From: dan <Dan Kennedy>
Date: Wed, 21 Apr 2021 20:52:17 +0000 (+0000)
Subject: Add the experimental sqlite3session_changeset_size() API.
X-Git-Tag: version-3.36.0~164^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a23a873fbb02bdb20923aae7d2476f07d4245bc3;p=thirdparty%2Fsqlite.git

Add the experimental sqlite3session_changeset_size() API.

FossilOrigin-Name: b5564a6fd54875db1de884fdc0e5eeabcd6aa5595ad03a8a60843503e830a2d8
---

diff --git a/ext/session/sessionsize.test b/ext/session/sessionsize.test
new file mode 100644
index 0000000000..8347097e96
--- /dev/null
+++ b/ext/session/sessionsize.test
@@ -0,0 +1,108 @@
+# 2021 April 22
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.
+#
+
+if {![info exists testdir]} {
+  set testdir [file join [file dirname [info script]] .. .. test]
+} 
+source [file join [file dirname [info script]] session_common.tcl]
+source $testdir/tester.tcl
+ifcapable !session {finish_test; return}
+
+set testprefix sessionsize
+
+proc do_changeset_size_test {tn sql} {
+  sqlite3session S db main
+  S attach *
+  db eval $sql
+
+  set sz [S changeset_size]
+  set C [S changeset]
+  set szC [string length $C]
+  S delete
+
+  do_test $tn "expr $sz" $szC
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
+  INSERT INTO t1 VALUES(1, 'abc', 'def');
+  INSERT INTO t1 VALUES(2, 'ghi', 'jkl');
+}
+
+do_changeset_size_test 1.1 {
+  INSERT INTO t1 VALUES(3, 'hello', 'world');
+}
+
+do_changeset_size_test 1.2 {
+  DELETE FROM t1 WHERE a=2;
+}
+
+do_changeset_size_test 1.3 {
+  DELETE FROM t1 WHERE a=3;
+  INSERT INTO t1 VALUES(3, 1, 2);
+}
+
+do_changeset_size_test 1.4 {
+  UPDATE t1 SET c='hello world' WHERE a=3;
+}
+
+#-------------------------------------------------------------------------
+
+do_execsql_test 2.0 {
+  CREATE TABlE t2(a, b, c, d, PRIMARY KEY(a, b)) WITHOUT ROWID;
+  CREATE TABlE t3(a, b, c, d PRIMARY KEY);
+}
+
+do_changeset_size_test 2.1 {
+  WITH s(i) AS (
+    SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<50
+  )
+  INSERT INTO t2 SELECT i, i+1, i+2, i+3 FROM s;
+
+  UPDATE t2 SET c=randomblob(a) WHERE a>10
+}
+
+do_changeset_size_test 2.2 {
+  DELETE FROM t2 WHERE a=1;
+  INSERT INTO t2 VALUES(1, 4, 3, 4);
+}
+
+do_changeset_size_test 2.2 {
+  UPDATE t2 SET b=4 WHERE a=2
+}
+
+do_changeset_size_test 2.3 {
+  INSERT INTO t2 VALUES('a', 'b', 'c', 'd');
+  UPDATE t2 SET c='qwertyuiop' WHERE a='a';
+}
+
+do_changeset_size_test 2.4 {
+  DELETE FROM t2 WHERE a='a';
+  INSERT INTO t2 VALUES('a', 'b', 'c', 'd');
+}
+
+do_changeset_size_test 2.5 {
+  UPDATE t2 SET a='aa', b='bb' WHERE (a, b) = ('a', 'b');
+}
+
+do_changeset_size_test 2.6 {
+  UPDATE t2 SET a='a', b='b' WHERE (a, b) = ('aa', 'bb');
+}
+
+do_changeset_size_test 2.7 {
+  INSERT INTO t3 DEFAULT VALUES;
+  INSERT INTO t3 VALUES(1,2,3,4);
+}
+
+finish_test
+
diff --git a/ext/session/sqlite3session.c b/ext/session/sqlite3session.c
index 8210056a89..077a6e0900 100644
--- a/ext/session/sqlite3session.c
+++ b/ext/session/sqlite3session.c
@@ -49,6 +49,7 @@ struct sqlite3_session {
   void *pFilterCtx;               /* First argument to pass to xTableFilter */
   int (*xTableFilter)(void *pCtx, const char *zTab);
   i64 nMalloc;                    /* Number of bytes of data allocated */
+  i64 nMaxChangesetSize;
   sqlite3_value *pZeroBlob;       /* Value containing X'' */
   sqlite3_session *pNext;         /* Next session object on same db. */
   SessionTable *pTable;           /* List of attached tables */
@@ -291,8 +292,9 @@ struct SessionTable {
 ** this structure stored in a SessionTable.aChange[] hash table.
 */
 struct SessionChange {
-  int op;                         /* One of UPDATE, DELETE, INSERT */
-  int bIndirect;                  /* True if this change is "indirect" */
+  u8 op;                          /* One of UPDATE, DELETE, INSERT */
+  u8 bIndirect;                   /* True if this change is "indirect" */
+  int nMaxSize;                   /* Max size of eventual changeset record */
   int nRecord;                    /* Number of bytes in buffer aRecord[] */
   u8 *aRecord;                    /* Buffer containing old.* record */
   SessionChange *pNext;           /* For hash-table collisions */
@@ -1121,6 +1123,10 @@ static int sessionInitTable(sqlite3_session *pSession, SessionTable *pTab){
       if( 0==sqlite3_stricmp("sqlite_stat1", pTab->zName) ){
         pTab->bStat1 = 1;
       }
+
+      pSession->nMaxChangesetSize += (
+        1 + sessionVarintLen(pTab->nCol) + pTab->nCol + strlen(pTab->zName) + 1
+      );
     }
   }
   return (pSession->rc || pTab->abPK==0);
@@ -1166,6 +1172,103 @@ static int sessionStat1Depth(void *pCtx){
   return p->hook.xDepth(p->hook.pCtx);
 }
 
