memcpy(gMultiplex.zName, zName, nName+1);
-  for(i=0; i<SQLITE_MULTIPLEX_MAX_CHUNKS; i++){
-    int rc2;
-    int exists = 0;
-    if( i ){
-#ifdef SQLITE_MULTIPLEX_EXT_OVWR
-        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
-            gMultiplex.zName+nName-SQLITE_MULTIPLEX_EXT_SZ, 
-            SQLITE_MULTIPLEX_EXT_FMT, i);
-#else
-        sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
-            gMultiplex.zName+nName, 
-            SQLITE_MULTIPLEX_EXT_FMT, i);
-#endif
-    }
-    rc2 = pOrigVfs->xAccess(pOrigVfs, gMultiplex.zName, 
-        SQLITE_ACCESS_EXISTS, &exists);
-    if( rc2==SQLITE_OK && exists){
-      /* if it exists, delete it */
-      rc2 = pOrigVfs->xDelete(pOrigVfs, gMultiplex.zName, syncDir);
-      if( rc2!=SQLITE_OK ) rc = rc2;
+  rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
+  if( rc==SQLITE_OK ){
+    /* If the main chunk was deleted successfully, also delete any subsequent
+    ** chunks - starting with the last (highest numbered). 
+    */
+    int nName = (int)strlen(zName);
+    char *z;
+    z = sqlite3_malloc(nName + 5);
+    if( z==0 ){
+      rc = SQLITE_IOERR_NOMEM;
     }else{
-      /* stop at first "gap" */
-      break;
+      int iChunk = 0;
+      int bExists;
+      do{
+        multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, ++iChunk, z);
+        rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
+      }while( rc==SQLITE_OK && bExists );
+      while( rc==SQLITE_OK && iChunk>1 ){
+        multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, --iChunk, z);
+        rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
+      }
+      if( rc==SQLITE_OK ){
+        iChunk = 0;
+        do{
+          multiplexFilename(zName, nName, SQLITE_OPEN_WAL, ++iChunk, z);
+          rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
+        }while( rc==SQLITE_OK && bExists );
+        while( rc==SQLITE_OK && iChunk>1 ){
+          multiplexFilename(zName, nName, SQLITE_OPEN_WAL, --iChunk, z);
+          rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
+        }
+      }
     }
+    sqlite3_free(z);
   }
-  multiplexLeave();
   return rc;
 }
 
@@ -469,17 +728,8 @@ static int multiplexClose(sqlite3_file *pConn){
   multiplexConn *p = (multiplexConn*)pConn;
   multiplexGroup *pGroup = p->pGroup;
   int rc = SQLITE_OK;
-  int i;
   multiplexEnter();
-  /* close any open handles */
-  for(i=0; i<pGroup->nMaxChunks; i++){
-    if( pGroup->bOpen[i] ){
-      sqlite3_file *pSubOpen = pGroup->pReal[i];
-      int rc2 = pSubOpen->pMethods->xClose(pSubOpen);
-      if( rc2!=SQLITE_OK ) rc = rc2;
-      pGroup->bOpen[i] = 0;
-    }
-  }
+  multiplexFreeComponents(pGroup);
   /* remove from linked list */
   if( pGroup->pNext ) pGroup->pNext->pPrev = pGroup->pPrev;
   if( pGroup->pPrev ){
@@ -505,19 +755,29 @@ static int multiplexRead(
   multiplexConn *p = (multiplexConn*)pConn;
   multiplexGroup *pGroup = p->pGroup;
   int rc = SQLITE_OK;
-  multiplexEnter();
+  int nMutex = 0;
+  multiplexEnter(); nMutex++;
   if( !pGroup->bEnabled ){
-    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
-    rc = ( !pSubOpen ) ? SQLITE_IOERR_READ : pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    multiplexLeave(); nMutex--;
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_READ;
+    }else{
+      rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
+    }
   }else{
     while( iAmt > 0 ){
-      int i = (int)(iOfst / pGroup->nChunkSize);
-      sqlite3_file *pSubOpen = multiplexSubOpen(p, i, &rc, NULL);
+      int i = (int)(iOfst / pGroup->szChunk);
+      sqlite3_file *pSubOpen;
+      if( nMutex==0 ){ multiplexEnter(); nMutex++; }
+      pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
+      multiplexLeave(); nMutex--;
       if( pSubOpen ){
-        int extra = ((int)(iOfst % pGroup->nChunkSize) + iAmt) - pGroup->nChunkSize;
+        int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) - pGroup->szChunk;
         if( extra<0 ) extra = 0;
         iAmt -= extra;
-        rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst % pGroup->nChunkSize);
+        rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt,
+                                       iOfst % pGroup->szChunk);
         if( rc!=SQLITE_OK ) break;
         pBuf = (char *)pBuf + iAmt;
         iOfst += iAmt;
@@ -528,7 +788,8 @@ static int multiplexRead(
       }
     }
   }
-  multiplexLeave();
+  assert( nMutex==0 || nMutex==1 );
+  if( nMutex ) multiplexLeave();
   return rc;
 }
 
