From f8e632b630c57bc61ba6b8ddfdc6ad0ee56d03c6 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Tue, 8 May 2007 14:51:36 +0000
Subject: [PATCH] Add the max_page_count pragma used to limit the maximum size
 of a database file.  Untested. (CVS 3948)

FossilOrigin-Name: b1b74f06688fd90fcaf54cf95e2e7beeb5fc1040
---
 manifest       | 26 +++++++++++++-------------
 manifest.uuid  |  2 +-
 src/btree.c    | 11 ++++++++++-
 src/btree.h    |  3 ++-
 src/limits.h   |  6 +++++-
 src/pager.c    | 31 ++++++++++++++++++++++++-------
 src/pager.h    |  3 ++-
 src/pragma.c   | 23 ++++++++++++++++++++++-
 www/pragma.tcl | 12 +++++++++++-
 9 files changed, 90 insertions(+), 27 deletions(-)

diff --git a/manifest b/manifest
index f715954d86..00b0493fdd 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\spotential\sbuffer\soverrun\sin\sthe\sreplace()\sfunction.\s(CVS\s3947)
-D 2007-05-08T14:39:04
+C Add\sthe\smax_page_count\spragma\sused\sto\slimit\sthe\smaximum\ssize\sof\sa\sdatabase\nfile.\s\sUntested.\s(CVS\s3948)
+D 2007-05-08T14:51:37
 F Makefile.in 87b200ad9970907f76df734d29dff3d294c10935
 F Makefile.linux-gcc 2d8574d1ba75f129aba2019f0b959db380a90935
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -61,8 +61,8 @@ F src/alter.c ca8fc4a3c7359379598dc12589b65c32eb88defd
 F src/analyze.c 4bbf5ddf9680587c6d4917e02e378b6037be3651
 F src/attach.c a674f72b5e4a02b81d0ae7e6e14c1a2f48e36491
 F src/auth.c 902f4722661c796b97f007d9606bd7529c02597f
-F src/btree.c 6d3db6416c71f678a4dd4719ce6d754ad5927c46
-F src/btree.h 845543b5a53d5d8a80ea14aeeb521276602317b7
+F src/btree.c dca996d45f1b8a87c86d0ec22a7ef6ca8c1ab805
+F src/btree.h 8444af0c82c0e878b5ce8a6eb345904830e678a5
 F src/btreeInt.h cb3c0e9eb842d06079a62cdf3492c90c5db7ba75
 F src/build.c 5a60e2e4a21fa8cbdf9e01a95e6d5ca44ff4a2b9
 F src/callback.c 9c12535669a638f90a67e10440b99c7b93c0fbf4
@@ -76,7 +76,7 @@ F src/hash.c 67b23e14f0257b69a3e8aa663e4eeadc1a2b6fd5
 F src/hash.h 1b3f7e2609141fd571f62199fc38687d262e9564
 F src/insert.c e595ca26805dfb3a9ebaabc28e7947c479f3b14d
 F src/legacy.c 388c71ad7fbcd898ba1bcbfc98a3ac954bfa5d01
-F src/limits.h 7275e16d02c0164177e466a1438e174cc1936f8d
+F src/limits.h e8d89699ff06f1492f5ddcf1ec61eab0df623975
 F src/loadext.c afe4f4755dc49c36ef505748bbdddecb9f1d02a2
 F src/main.c 35b340716319e88817493172aa63abe8be13b543
 F src/malloc.c b89e31258a85158d15795bf87ae3ba007e56329b
@@ -92,10 +92,10 @@ F src/os_unix.c cb1fb044b84870c7b1b8b2902e9d7be779f8b7ce
 F src/os_unix.h 5768d56d28240d3fe4537fac08cc85e4fb52279e
 F src/os_win.c 3b6169038101d06c54b4f04662bfd44b6cf2f289
 F src/os_win.h 41a946bea10f61c158ce8645e7646b29d44f122b
-F src/pager.c 9c9a9df78636f4b9c8e18f90e93337a1231aaef7
-F src/pager.h 236e4065b3ca066e8e3edd43fbdd00e2c71a55d5
+F src/pager.c c5b32e741fb73930b6ec3d886ea680a3de3be5f7
+F src/pager.h db31691786504625e7e25c8cde4f40779ba209d9
 F src/parse.y efbca804082366871a11f5f272c17672186961d2
-F src/pragma.c f426fef6b045dec23b1cf2f28397122a50fde109
+F src/pragma.c b881b457170d4922893f59b1caaac98f8e4192e2
 F src/prepare.c c932f4398c3bf66fa366ad676c6f7e8ac5eaf7f6
 F src/printf.c 67de0dcb40ef3297f4a047b434b81585c0f7062d
 F src/random.c 6119474a6f6917f708c1dee25b9a8e519a620e88
@@ -473,7 +473,7 @@ F www/opcode.tcl 5bd68059416b223515a680d410a9f7cb6736485f
 F www/optimizer.tcl d6812a10269bd0d7c488987aac0ad5036cace9dc
 F www/optimizing.tcl f0b2538988d1bbad16cbfe63ec6e8f48c9eb04e5
 F www/optoverview.tcl 815df406a38c9f69b27d37e8f7ede004c6d9f19e
-F www/pragma.tcl 9e5a48dc564fc2c4a1d38501402e6b45c4d3870b
+F www/pragma.tcl 3655b3fff2f6491768e020f43364288f9e149f79
 F www/quickstart.tcl 8708a4ca83fbf55c66af1782992626f20c3df095
 F www/shared.gif 265bae80c5b311c5a86e47662821076ffaf5c6ea
 F www/sharedcache.tcl 3ebec81110e606af6fd65a3c4c19562cb173b29c
@@ -485,7 +485,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl 890248cf7b70e60c383b0e84d77d5132b3ead42b
 F www/whentouse.tcl fc46eae081251c3c181bd79c5faef8195d7991a5
-P c59d436095b5258d7132a432c0cb6cd5a7990d85
-R e45c28784fb5fd22f2c0e733c939e615
-U danielk1977
-Z 3a097658130cbbee5c196715fa819c73
+P b0fb4a3cf6ddbc17ccd0c719b34a720d9090bc93
+R e3726b52936aa8a8c64158a436e46313
+U drh
+Z f695cedfb2999b1238e46a40ecfacacd
diff --git a/manifest.uuid b/manifest.uuid
index 2a7a4c9eab..078c978a55 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-b0fb4a3cf6ddbc17ccd0c719b34a720d9090bc93
\ No newline at end of file
+b1b74f06688fd90fcaf54cf95e2e7beeb5fc1040
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 97cd84a43e..13278a1ca8 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.377 2007/05/05 18:39:25 drh Exp $
+** $Id: btree.c,v 1.378 2007/05/08 14:51:37 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -1332,6 +1332,15 @@ int sqlite3BtreeGetPageSize(Btree *p){
 int sqlite3BtreeGetReserve(Btree *p){
   return p->pBt->pageSize - p->pBt->usableSize;
 }
+
+/*
+** Set the maximum page count for a database if mxPage is positive.
+** No changes are made if mxPage is 0 or negative.
+** Regardless of the value of mxPage, return the maximum page count.
+*/
+int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
+  return sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
+}
 #endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
 
