Experimental "PRAGMA secure_delete=FAST" pragma. The intent is to overwrite

deleted content with zeros without increasing the amount of disk I/O.

FossilOrigin-Name: f1682f0faf1a93ded066464b1ddd5f987e21ee0f6bb5e828ed31c3ad903cf2c3

diff --git a/manifest b/manifest
index 7ff1732e8e88c0639097563de72cb5aa1f5e1b41..bf0d4f677ad42d66fde9993fe83788b25e250136 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\smissing\scomma\sin\sthe\sprevious\scheck-in.
-D 2017-06-17T18:49:50.823
+C Experimental\s"PRAGMA\ssecure_delete=FAST"\spragma.\s\sThe\sintent\sis\sto\soverwrite\ndeleted\scontent\swith\szeros\swithout\sincreasing\sthe\samount\sof\sdisk\sI/O.
+D 2017-06-19T11:44:22.399
 F Makefile.in 1cc758ce3374a32425e4d130c2fe7b026b20de5b8843243de75f087c0a2661fb
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 8eeb80162074004e906b53d7340a12a14c471a83743aab975947e95ce061efcc
@@ -348,9 +348,9 @@ F src/auth.c 79f96c6f33bf0e5da8d1c282cee5ebb1852bb8a6ccca3e485d7c459b035d9c3c
 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
-F src/btree.c 430e34151e6ef37e42d3f956bb062907c80ff91e1380704b967b8c1a02a98f64
+F src/btree.c 127ae15b6328376fa549a2ead30a3ec20db31fe991a287c42cf394965f55fff0
 F src/btree.h 3edc5329bc59534d2d15b4f069a9f54b779a7e51289e98fa481ae3c0e526a5ca
-F src/btreeInt.h a392d353104b4add58b4a59cb185f5d5693dde832c565b77d8d4c343ed98f610
+F src/btreeInt.h 97700795edf8a43245720414798b7b29d8e465aef46bf301ffacd431910c0da1
 F src/build.c 88a8cdc11d1c081ed565aa3e795bdf9160f4556463b4c4555e9860b59dd80340
 F src/callback.c 2e76147783386374bf01b227f752c81ec872d730
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
@@ -398,7 +398,7 @@ F src/parse.y 0513387ce02fea97897d8caef82d45f347818593f24f1bdc48e0c530a8af122d
 F src/pcache.c 62835bed959e2914edd26afadfecce29ece0e870
 F src/pcache.h 521bb9610d38ef17a3cc9b5ddafd4546c2ea67fa3d0e464823d73c2a28d50e11
 F src/pcache1.c 1195a21fe28e223e024f900b2011e80df53793f0356a24caace4188b098540dc
-F src/pragma.c 2362670a9d28b71708aecb2b9b10b3f7be71f4c950961c07e81dc400e3ce6371
+F src/pragma.c b5483eba1898652d330231164c17624a93e7a991b2f5c7e8a80f9d85528b308c
 F src/pragma.h 37a1311d0388db480388d7ec09054f7103045eff20d4971f8a433b77f40b9921
 F src/prepare.c b1140c3d0cf59bc85ace00ce363153041b424b7a
 F src/printf.c 8757834f1b54dae512fb25eb1acc8e94a0d15dd2290b58f2563f65973265adb2
@@ -1583,7 +1583,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 9a443397a6b110f60cae32e1f758914d72931e16ddb423e4d4a119df526bf340
-R 48cf46cf5e03c592f1eb729aae9e27b1
+P f3db02f49073c3f08c3fd7816d85e5472d5e22df20d862fe4886eb2a97efb15f
+R bfe3d3db972c98c6ca95dc686a1c98c9
+T *branch * fast-secure-delete
+T *sym-fast-secure-delete *
+T -sym-trunk *
 U drh
-Z 1075564756c6da5b66b28900b7b4b32b
+Z 1665a7b13a5f9ef4377c01699ae7453e