@@ -547,24 +808,26 @@ static int multiplexWrite(
   int rc = SQLITE_OK;
   multiplexEnter();
   if( !pGroup->bEnabled ){
-    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
-    rc = ( !pSubOpen ) ? SQLITE_IOERR_WRITE : pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_WRITE;
+    }else{
+      rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
+    }
   }else{
-    while( iAmt > 0 ){
-      int i = (int)(iOfst / pGroup->nChunkSize);
-      sqlite3_file *pSubOpen = multiplexSubOpen(p, i, &rc, NULL);
+    while( rc==SQLITE_OK && iAmt>0 ){
+      int i = (int)(iOfst / pGroup->szChunk);
+      sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
       if( pSubOpen ){
-        int extra = ((int)(iOfst % pGroup->nChunkSize) + iAmt) - pGroup->nChunkSize;
+        int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) -
+                    pGroup->szChunk;
         if( extra<0 ) extra = 0;
         iAmt -= extra;
-        rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst % pGroup->nChunkSize);
-        if( rc!=SQLITE_OK ) break;
+        rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt,
+                                        iOfst % pGroup->szChunk);
         pBuf = (char *)pBuf + iAmt;
         iOfst += iAmt;
         iAmt = extra;
-      }else{
-        rc = SQLITE_IOERR_WRITE;
-        break;
       }
     }
   }
@@ -582,42 +845,35 @@ static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
   int rc = SQLITE_OK;
   multiplexEnter();
   if( !pGroup->bEnabled ){
-    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
-    rc = ( !pSubOpen ) ? SQLITE_IOERR_TRUNCATE : pSubOpen->pMethods->xTruncate(pSubOpen, size);
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_TRUNCATE;
+    }else{
+      rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
+    }
   }else{
-    int rc2;
     int i;
+    int iBaseGroup = (int)(size / pGroup->szChunk);
     sqlite3_file *pSubOpen;
     sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
-    memcpy(gMultiplex.zName, pGroup->zName, pGroup->nName+1);
     /* delete the chunks above the truncate limit */
-    for(i=(int)(size / pGroup->nChunkSize)+1; i<pGroup->nMaxChunks; i++){
-      /* close any open chunks before deleting them */
-      if( pGroup->bOpen[i] ){
-        pSubOpen = pGroup->pReal[i];
-        rc2 = pSubOpen->pMethods->xClose(pSubOpen);
-        if( rc2!=SQLITE_OK ) rc = SQLITE_IOERR_TRUNCATE;
-        pGroup->bOpen[i] = 0;
+    for(i = pGroup->nReal-1; i>iBaseGroup && rc==SQLITE_OK; i--){
+      if( pGroup->bTruncate ){
+        multiplexSubClose(pGroup, i, pOrigVfs);
+      }else{
+        pSubOpen = multiplexSubOpen(pGroup, i, &rc, 0, 0);
+        if( pSubOpen ){
+          rc = pSubOpen->pMethods->xTruncate(pSubOpen, 0);
+        }
       }
-#ifdef SQLITE_MULTIPLEX_EXT_OVWR
-      sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
-          gMultiplex.zName+pGroup->nName-SQLITE_MULTIPLEX_EXT_SZ, 
-          SQLITE_MULTIPLEX_EXT_FMT, i);
-#else
-      sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
-          gMultiplex.zName+pGroup->nName, 
-          SQLITE_MULTIPLEX_EXT_FMT, i);
-#endif
-      rc2 = pOrigVfs->xDelete(pOrigVfs, gMultiplex.zName, 0);
-      if( rc2!=SQLITE_OK ) rc = SQLITE_IOERR_TRUNCATE;
     }
-    pSubOpen = multiplexSubOpen(p, (int)(size / pGroup->nChunkSize), &rc2, NULL);