 /*
diff --git a/src/btree.h b/src/btree.h
index 9ebba9d6be..942ee94e0b 100644
--- a/src/btree.h
+++ b/src/btree.h
@@ -13,7 +13,7 @@
 ** subsystem.  See comments in the source code for a detailed description
 ** of what each interface routine does.
 **
-** @(#) $Id: btree.h,v 1.80 2007/05/05 18:49:53 drh Exp $
+** @(#) $Id: btree.h,v 1.81 2007/05/08 14:51:37 drh Exp $
 */
 #ifndef _BTREE_H_
 #define _BTREE_H_
@@ -67,6 +67,7 @@ int sqlite3BtreeSetSafetyLevel(Btree*,int,int);
 int sqlite3BtreeSyncDisabled(Btree*);
 int sqlite3BtreeSetPageSize(Btree*,int,int);
 int sqlite3BtreeGetPageSize(Btree*);
+int sqlite3BtreeMaxPageCount(Btree*,int);
 int sqlite3BtreeGetReserve(Btree*);
 int sqlite3BtreeSetAutoVacuum(Btree *, int);
 int sqlite3BtreeGetAutoVacuum(Btree *);
diff --git a/src/limits.h b/src/limits.h
index 90f289465d..e85ec0dae9 100644
--- a/src/limits.h
+++ b/src/limits.h
@@ -12,7 +12,7 @@
 ** 
 ** This file defines various limits of what SQLite can process.
 **
-** @(#) $Id: limits.h,v 1.2 2007/05/08 13:58:28 drh Exp $
+** @(#) $Id: limits.h,v 1.3 2007/05/08 14:51:37 drh Exp $
 */
 
