Index: ext/session/session1.test
==================================================================
--- ext/session/session1.test
+++ ext/session/session1.test
@@ -652,10 +652,17 @@
   execsql BEGIN
   catch { sqlite3changeset_apply_v2 -nosavepoint db $C xConflict } msg
   execsql { SELECT * FROM x1 }
 } {1 one 2 two 3 iii}
 execsql ROLLBACK
+
+do_test $tn.14.1 { sqlite3session_config strm_size -1 } 64
+do_test $tn.14.2 { sqlite3session_config strm_size 65536 } 65536
+do_test $tn.14.3 { sqlite3session_config strm_size 64 } 64
+do_test $tn.14.4 { 
+  list [catch {sqlite3session_config invalid 123} msg] $msg
+} {1 SQLITE_MISUSE}
 
 }]
 }
 
 

Index: ext/session/sqlite3session.c
==================================================================
--- ext/session/sqlite3session.c
+++ ext/session/sqlite3session.c
@@ -23,10 +23,12 @@
 # else
 #   define SESSIONS_STRM_CHUNK_SIZE 1024
 # endif
 #endif
 
+static int sessions_strm_chunk_size = SESSIONS_STRM_CHUNK_SIZE;
+
 typedef struct SessionHook SessionHook;
 struct SessionHook {
   void *pCtx;
   int (*xOld)(void*,int,sqlite3_value**);
   int (*xNew)(void*,int,sqlite3_value**);
@@ -2395,16 +2397,16 @@
           }
           if( rc==SQLITE_OK ){
             rc = sqlite3_reset(pSel);
           }
 
-          /* If the buffer is now larger than SESSIONS_STRM_CHUNK_SIZE, pass
+          /* If the buffer is now larger than sessions_strm_chunk_size, pass
           ** its contents to the xOutput() callback. */
           if( xOutput 
            && rc==SQLITE_OK 
            && buf.nBuf>nNoop 
-           && buf.nBuf>SESSIONS_STRM_CHUNK_SIZE 
+           && buf.nBuf>sessions_strm_chunk_size 
           ){
             rc = xOutput(pOut, (void*)buf.aBuf, buf.nBuf);
             nNoop = -1;
             buf.nBuf = 0;
           }
@@ -2612,11 +2614,11 @@
 /*
 ** If the SessionInput object passed as the only argument is a streaming
 ** object and the buffer is full, discard some data to free up space.
 */
 static void sessionDiscardData(SessionInput *pIn){
-  if( pIn->xInput && pIn->iNext>=SESSIONS_STRM_CHUNK_SIZE ){
+  if( pIn->xInput && pIn->iNext>=sessions_strm_chunk_size ){
     int nMove = pIn->buf.nBuf - pIn->iNext;
     assert( nMove>=0 );
     if( nMove>0 ){
       memmove(pIn->buf.aBuf, &pIn->buf.aBuf[pIn->iNext], nMove);
     }
@@ -2635,11 +2637,11 @@
 */
 static int sessionInputBuffer(SessionInput *pIn, int nByte){
   int rc = SQLITE_OK;
   if( pIn->xInput ){
     while( !pIn->bEof && (pIn->iNext+nByte)>=pIn->nData && rc==SQLITE_OK ){
-      int nNew = SESSIONS_STRM_CHUNK_SIZE;
+      int nNew = sessions_strm_chunk_size;
 
       if( pIn->bNoDiscard==0 ) sessionDiscardData(pIn);
       if( SQLITE_OK==sessionBufferGrow(&pIn->buf, nNew, &rc) ){
         rc = pIn->xInput(pIn->pIn, &pIn->buf.aBuf[pIn->buf.nBuf], &nNew);
         if( nNew==0 ){
@@ -3360,11 +3362,11 @@
         rc = SQLITE_CORRUPT_BKPT;
         goto finished_invert;
     }
 
     assert( rc==SQLITE_OK );
-    if( xOutput && sOut.nBuf>=SESSIONS_STRM_CHUNK_SIZE ){
+    if( xOutput && sOut.nBuf>=sessions_strm_chunk_size ){
       rc = xOutput(pOut, sOut.aBuf, sOut.nBuf);
       sOut.nBuf = 0;
       if( rc!=SQLITE_OK ) goto finished_invert;
     }
   }
@@ -4893,11 +4895,11 @@
       SessionChange *p;
       for(p=pTab->apChange[i]; p; p=p->pNext){
         sessionAppendByte(&buf, p->op, &rc);
         sessionAppendByte(&buf, p->bIndirect, &rc);
         sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
-        if( rc==SQLITE_OK && xOutput && buf.nBuf>=SESSIONS_STRM_CHUNK_SIZE ){
+        if( rc==SQLITE_OK && xOutput && buf.nBuf>=sessions_strm_chunk_size ){
           rc = xOutput(pOut, buf.aBuf, buf.nBuf);
           buf.nBuf = 0;
         }
       }
     }
@@ -5289,11 +5291,11 @@
     if( bDone==0 ){
       sessionAppendByte(&sOut, pIter->op, &rc);
       sessionAppendByte(&sOut, pIter->bIndirect, &rc);
       sessionAppendBlob(&sOut, aRec, nRec, &rc);
     }
-    if( rc==SQLITE_OK && xOutput && sOut.nBuf>SESSIONS_STRM_CHUNK_SIZE ){
+    if( rc==SQLITE_OK && xOutput && sOut.nBuf>sessions_strm_chunk_size ){
       rc = xOutput(pOut, sOut.aBuf, sOut.nBuf);
       sOut.nBuf = 0;
     }
     if( rc ) break;
   }
@@ -5399,7 +5401,28 @@
   if( p ){
     sessionDeleteTable(p->grp.pList);
     sqlite3_free(p);
   }
 }
+
+/* 
+** Global configuration
+*/
+int sqlite3session_config(int op, void *pArg){
+  int rc = SQLITE_OK;
+  switch( op ){
+    case SQLITE_SESSION_CONFIG_STRMSIZE: {
+      int *pInt = (int*)pArg;
+      if( *pInt>0 ){
+        sessions_strm_chunk_size = *pInt;
+      }
+      *pInt = sessions_strm_chunk_size;
+      break;
+    }
+    default:
+      rc = SQLITE_MISUSE;
+      break;
+  }
+  return rc;
+}
 