-    if( pSubOpen ){
-      rc2 = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->nChunkSize);
-      if( rc2!=SQLITE_OK ) rc = rc2;
-    }else{
-      rc = SQLITE_IOERR_TRUNCATE;
+    if( rc==SQLITE_OK ){
+      pSubOpen = multiplexSubOpen(pGroup, iBaseGroup, &rc, 0, 0);
+      if( pSubOpen ){
+        rc = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->szChunk);
+      }
     }
+    if( rc ) rc = SQLITE_IOERR_TRUNCATE;
   }
   multiplexLeave();
   return rc;
@@ -631,10 +887,9 @@ static int multiplexSync(sqlite3_file *pConn, int flags){
   int rc = SQLITE_OK;
   int i;
   multiplexEnter();
-  for(i=0; i<pGroup->nMaxChunks; i++){
-    /* if we don't have it open, we don't need to sync it */
-    if( pGroup->bOpen[i] ){
-      sqlite3_file *pSubOpen = pGroup->pReal[i];
+  for(i=0; i<pGroup->nReal; i++){
+    sqlite3_file *pSubOpen = pGroup->aReal[i].p;
+    if( pSubOpen ){
       int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
       if( rc2!=SQLITE_OK ) rc = rc2;
     }
@@ -650,58 +905,21 @@ static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
   multiplexConn *p = (multiplexConn*)pConn;
   multiplexGroup *pGroup = p->pGroup;
   int rc = SQLITE_OK;
-  int rc2;
   int i;
   multiplexEnter();
   if( !pGroup->bEnabled ){
-    sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
-    rc = ( !pSubOpen ) ? SQLITE_IOERR_FSTAT : pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
+    sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
+    if( pSubOpen==0 ){
+      rc = SQLITE_IOERR_FSTAT;
+    }else{
+      rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
+    }
   }else{
     *pSize = 0;
-    for(i=0; i<pGroup->nMaxChunks; i++){
-      sqlite3_file *pSubOpen = NULL;
-      /* if not opened already, check to see if the chunk exists */
-      if( pGroup->bOpen[i] ){
-        pSubOpen = pGroup->pReal[i];
-      }else{
-        sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
-        int exists = 0;
-        memcpy(gMultiplex.zName, pGroup->zName, pGroup->nName+1);
-        if( i ){
-#ifdef SQLITE_MULTIPLEX_EXT_OVWR
-          sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
-              gMultiplex.zName+pGroup->nName-SQLITE_MULTIPLEX_EXT_SZ, 
-              SQLITE_MULTIPLEX_EXT_FMT, i);
-#else
-          sqlite3_snprintf(SQLITE_MULTIPLEX_EXT_SZ+1, 
-              gMultiplex.zName+pGroup->nName, 
-              SQLITE_MULTIPLEX_EXT_FMT, i);
-#endif
-        }
-        rc2 = pOrigVfs->xAccess(pOrigVfs, gMultiplex.zName, 
-            SQLITE_ACCESS_EXISTS, &exists);
-        if( rc2==SQLITE_OK && exists){
-          /* if it exists, open it */
-          pSubOpen = multiplexSubOpen(p, i, &rc, NULL);
-        }else{
-          /* stop at first "gap" */
-          break;
-        }
-      }
-      if( pSubOpen ){
-        sqlite3_int64 sz;
-        rc2 = pSubOpen->pMethods->xFileSize(pSubOpen, &sz);
-        if( rc2!=SQLITE_OK ){
-          rc = rc2;
-        }else{
-          if( sz>pGroup->nChunkSize ){
-            rc = SQLITE_IOERR_FSTAT;
-          }
-          *pSize += sz;
-        }
-      }else{
-        break;
-      }
+    for(i=0; rc==SQLITE_OK; i++){
+      sqlite3_int64 sz = multiplexSubSize(pGroup, i, &rc);
+      if( sz==0 ) break;
+      *pSize = i*(sqlite3_int64)pGroup->szChunk + sz;
     }