+static int sessionUpdateMaxSize(
+  int op,
+  sqlite3_session *pSession,      /* Session object pTab is attached to */
+  SessionTable *pTab,             /* Table that change applies to */
+  SessionChange *pC               /* Update pC->nMaxSize */
+){
+  i64 nNew = 2;
+  if( pC->op==SQLITE_INSERT ){
+    if( op!=SQLITE_DELETE ){
+      int ii;
+      for(ii=0; ii<pTab->nCol; ii++){
+        sqlite3_value *p = 0;
+        pSession->hook.xNew(pSession->hook.pCtx, ii, &p);
+        sessionSerializeValue(0, p, &nNew);
+      }
+    }
+  }else if( op==SQLITE_DELETE ){
+    nNew += pC->nRecord;
+    if( sqlite3_preupdate_blobwrite(pSession->db)>=0 ){
+      nNew += pC->nRecord;
+    }
+  }else{
+    int ii;
+    u8 *pCsr = pC->aRecord;
+    for(ii=0; ii<pTab->nCol; ii++){
+      int bChanged = 1;
+      int nOld = 0;
+      int eType;
+      sqlite3_value *p = 0;
+      pSession->hook.xNew(pSession->hook.pCtx, ii, &p);
+      if( p==0 ){
+        return SQLITE_NOMEM;
+      }
+
+      eType = *pCsr++;
+      switch( eType ){
+        case SQLITE_NULL:
+          bChanged = sqlite3_value_type(p)!=SQLITE_NULL;
+          break;
+
+        case SQLITE_FLOAT:
+        case SQLITE_INTEGER: {
+          if( eType==sqlite3_value_type(p) ){
+            sqlite3_int64 iVal = sessionGetI64(pCsr);
+            if( eType==SQLITE_INTEGER ){
+              bChanged = (iVal!=sqlite3_value_int64(p));
+            }else{
+              double dVal;
+              memcpy(&dVal, &iVal, 8);
+              bChanged = (dVal!=sqlite3_value_double(p));
+            }
+          }
+          nOld = 8;
+          pCsr += 8;
+          break;
+        }
+
+        default: {
+          int nByte;
+          nOld = sessionVarintGet(pCsr, &nByte);
+          pCsr += nOld;
+          nOld += nByte;
+          assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
+          if( eType==sqlite3_value_type(p) 
+           && nByte==sqlite3_value_bytes(p)
+           && (nByte==0 || 0==memcmp(pCsr, sqlite3_value_blob(p), nByte))
+          ){
+            bChanged = 0;
+          }
+          pCsr += nByte;
+          break;
+        }
+      }
+
+      if( bChanged && pTab->abPK[ii] ){
+        nNew = pC->nRecord + 2;
+        break;
+      }
+
+      if( bChanged ){
+        nNew += 1 + nOld;
+        sessionSerializeValue(0, p, &nNew);
+      }else if( pTab->abPK[ii] ){
+        nNew += 2 + nOld;
+      }else{
+        nNew += 2;
+      }
+    }
+  }
+
+  if( nNew>pC->nMaxSize ){
+    int nIncr = nNew - pC->nMaxSize;
+    pC->nMaxSize = nNew;
+    pSession->nMaxChangesetSize += nIncr;
+  }
+  return SQLITE_OK;
+}
 