 #endif /* SQLITE_ENABLE_SESSION && SQLITE_ENABLE_PREUPDATE_HOOK */

Index: ext/session/sqlite3session.h
==================================================================
--- ext/session/sqlite3session.h
+++ ext/session/sqlite3session.h
@@ -1608,10 +1608,49 @@
   void *pIn,
   int (*xOutput)(void *pOut, const void *pData, int nData),
   void *pOut
 );
 
+/*
+** CAPI3REF: Configure global parameters
+**
+** The sqlite3session_config() interface is used to make global configuration
+** changes to the sessions module in order to tune it to the specific needs 
+** of the application.
+**
+** The sqlite3session_config() interface is not threadsafe. If it is invoked
+** while any other thread is inside any other sessions method then the
+** results are undefined. Furthermore, if it is invoked after any sessions
+** related objects have been created, the results are also undefined. 
+**
+** The first argument to the sqlite3session_config() function must be one
+** of the SQLITE_SESSION_CONFIG_XXX constants defined below. The 
+** interpretation of the (void*) value passed as the second parameter and
+** the effect of calling this function depends on the value of the first
+** parameter.
+**
+** <dl>
+** <dt>SQLITE_SESSION_CONFIG_STRMSIZE<dd>
+**    By default, the sessions module streaming interfaces attempt to input
+**    and output data in approximately 1 KiB chunks. This operand may be used
+**    to set and query the value of this configuration setting. The pointer
+**    passed as the second argument must point to a value of type (int).
+**    If this value is greater than 0, it is used as the new streaming data
+**    chunk size for both input and output. Before returning, the (int) value
+**    pointed to by pArg is set to the final value of the streaming interface
+**    chunk size.
+** </dl>
+**
+** This function returns SQLITE_OK if successful, or an SQLite error code
+** otherwise.
+*/
+int sqlite3session_config(int op, void *pArg);
+
+/*
+** CAPI3REF: Values for sqlite3session_config().
+*/
+#define SQLITE_SESSION_CONFIG_STRMSIZE 1
 
 /*
 ** Make sure we can call this stuff from C++.
 */
 #ifdef __cplusplus

Index: ext/session/test_session.c
==================================================================
--- ext/session/test_session.c
+++ ext/session/test_session.c
@@ -1236,10 +1236,49 @@
       (ClientData)pNew, test_rebaser_del
   );
   Tcl_SetObjResult(interp, objv[1]);
   return TCL_OK;
 }
+
+/*
+** tclcmd: sqlite3rebaser_configure OP VALUE
+*/
+static int SQLITE_TCLAPI test_sqlite3session_config(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct ConfigOpt {
+    const char *zSub;
+    int op;
+  } aSub[] = {
+    { "strm_size",    SQLITE_SESSION_CONFIG_STRMSIZE },
+    { "invalid",      0 },
+    { 0 }
+  };
+  int rc;
+  int iSub;
+  int iVal;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "OP VALUE");
+    return SQLITE_ERROR;
+  }
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[1], aSub, sizeof(aSub[0]), "sub-command", 0, &iSub
+  );
+  if( rc!=TCL_OK ) return rc;
+  if( Tcl_GetIntFromObj(interp, objv[2], &iVal) ) return TCL_ERROR;
+
+  rc = sqlite3session_config(aSub[iSub].op, (void*)&iVal);
+  if( rc!=SQLITE_OK ){
+    return test_session_error(interp, rc, 0);
+  }
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(iVal));
+  return TCL_OK;
+}
 
 int TestSession_Init(Tcl_Interp *interp){
   struct Cmd {
     const char *zCmd;
     Tcl_ObjCmdProc *xProc;
@@ -1252,10 +1291,11 @@
     { "sqlite3changeset_apply_v2", test_sqlite3changeset_apply_v2 },
     { "sqlite3changeset_apply_replace_all", 
       test_sqlite3changeset_apply_replace_all },
     { "sql_exec_changeset", test_sql_exec_changeset },
     { "sqlite3rebaser_create", test_sqlite3rebaser_create },
+    { "sqlite3session_config", test_sqlite3session_config },
   };
   int i;
 
   for(i=0; i<sizeof(aCmd)/sizeof(struct Cmd); i++){
     struct Cmd *p = &aCmd[i];