diff --git a/manifest.uuid b/manifest.uuid
index 64f264fc2cb847b7aae965028c98bbcde65bd1a6..d384d6edc59be56808ea092b7582efef1b868373 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-f3db02f49073c3f08c3fd7816d85e5472d5e22df20d862fe4886eb2a97efb15f
\ No newline at end of file
+f1682f0faf1a93ded066464b1ddd5f987e21ee0f6bb5e828ed31c3ad903cf2c3
\ No newline at end of file

diff --git a/src/btree.c b/src/btree.c
index 1f06e4503105a5af0d998d6c85d7d39bb3f7379d..05fea69050cfd9d0a917cb69595bd5842619ca28 100644 (file)
--- a/src/btree.c
+++ b/src/btree.c
@@ -1640,7 +1640,7 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
 
   /* Overwrite deleted information with zeros when the secure_delete
   ** option is enabled */
-  if( pPage->pBt->btsFlags & BTS_SECURE_DELETE ){
+  if( pPage->pBt->btsFlags & BTS_FAST_SECURE ){
     memset(&data[iStart], 0, iSize);
   }
 
@@ -1931,7 +1931,7 @@ static void zeroPage(MemPage *pPage, int flags){
   assert( sqlite3PagerGetData(pPage->pDbPage) == data );
   assert( sqlite3PagerIswriteable(pPage->pDbPage) );
   assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pBt->btsFlags & BTS_SECURE_DELETE ){
+  if( pBt->btsFlags & BTS_FAST_SECURE ){
     memset(&data[hdr], 0, pBt->usableSize - hdr);
   }
   data[hdr] = (char)flags;
@@ -2354,8 +2354,10 @@ int sqlite3BtreeOpen(
     pBt->pCursor = 0;
     pBt->pPage1 = 0;
     if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
-#ifdef SQLITE_SECURE_DELETE
+#if defined(SQLITE_SECURE_DELETE)
     pBt->btsFlags |= BTS_SECURE_DELETE;
+#elif defined(SQLITE_FAST_SECURE_DELETE)
+    pBt->btsFlags |= BTS_OVERWRITE;
 #endif
     /* EVIDENCE-OF: R-51873-39618 The page size for a database file is
     ** determined by the 2-byte integer located at an offset of 16 bytes from
@@ -2803,19 +2805,34 @@ int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
 }
 
 /*
-** Set the BTS_SECURE_DELETE flag if newFlag is 0 or 1.  If newFlag is -1,
-** then make no changes.  Always return the value of the BTS_SECURE_DELETE
-** setting after the change.
+** Change the values for the BTS_SECURE_DELETE and BTS_OVERWRITE flags:
+**
+**    newFlag==0       Both BTS_SECURE_DELETE and BTS_OVERWRITE are cleared
+**    newFlag==1       BTS_SECURE_DELETE set and BTS_OVERWRITE is cleared
+**    newFlag==2       BTS_SECURE_DELETE cleared and BTS_OVERWRITE is set
+**    newFlag==(-1)    No changes
+**
+** This routine acts as a query if newFlag is less than zero
+**
+** With BTS_OVERWRITE set, deleted content is overwritten by zeros, but
+** freelist leaf pages are not written back to the database.  Thus in-page
+** deleted content is cleared, but freelist deleted content is not.
+**
+** With BTS_SECURE_DELETE, operation is like BTS_OVERWRITE with the addition
+** that freelist leaf pages are written back into the database, increasing
+** the amount of disk I/O.
 */
 int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
   int b;
   if( p==0 ) return 0;
   sqlite3BtreeEnter(p);
+  assert( BTS_OVERWRITE==BTS_SECURE_DELETE*2 );
+  assert( BTS_FAST_SECURE==(BTS_OVERWRITE|BTS_SECURE_DELETE) );
   if( newFlag>=0 ){
-    p->pBt->btsFlags &= ~BTS_SECURE_DELETE;
-    if( newFlag ) p->pBt->btsFlags |= BTS_SECURE_DELETE;
-  } 
-  b = (p->pBt->btsFlags & BTS_SECURE_DELETE)!=0;
+    p->pBt->btsFlags &= ~BTS_FAST_SECURE;
+    p->pBt->btsFlags |= BTS_SECURE_DELETE*newFlag;
+  }
+  b = (p->pBt->btsFlags & BTS_FAST_SECURE)/BTS_SECURE_DELETE;
   sqlite3BtreeLeave(p);
   return b;
 }
@@ -7210,7 +7227,7 @@ static int balance_nonroot(
       ** In this case, temporarily copy the cell into the aOvflSpace[]
       ** buffer. It will be copied out again as soon as the aSpace[] buffer
       ** is allocated.  */
-      if( pBt->btsFlags & BTS_SECURE_DELETE ){
+      if( pBt->btsFlags & BTS_FAST_SECURE ){
         int iOff;
 
         iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);

diff --git a/src/btreeInt.h b/src/btreeInt.h
index 47de58f509ce3df1b12100986f2de978fd7be9a3..77069783c757e30f08bc69b7a757b7a72d6b737e 100644 (file)
--- a/src/btreeInt.h
+++ b/src/btreeInt.h
@@ -448,10 +448,12 @@ struct BtShared {
 #define BTS_READ_ONLY        0x0001   /* Underlying file is readonly */
 #define BTS_PAGESIZE_FIXED   0x0002   /* Page size can no longer be changed */
 #define BTS_SECURE_DELETE    0x0004   /* PRAGMA secure_delete is enabled */
-#define BTS_INITIALLY_EMPTY  0x0008   /* Database was empty at trans start */
-#define BTS_NO_WAL           0x0010   /* Do not open write-ahead-log files */
-#define BTS_EXCLUSIVE        0x0020   /* pWriter has an exclusive lock */
-#define BTS_PENDING          0x0040   /* Waiting for read-locks to clear */
+#define BTS_OVERWRITE        0x0008   /* Overwrite deleted content with zeros */
+#define BTS_FAST_SECURE      0x000c   /* Combination of the previous two */
+#define BTS_INITIALLY_EMPTY  0x0010   /* Database was empty at trans start */
+#define BTS_NO_WAL           0x0020   /* Do not open write-ahead-log files */
+#define BTS_EXCLUSIVE        0x0040   /* pWriter has an exclusive lock */
+#define BTS_PENDING          0x0080   /* Waiting for read-locks to clear */
 
 /*
 ** An instance of the following structure is used to hold information

diff --git a/src/pragma.c b/src/pragma.c
index 945fd2d4a7447764ad6c40441df9caf57f2ba3a3..6ab65670106f98d1ba264deee3ff26cf155cc211 100644 (file)
--- a/src/pragma.c
+++ b/src/pragma.c
@@ -515,18 +515,22 @@ void sqlite3Pragma(
 
   /*
   **  PRAGMA [schema.]secure_delete
-  **  PRAGMA [schema.]secure_delete=ON/OFF
+  **  PRAGMA [schema.]secure_delete=ON/OFF/FAST
   **
   ** The first form reports the current setting for the
   ** secure_delete flag.  The second form changes the secure_delete
-  ** flag setting and reports thenew value.
+  ** flag setting and reports the new value.
   */
   case PragTyp_SECURE_DELETE: {
     Btree *pBt = pDb->pBt;
     int b = -1;
     assert( pBt!=0 );
     if( zRight ){
-      b = sqlite3GetBoolean(zRight, 0);
+      if( sqlite3_stricmp(zRight, "fast")==0 ){
+        b = 2;
+      }else{
+        b = sqlite3GetBoolean(zRight, 0);
+      }
     }
     if( pId2->n==0 && b>=0 ){
       int ii;