 /*
 ** This function is only called from with a pre-update-hook reporting a 
@@ -1239,7 +1342,6 @@ static void sessionPreupdateOneChange(
       /* Create a new change object containing all the old values (if
       ** this is an SQLITE_UPDATE or SQLITE_DELETE), or just the PK
       ** values (if this is an INSERT). */
-      SessionChange *pChange; /* New change object */
       sqlite3_int64 nByte;    /* Number of bytes to allocate */
       int i;                  /* Used to iterate through columns */
   
@@ -1265,13 +1367,13 @@ static void sessionPreupdateOneChange(
       }
   
       /* Allocate the change object */
-      pChange = (SessionChange *)sessionMalloc64(pSession, nByte);
-      if( !pChange ){
+      pC = (SessionChange *)sessionMalloc64(pSession, nByte);
+      if( !pC ){
         rc = SQLITE_NOMEM;
         goto error_out;
       }else{
-        memset(pChange, 0, sizeof(SessionChange));
-        pChange->aRecord = (u8 *)&pChange[1];
+        memset(pC, 0, sizeof(SessionChange));
+        pC->aRecord = (u8 *)&pC[1];
       }
   
       /* Populate the change object. None of the preupdate_old(),
@@ -1286,17 +1388,17 @@ static void sessionPreupdateOneChange(
         }else if( pTab->abPK[i] ){
           pSession->hook.xNew(pSession->hook.pCtx, i, &p);
         }
-        sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);
+        sessionSerializeValue(&pC->aRecord[nByte], p, &nByte);
       }
 
       /* Add the change to the hash-table */
       if( pSession->bIndirect || pSession->hook.xDepth(pSession->hook.pCtx) ){
-        pChange->bIndirect = 1;
+        pC->bIndirect = 1;
       }
-      pChange->nRecord = nByte;
-      pChange->op = op;
-      pChange->pNext = pTab->apChange[iHash];
-      pTab->apChange[iHash] = pChange;
+      pC->nRecord = nByte;
+      pC->op = op;
+      pC->pNext = pTab->apChange[iHash];
+      pTab->apChange[iHash] = pC;
 
     }else if( pC->bIndirect ){
       /* If the existing change is considered "indirect", but this current
@@ -1307,8 +1409,12 @@ static void sessionPreupdateOneChange(
         pC->bIndirect = 0;
       }
     }
+
+    assert( rc==SQLITE_OK );
+    rc = sessionUpdateMaxSize(op, pSession, pTab, pC);
   }
 