   }
   multiplexLeave();
@@ -713,7 +931,7 @@ static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
 static int multiplexLock(sqlite3_file *pConn, int lock){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     return pSubOpen->pMethods->xLock(pSubOpen, lock);
   }
@@ -725,7 +943,7 @@ static int multiplexLock(sqlite3_file *pConn, int lock){
 static int multiplexUnlock(sqlite3_file *pConn, int lock){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
   }
@@ -737,7 +955,7 @@ static int multiplexUnlock(sqlite3_file *pConn, int lock){
 static int multiplexCheckReservedLock(sqlite3_file *pConn, int *pResOut){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
   }
@@ -764,38 +982,53 @@ static int multiplexFileControl(sqlite3_file *pConn, int op, void *pArg){
       break;
     case MULTIPLEX_CTRL_SET_CHUNK_SIZE:
       if( pArg ) {
-        int nChunkSize = *(int *)pArg;
-        if( nChunkSize<1 ){
+        unsigned int szChunk = *(unsigned*)pArg;
+        if( szChunk<1 ){
           rc = SQLITE_MISUSE;
         }else{
           /* Round up to nearest multiple of MAX_PAGE_SIZE. */
-          nChunkSize = (nChunkSize + (MAX_PAGE_SIZE-1));
-          nChunkSize &= ~(MAX_PAGE_SIZE-1);
-          pGroup->nChunkSize = nChunkSize;
+          szChunk = (szChunk + (MAX_PAGE_SIZE-1));
+          szChunk &= ~(MAX_PAGE_SIZE-1);
+          pGroup->szChunk = szChunk;
           rc = SQLITE_OK;
         }
       }
       break;
     case MULTIPLEX_CTRL_SET_MAX_CHUNKS:
-      if( pArg ) {
-        int nMaxChunks = *(int *)pArg;
-        if(( nMaxChunks<1 ) || ( nMaxChunks>SQLITE_MULTIPLEX_MAX_CHUNKS )){
-          rc = SQLITE_MISUSE;
-        }else{
-          pGroup->nMaxChunks = nMaxChunks;
-          rc = SQLITE_OK;
-        }
-      }
+      rc = SQLITE_OK;
       break;
     case SQLITE_FCNTL_SIZE_HINT:
     case SQLITE_FCNTL_CHUNK_SIZE:
       /* no-op these */
       rc = SQLITE_OK;
       break;
+    case SQLITE_FCNTL_PRAGMA: {
+      char **aFcntl = (char**)pArg;
+      if( aFcntl[1] && sqlite3_stricmp(aFcntl[1],"multiplex_truncate")==0 ){
+        if( aFcntl[2] && aFcntl[2][0] ){
+          if( sqlite3_stricmp(aFcntl[2], "on")==0
+           || sqlite3_stricmp(aFcntl[2], "1")==0 ){
+            pGroup->bTruncate = 1;
+          }else
+          if( sqlite3_stricmp(aFcntl[2], "off")==0
+           || sqlite3_stricmp(aFcntl[2], "0")==0 ){
+            pGroup->bTruncate = 0;
+          }
+        }
+        aFcntl[0] = sqlite3_mprintf(pGroup->bTruncate ? "on" : "off");
+        rc = SQLITE_OK;
+        break;
+      }
+      /* If the multiplexor does not handle the pragma, pass it through
+      ** into the default case. */
+    }
     default:
-      pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+      pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
       if( pSubOpen ){
         rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
+        if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
+         *(char**)pArg = sqlite3_mprintf("multiplex/%z", *(char**)pArg);
+        }
       }
       break;
   }
@@ -807,8 +1040,8 @@ static int multiplexFileControl(sqlite3_file *pConn, int op, void *pArg){
 static int multiplexSectorSize(sqlite3_file *pConn){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
-  if( pSubOpen ){
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