 /*
@@ -126,6 +126,10 @@
 
 /*
 ** Maximum number of pages in one database file.
+**
+** This is really just the default value for the max_page_count pragma.
+** This value can be lowered (or raised) at run-time using that the
+** max_page_count macro.
 */
 #ifndef SQLITE_MAX_PAGE_COUNT
 # define SQLITE_MAX_PAGE_COUNT 1073741823
diff --git a/src/pager.c b/src/pager.c
index 1226e28de1..383f576451 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -18,7 +18,7 @@
 ** file simultaneously, or one process from reading the database while
 ** another is writing.
 **
-** @(#) $Id: pager.c,v 1.336 2007/05/05 11:48:54 drh Exp $
+** @(#) $Id: pager.c,v 1.337 2007/05/08 14:51:37 drh Exp $
 */
 #ifndef SQLITE_OMIT_DISKIO
 #include "sqliteInt.h"
@@ -256,9 +256,9 @@ struct Pager {
   int nExtra;                 /* Add this many bytes to each in-memory page */
   int pageSize;               /* Number of bytes in a page */
   int nPage;                  /* Total number of in-memory pages */
-  int nMaxPage;               /* High water mark of nPage */
   int nRef;                   /* Number of in-memory pages with PgHdr.nRef>0 */
   int mxPage;                 /* Maximum number of pages to hold in cache */
+  Pgno mxPgno;                /* Maximum allowed size of the database */
   u8 *aInJournal;             /* One bit for each page in the database file */
   u8 *aInStmt;                /* One bit for each page in the database */
   char *zFilename;            /* Name of the database file */
@@ -1751,8 +1751,8 @@ int sqlite3PagerOpen(
   /* pPager->stmtSize = 0; */
   /* pPager->stmtJSize = 0; */
   /* pPager->nPage = 0; */
-  /* pPager->nMaxPage = 0; */
   pPager->mxPage = 100;
+  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
   assert( PAGER_UNLOCK==0 );
   /* pPager->state = PAGER_UNLOCK; */
   /* pPager->errMask = 0; */
@@ -1829,6 +1829,21 @@ int sqlite3PagerSetPagesize(Pager *pPager, int pageSize){
   return pPager->pageSize;
 }
 
+/*
+** Attempt to set the maximum database page count if mxPage is positive. 
+** Make no changes if mxPage is zero or negative.  And never reduce the
+** maximum page count below the current size of the database.
+**
+** Regardless of mxPage, return the current maximum page count.
+*/
+int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
+  if( mxPage>0 ){
+    pPager->mxPgno = mxPage;
+  }
+  sqlite3PagerPagecount(pPager);
+  return pPager->mxPgno;
+}
+
 /*
 ** The following set of routines are used to disable the simulated
 ** I/O error mechanism.  These routines are used to avoid simulated
@@ -1914,6 +1929,9 @@ int sqlite3PagerPagecount(Pager *pPager){
   if( n==(PENDING_BYTE/pPager->pageSize) ){
     n++;
   }
+  if( n>pPager->mxPgno ){
+    pPager->mxPgno = n;
+  }
   return n;
 }
 