+
   /* If an error has occurred, mark the session object as failed. */
  error_out:
   if( pTab->bStat1 ){
@@ -2520,7 +2626,9 @@ int sqlite3session_changeset(
   int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
   void **ppChangeset              /* OUT: Buffer containing changeset */
 ){
-  return sessionGenerateChangeset(pSession, 0, 0, 0, pnChangeset, ppChangeset);
+  int rc = sessionGenerateChangeset(pSession, 0, 0, 0, pnChangeset,ppChangeset);
+  assert( rc || pnChangeset==0 || *pnChangeset<=pSession->nMaxChangesetSize );
+  return rc;
 }
 
 /*
@@ -2612,6 +2720,13 @@ sqlite3_int64 sqlite3session_memory_used(sqlite3_session *pSession){
   return pSession->nMalloc;
 }
 
+/*
+** Return the maximum size of sqlite3session_changeset() output.
+*/
+sqlite3_int64 sqlite3session_changeset_size(sqlite3_session *pSession){
+  return pSession->nMaxChangesetSize;
+}
+
 /*
 ** Do the work for either sqlite3changeset_start() or start_strm().
 */
diff --git a/ext/session/sqlite3session.h b/ext/session/sqlite3session.h
index 9ebf360ea3..78d25ba0f3 100644
--- a/ext/session/sqlite3session.h
+++ b/ext/session/sqlite3session.h
@@ -323,6 +323,17 @@ int sqlite3session_changeset(
   void **ppChangeset              /* OUT: Buffer containing changeset */
 );
 
+/*
+** CAPI3REF: Load The Difference Between Tables Into A Session
+** METHOD: sqlite3session_changeset_size()
+**
+** This function returns an upper limit, in bytes, of the size of the
+** changeset that might be produced if sqlite3session_changeset() were
+** called. The final changeset size might be equal to or smaller than
+** the size in bytes returned by this function.
+*/
+sqlite3_int64 sqlite3session_changeset_size(sqlite3_session *pSession);
+
 /*
 ** CAPI3REF: Load The Difference Between Tables Into A Session
 ** METHOD: sqlite3_session
diff --git a/ext/session/test_session.c b/ext/session/test_session.c
index c3898fd860..b7c96b2657 100644
--- a/ext/session/test_session.c
+++ b/ext/session/test_session.c
@@ -246,6 +246,7 @@ static int SQLITE_TCLAPI test_session_cmd(
     { "patchset",     0, "",           }, /* 7 */
     { "diff",         2, "FROMDB TBL", }, /* 8 */
     { "memory_used",  0, "",           }, /* 9 */
+    { "changeset_size", 0, "",         }, /* 10 */
     { 0 }
   };
   int iSub;
@@ -357,6 +358,12 @@ static int SQLITE_TCLAPI test_session_cmd(
       Tcl_SetObjResult(interp, Tcl_NewWideIntObj(nMalloc));
       break;
     }
+
+    case 10: {
+      sqlite3_int64 nSize = sqlite3session_changeset_size(pSession);
+      Tcl_SetObjResult(interp, Tcl_NewWideIntObj(nSize));
+      break;
+    }
   }
 