+  if( pSubOpen && pSubOpen->pMethods->xSectorSize ){
     return pSubOpen->pMethods->xSectorSize(pSubOpen);
   }
   return DEFAULT_SECTOR_SIZE;
@@ -819,7 +1052,7 @@ static int multiplexSectorSize(sqlite3_file *pConn){
 static int multiplexDeviceCharacteristics(sqlite3_file *pConn){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
   }
@@ -837,9 +1070,9 @@ static int multiplexShmMap(
 ){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
-    return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend, pp);
+    return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend,pp);
   }
   return SQLITE_IOERR;
 }
@@ -854,7 +1087,7 @@ static int multiplexShmLock(
 ){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
   }
@@ -866,7 +1099,7 @@ static int multiplexShmLock(
 static void multiplexShmBarrier(sqlite3_file *pConn){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     pSubOpen->pMethods->xShmBarrier(pSubOpen);
   }
@@ -877,7 +1110,7 @@ static void multiplexShmBarrier(sqlite3_file *pConn){
 static int multiplexShmUnmap(sqlite3_file *pConn, int deleteFlag){
   multiplexConn *p = (multiplexConn*)pConn;
   int rc;
-  sqlite3_file *pSubOpen = multiplexSubOpen(p, 0, &rc, NULL);
+  sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
   if( pSubOpen ){
     return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
   }
@@ -907,11 +1140,6 @@ int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
   if( !gMultiplex.pMutex ){
     return SQLITE_NOMEM;
   }
-  gMultiplex.zName = sqlite3_malloc(pOrigVfs->mxPathname);
-  if( !gMultiplex.zName ){
-    sqlite3_mutex_free(gMultiplex.pMutex);
-    return SQLITE_NOMEM;
-  }
   gMultiplex.pGroups = NULL;
   gMultiplex.isInitialized = 1;
   gMultiplex.pOrigVfs = pOrigVfs;
@@ -944,7 +1172,8 @@ int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
   gMultiplex.sIoMethodsV1.xCheckReservedLock = multiplexCheckReservedLock;
   gMultiplex.sIoMethodsV1.xFileControl = multiplexFileControl;
   gMultiplex.sIoMethodsV1.xSectorSize = multiplexSectorSize;
-  gMultiplex.sIoMethodsV1.xDeviceCharacteristics = multiplexDeviceCharacteristics;
+  gMultiplex.sIoMethodsV1.xDeviceCharacteristics =
+                                            multiplexDeviceCharacteristics;
   gMultiplex.sIoMethodsV2 = gMultiplex.sIoMethodsV1;
   gMultiplex.sIoMethodsV2.iVersion = 2;
   gMultiplex.sIoMethodsV2.xShmMap = multiplexShmMap;
@@ -967,21 +1196,26 @@ int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
 ** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
 ** shutting down in order to free all remaining multiplex groups.
 */
-int sqlite3_multiplex_shutdown(void){
+int sqlite3_multiplex_shutdown(int eForce){
+  int rc = SQLITE_OK;
   if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
-  if( gMultiplex.pGroups ) return SQLITE_MISUSE;
+  if( gMultiplex.pGroups ){
+    sqlite3_log(SQLITE_MISUSE, "sqlite3_multiplex_shutdown() called "
+                "while database connections are still open");
+    if( !eForce ) return SQLITE_MISUSE;
+    rc = SQLITE_MISUSE;
+  }
   gMultiplex.isInitialized = 0;
-  sqlite3_free(gMultiplex.zName);
   sqlite3_mutex_free(gMultiplex.pMutex);
   sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
   memset(&gMultiplex, 0, sizeof(gMultiplex));
-  return SQLITE_OK;
+  return rc;
 }
 