@@ -2912,10 +2930,6 @@ static int pagerAllocatePage(Pager *pPager, PgHdr **ppPg){
     pPg->pNextAll = pPager->pAll;
     pPager->pAll = pPg;
     pPager->nPage++;
-    if( pPager->nPage>pPager->nMaxPage ){
-      assert( pPager->nMaxPage==(pPager->nPage-1) );
-      pPager->nMaxPage++;
-    }
   }else{
     /* Recycle an existing page with a zero ref-count. */
     rc = pager_recycle(pPager, 1, &pPg);
@@ -3060,6 +3074,9 @@ int sqlite3PagerAcquire(
     ** file, or by setting the entire page to zero.
     */
     if( nMax<(int)pgno || MEMDB || (noContent && !pPager->alwaysRollback) ){
+      if( pgno>pPager->mxPgno ){
+        return SQLITE_FULL;
+      }
       memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
       pPg->needRead = noContent && !pPager->alwaysRollback;
       IOTRACE(("ZERO %p %d\n", pPager, pgno));
diff --git a/src/pager.h b/src/pager.h
index 59c54255fe..88b8694b4e 100644
--- a/src/pager.h
+++ b/src/pager.h
@@ -13,7 +13,7 @@
 ** subsystem.  The page cache subsystem reads and writes a file a page
 ** at a time and provides a journal for rollback.
 **
-** @(#) $Id: pager.h,v 1.59 2007/05/08 01:08:49 drh Exp $
+** @(#) $Id: pager.h,v 1.60 2007/05/08 14:51:37 drh Exp $
 */
 
 #ifndef _PAGER_H_
@@ -60,6 +60,7 @@ void sqlite3PagerSetBusyhandler(Pager*, BusyHandler *pBusyHandler);
 void sqlite3PagerSetDestructor(Pager*, void(*)(DbPage*,int));
 void sqlite3PagerSetReiniter(Pager*, void(*)(DbPage*,int));
 int sqlite3PagerSetPagesize(Pager*, int);
+int sqlite3PagerMaxPageCount(Pager*, int);
 int sqlite3PagerReadFileheader(Pager*, int, unsigned char*);
 void sqlite3PagerSetCachesize(Pager*, int);
 int sqlite3PagerClose(Pager *pPager);
diff --git a/src/pragma.c b/src/pragma.c
index c329ea8f64..19597d1149 100644
--- a/src/pragma.c
+++ b/src/pragma.c
@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file contains code used to implement the PRAGMA command.
 **
-** $Id: pragma.c,v 1.135 2007/05/08 01:08:49 drh Exp $
+** $Id: pragma.c,v 1.136 2007/05/08 14:51:37 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -344,6 +344,27 @@ void sqlite3Pragma(
     }
   }else
 
+  /*
+  **  PRAGMA [database.]max_page_count
+  **  PRAGMA [database.]max_page_count=N
+  **
+  ** The first form reports the current setting for the
+  ** maximum number of pages in the database file.  The 
+  ** second form attempts to change this setting.  Both
+  ** forms return the current setting.
+  */
+  if( sqlite3StrICmp(zLeft,"max_page_count")==0 ){
+    Btree *pBt = pDb->pBt;
+    int newMax = 0;
+    if( zRight ){
+      newMax = atoi(zRight);
+    }
+    if( pBt ){
+      newMax = sqlite3BtreeMaxPageCount(pBt, newMax);
+    }
+    returnSingleInt(pParse, "max_page_count", newMax);
+  }else
+
   /*
   **  PRAGMA [database.]locking_mode
   **  PRAGMA [database.]locking_mode = (normal|exclusive)
diff --git a/www/pragma.tcl b/www/pragma.tcl
index 13b4f4f41f..781bfadc92 100644
--- a/www/pragma.tcl
+++ b/www/pragma.tcl
@@ -1,7 +1,7 @@
 #
 # Run this Tcl script to generate the pragma.html file.
 #
-set rcsid {$Id: pragma.tcl,v 1.23 2007/05/04 19:16:30 drh Exp $}
+set rcsid {$Id: pragma.tcl,v 1.24 2007/05/08 14:51:37 drh Exp $}
 source common.tcl
 header {Pragma statements supported by SQLite}
 
@@ -339,6 +339,16 @@ PRAGMA <b>main.</b>locking_mode=EXCLUSIVE;
     </p>
 </li>
 
+<a name="pragma_max_page_count"></a>
+<li><p><b>PRAGMA max_page_count;
+       <br>PRAGMA max_page_count = </b><i>N</i><b>;</b></p>
+    <p>Query or set the maximum number of pages in the database file.
+    Both forms of the pragma return the maximum page count.  The second
+    form attempts to modify the maximum page count.  The maximum page
+    count cannot be reduced below the current database size.
+    </p>
+</li>
+
 <a name="pragma_read_uncommitted"></a>
 <li><p><b>PRAGMA read_uncommitted;
        <br>PRAGMA read_uncommitted = </b><i>0 | 1</i><b>;</b></p>