   return TCL_OK;
diff --git a/manifest b/manifest
index 8307184414..0c5737175f 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\srecent\sdbsqlfuzz\stest\scases\sto\stest/fuzzdata8.db.
-D 2021-04-21T12:03:36.478
+C Add\sthe\sexperimental\ssqlite3session_changeset_size()\sAPI.
+D 2021-04-21T20:52:17.903
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -453,11 +453,12 @@ F ext/session/sessioninvert.test 04075517a9497a80d39c495ba6b44f3982c7371129b89e2
 F ext/session/sessionmem.test f2a735db84a3e9e19f571033b725b0b2daf847f3f28b1da55a0c1a4e74f1de09
 F ext/session/sessionnoop.test a9366a36a95ef85f8a3687856ebef46983df399541174cb1ede2ee53b8011bc7
 F ext/session/sessionrebase.test ccfa716b23bd1d3b03217ee58cfd90c78d4b99f53e6a9a2f05e82363b9142810
+F ext/session/sessionsize.test 32ce42e9fed589276ef072b68c6f325e54ef7ef67c37ccd3ec8c822dd997f3c7
 F ext/session/sessionstat1.test 218d351cf9fcd6648f125a26b607b140310160184723c2666091b54450a68fb5
 F ext/session/sessionwor.test 6fd9a2256442cebde5b2284936ae9e0d54bde692d0f5fd009ecef8511f4cf3fc
-F ext/session/sqlite3session.c a7c5ac1acfe21d94b37921b29b0458d64d022a66b282338eee4aafa9c018cb1c
-F ext/session/sqlite3session.h f48662626e7a3176a188787a0bd360933dd46cccd98df01c208b02051c540fb7
-F ext/session/test_session.c 90ccf1c30c857bd2fb3f6c990163e8f389ddbdbdc7fa5baa2f6f5f287df41c08
+F ext/session/sqlite3session.c b205b57eecfb93aee23653ba4b07be6930afaa3760317c22ad9872a0bc451d3f
+F ext/session/sqlite3session.h 7d05ae78d03f778bf13f8160595b263d9436260137a8f50c78dc956f4d5121e2
+F ext/session/test_session.c b3d03f73b73d3794007392cf5a9bc27d1a2d3e970d500ab52026c726fa528142
 F ext/userauth/sqlite3userauth.h 7f3ea8c4686db8e40b0a0e7a8e0b00fac13aa7a3
 F ext/userauth/user-auth.txt e6641021a9210364665fe625d067617d03f27b04
 F ext/userauth/userauth.c 7f00cded7dcaa5d47f54539b290a43d2e59f4b1eb5f447545fa865f002fc80cb
@@ -544,7 +545,7 @@ F src/resolve.c e299d53c4077fc32bc63741b5b27fdf8a1328cb8e812b9fafb55441c4c73a80a
 F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
 F src/select.c bc08a79364ad2056b1b3b83142b1cc4eacabf850603166f3a72581d56c320d9c
 F src/shell.c.in 9320b476fde0f7c46700e5695b69b435f1e46843a1513cdd187ac426cdbee016
-F src/sqlite.h.in 18ec33e32001721fd4e9c4705a24a85dff04956ac2c0a21775058884ba845b09
+F src/sqlite.h.in 372554fcd1e1ed25ba44a316e8abdaad712470b7dcfa185ece54f51b10fbde10
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 61b38c073d5e1e96a3d45271b257aef27d0d13da2bea5347692ae579475cd95e
 F src/sqliteInt.h 234ab17b1797cbc2adb7741a15786edf72bc96d40b4de68795e91926cfd46eba
@@ -614,12 +615,12 @@ F src/upsert.c df8f1727d62b5987c4fd302cd4d7c0c84ae57cd65683c5a34a740dfe24039235
 F src/utf.c ee39565f0843775cc2c81135751ddd93eceb91a673ea2c57f61c76f288b041a0
 F src/util.c 41c7a72da1df47864faa378a1c720b38adb288c6838cb6be5594511b6287a048
 F src/vacuum.c 492422c1463c076473bae1858799c7a0a5fe87a133d1223239447c422cd26286
-F src/vdbe.c 045088321542f47419b30be7088137097a9a80946e8eee163899d3ab3d5d9312
+F src/vdbe.c ff3ccdd969774e6ce821b54d076286c84137e2f0e6387b1133bafbaa7470f749
 F src/vdbe.h 25dabb25c7e157b84e59260cfb5b466c3ac103ede9f36f4db371332c47601abe
-F src/vdbeInt.h 000d9ab1ea4cb55a80de15e28f3f595645b4fddef34bca4347fb3db8031d9041
-F src/vdbeapi.c 4a43e303ec3354c785f453e881521969378e85628278ab74ba4a9df790c0d93b
-F src/vdbeaux.c 1ffaf15d48b1678dfd403c02ee60061c10a5dd447051860e793cd3393ab019fe
-F src/vdbeblob.c 37d627ef71aca9a11b3c4063b3d7f1a5f14c4364f9abded40016e37bf15ba392
+F src/vdbeInt.h 58980223a32495ad059d10581b83e133abdc77248b1bab85c080cab8a13bd819
+F src/vdbeapi.c d9e99daf59fec928986838b3389a7337e82fec6b3b5de30206cb99fb4661b94e
+F src/vdbeaux.c 065a10392378109f08435bd50d03dff315e384cde2831d6b8dbaec05f33b10af
+F src/vdbeblob.c c6b8db50b227f66fb404215732068df76485b5b433e5f9d4d9ac27410b218193
 F src/vdbemem.c 947f2a65910edb4014dc981d33e414a68c51f169f9df8c4c493a0ba840b6eb1f
 F src/vdbesort.c f5b5e473a7cee44e47a94817b042fd7172cf3aa2c0a7928a8339d612bcfdec5a
 F src/vdbetrace.c 666c6fd9f1b62be6999e072a45b913e3c2c3518bc60dfd4d54fe304130acb724
@@ -1913,7 +1914,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 8b54102a00852b72783b5b2f336c7a093adbdc8e1b94d46b7d315ae6e5d9476b
-R 164f9f0b95c7a15d85aa81eeb6367354
-U drh
-Z 7326b988597bb541d036316f91b93fa0
+P 6fe50dcc239d2d1fc2a38aa705f4c75cbe26b3e48d098537306d96d6a4005659
+R e870b873cf49a44c733c175dd8b4c0b8
+T *branch * session-changeset-size
+T *sym-session-changeset-size *
+T -sym-trunk *
+U dan
+Z c5add95d4af95f7f7d5a36a6c86b17cc
diff --git a/manifest.uuid b/manifest.uuid
index 9dac01beae..3de85455ce 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-6fe50dcc239d2d1fc2a38aa705f4c75cbe26b3e48d098537306d96d6a4005659
\ No newline at end of file
+b5564a6fd54875db1de884fdc0e5eeabcd6aa5595ad03a8a60843503e830a2d8
\ No newline at end of file
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 9085dc882a..56f23f2b08 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -9546,6 +9546,15 @@ int sqlite3_db_cacheflush(sqlite3*);
 ** triggers; or 2 for changes resulting from triggers called by top-level
 ** triggers; and so forth.
 **
+** When the [sqlite3_blob_write()] API is used to update a blob column,
+** the pre-update hook is invoked with SQLITE_DELETE. This is because the
+** in this case the new values are not available. In this case, when a
+** callback made with op==SQLITE_DELETE is actuall a write using the
+** sqlite3_blob_write() API, the [sqlite3_preupdate_blobwrite()] returns
+** the index of the column being written. In other cases, where the
+** pre-update hook is being invoked for some other reason, including a
+** regular DELETE, sqlite3_preupdate_blobwrite() returns -1.
+**
 ** See also:  [sqlite3_update_hook()]
 */
 #if defined(SQLITE_ENABLE_PREUPDATE_HOOK)
@@ -9566,6 +9575,7 @@ int sqlite3_preupdate_old(sqlite3 *, int, sqlite3_value **);
 int sqlite3_preupdate_count(sqlite3 *);
 int sqlite3_preupdate_depth(sqlite3 *);
 int sqlite3_preupdate_new(sqlite3 *, int, sqlite3_value **);
+int sqlite3_preupdate_blobwrite(sqlite3 *);
 #endif
 