 /***************************** Test Code ***********************************/
 #ifdef SQLITE_TEST
 #include <tcl.h>
-extern const char *sqlite3TestErrorName(int);
+extern const char *sqlite3ErrName(int);
 
 
 /*
@@ -1010,7 +1244,7 @@ static int test_multiplex_initialize(
 
   /* Call sqlite3_multiplex_initialize() */
   rc = sqlite3_multiplex_initialize(zName, makeDefault);
-  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
 
   return TCL_OK;
 }
@@ -1028,14 +1262,17 @@ static int test_multiplex_shutdown(
 
   UNUSED_PARAMETER(clientData);
 
-  if( objc!=1 ){
-    Tcl_WrongNumArgs(interp, 1, objv, "");
+  if( objc==2 && strcmp(Tcl_GetString(objv[1]),"-force")!=0 ){
+    objc = 3;
+  }
+  if( (objc!=1 && objc!=2) ){
+    Tcl_WrongNumArgs(interp, 1, objv, "?-force?");
     return TCL_ERROR;
   }
 
   /* Call sqlite3_multiplex_shutdown() */
-  rc = sqlite3_multiplex_shutdown();
-  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+  rc = sqlite3_multiplex_shutdown(objc==2);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
 
   return TCL_OK;
 }
@@ -1064,25 +1301,29 @@ static int test_multiplex_dump(
   for(pGroup=gMultiplex.pGroups; pGroup; pGroup=pGroup->pNext){
     pGroupTerm = Tcl_NewObj();
 
-    pGroup->zName[pGroup->nName] = '\0';
-    Tcl_ListObjAppendElement(interp, pGroupTerm,
+    if( pGroup->zName ){
+      pGroup->zName[pGroup->nName] = '\0';
+      Tcl_ListObjAppendElement(interp, pGroupTerm,
           Tcl_NewStringObj(pGroup->zName, -1));
+    }else{
+      Tcl_ListObjAppendElement(interp, pGroupTerm, Tcl_NewObj());
+    }
     Tcl_ListObjAppendElement(interp, pGroupTerm,
           Tcl_NewIntObj(pGroup->nName));
     Tcl_ListObjAppendElement(interp, pGroupTerm,
           Tcl_NewIntObj(pGroup->flags));
 
     /* count number of chunks with open handles */
-    for(i=0; i<pGroup->nMaxChunks; i++){
-      if( pGroup->bOpen[i] ) nChunks++;
+    for(i=0; i<pGroup->nReal; i++){
+      if( pGroup->aReal[i].p!=0 ) nChunks++;
     }
     Tcl_ListObjAppendElement(interp, pGroupTerm,
           Tcl_NewIntObj(nChunks));
 
     Tcl_ListObjAppendElement(interp, pGroupTerm,
-          Tcl_NewIntObj(pGroup->nChunkSize));
+          Tcl_NewIntObj(pGroup->szChunk));
     Tcl_ListObjAppendElement(interp, pGroupTerm,
-          Tcl_NewIntObj(pGroup->nMaxChunks));
+          Tcl_NewIntObj(pGroup->nReal));
 
     Tcl_ListObjAppendElement(interp, pResult, pGroupTerm);
   }
@@ -1149,7 +1390,7 @@ static int test_multiplex_control(
   }
 
   rc = sqlite3_file_control(db, Tcl_GetString(objv[2]), aSub[idx].op, pArg);
-  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+  Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
   return (rc==SQLITE_OK) ? TCL_OK : TCL_ERROR;
 }