 /*
diff --git a/src/vdbe.c b/src/vdbe.c
index cb4e5ea8d3..c34ea72453 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -5080,7 +5080,7 @@ case OP_Insert: {
   /* Invoke the pre-update hook, if any */
   if( pTab ){
     if( db->xPreUpdateCallback && !(pOp->p5 & OPFLAG_ISUPDATE) ){
-      sqlite3VdbePreUpdateHook(p, pC, SQLITE_INSERT, zDb, pTab, x.nKey,pOp->p2);
+      sqlite3VdbePreUpdateHook(p,pC,SQLITE_INSERT,zDb,pTab,x.nKey,pOp->p2,-1);
     }
     if( db->xUpdateCallback==0 || pTab->aCol==0 ){
       /* Prevent post-update hook from running in cases when it should not */
@@ -5240,7 +5240,7 @@ case OP_Delete: {
     sqlite3VdbePreUpdateHook(p, pC,
         (opflags & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_DELETE, 
         zDb, pTab, pC->movetoTarget,
-        pOp->p3
+        pOp->p3, -1
     );
   }
   if( opflags & OPFLAG_ISNOOP ) break;
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
index cb423f20a1..5e3e523f92 100644
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -472,6 +472,7 @@ struct PreUpdate {
   UnpackedRecord *pUnpacked;      /* Unpacked version of aRecord[] */
   UnpackedRecord *pNewUnpacked;   /* Unpacked version of new.* record */
   int iNewReg;                    /* Register for new.* values */
+  int iBlobWrite;                 /* Value returned by preupdate_blobwrite() */
   i64 iKey1;                      /* First key value passed to hook */
   i64 iKey2;                      /* Second key value passed to hook */
   Mem *aNew;                      /* Array of new.* values */
@@ -560,7 +561,8 @@ void sqlite3VdbeFrameMemDel(void*);      /* Destructor on Mem */
 void sqlite3VdbeFrameDelete(VdbeFrame*); /* Actually deletes the Frame */
 int sqlite3VdbeFrameRestore(VdbeFrame *);
 #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
-void sqlite3VdbePreUpdateHook(Vdbe*,VdbeCursor*,int,const char*,Table*,i64,int);
+void sqlite3VdbePreUpdateHook(
+    Vdbe*,VdbeCursor*,int,const char*,Table*,i64,int,int);
 #endif
 int sqlite3VdbeTransferError(Vdbe *p);
 
diff --git a/src/vdbeapi.c b/src/vdbeapi.c
index ba3bdf6a5f..b21634dc80 100644
--- a/src/vdbeapi.c
+++ b/src/vdbeapi.c
@@ -1905,6 +1905,17 @@ int sqlite3_preupdate_depth(sqlite3 *db){
 }
 #endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
 
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** This function is designed to be called from within a pre-update callback
+** only. 
+*/
+int sqlite3_preupdate_blobwrite(sqlite3 *db){
+  PreUpdate *p = db->pPreUpdate;
+  return (p ? p->iBlobWrite : -1);
+}
+#endif
+
 #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
 /*
 ** This function is called from within a pre-update callback to retrieve
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 296408064f..d22a6a5592 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -5189,7 +5189,8 @@ void sqlite3VdbePreUpdateHook(
   const char *zDb,                /* Database name */
   Table *pTab,                    /* Modified table */
   i64 iKey1,                      /* Initial key value */
-  int iReg                        /* Register for new.* record */
+  int iReg,                       /* Register for new.* record */
+  int iBlobWrite
 ){
   sqlite3 *db = v->db;
   i64 iKey2;
@@ -5225,6 +5226,7 @@ void sqlite3VdbePreUpdateHook(
   preupdate.iKey1 = iKey1;
   preupdate.iKey2 = iKey2;
   preupdate.pTab = pTab;
+  preupdate.iBlobWrite = iBlobWrite;
 
   db->pPreUpdate = &preupdate;
   db->xPreUpdateCallback(db->pPreUpdateArg, db, op, zDb, zTbl, iKey1, iKey2);
diff --git a/src/vdbeblob.c b/src/vdbeblob.c
index 47e3497dd0..a4e79bf89b 100644
--- a/src/vdbeblob.c
+++ b/src/vdbeblob.c
@@ -420,7 +420,7 @@ static int blobReadWrite(
       sqlite3_int64 iKey;
       iKey = sqlite3BtreeIntegerKey(p->pCsr);
       sqlite3VdbePreUpdateHook(
-          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1
+          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1, p->iCol
       );
     }
 #endif