From 7bec505e26ab86cc9663f9c384956a3df6e3dc54 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Sun, 6 Feb 2005 02:45:41 +0000
Subject: [PATCH] Add the (highly experimental) omit_readlock pragma that
 disables the use of readlocks on read-only databases that are connected using
 ATTACH. (CVS 2317)

FossilOrigin-Name: 2155448d2128119f74241da0ea07d6713b71765c
---
 manifest        | 30 +++++++++++++++---------------
 manifest.uuid   |  2 +-
 src/btree.c     |  5 ++---
 src/btree.h     |  8 ++++++--
 src/main.c      |  5 ++++-
 src/pager.c     | 22 ++++++++++++++--------
 src/pager.h     | 12 ++++++++++--
 src/pragma.c    |  3 ++-
 src/sqliteInt.h |  4 +++-
 src/test2.c     |  4 ++--
 tool/lempar.c   | 12 ++++++++++++
 11 files changed, 71 insertions(+), 36 deletions(-)

diff --git a/manifest b/manifest
index 883e6f931a..8a1bf2f3ae 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Allow\sexpressions\s(including\svariables)\sin\sLIMIT\sand\sOFFSET\sclauses.\sTicket\s#1096.\s(CVS\s2316)
-D 2005-02-05T12:48:48
+C Add\sthe\s(highly\sexperimental)\somit_readlock\spragma\sthat\sdisables\sthe\suse\r\nof\sreadlocks\son\sread-only\sdatabases\sthat\sare\sconnected\susing\sATTACH.\s(CVS\s2317)
+D 2005-02-06T02:45:42
 F Makefile.in d928187101fa3d78426cf48ca30e39d0fb714e57
 F Makefile.linux-gcc a9e5a0d309fa7c38e7c14d3ecf7690879d3a5457
 F README a01693e454a00cc117967e3f9fdab2d4d52e9bc1
@@ -29,8 +29,8 @@ F sqlite3.def dbaeb20c153e1d366e8f421b55a573f5dfc00863
 F sqlite3.pc.in 985b9bf34192a549d7d370e0f0b6b34a4f61369a
 F src/attach.c f78f76bc6a8e5e487ca53636e21ccba2484a9a61
 F src/auth.c 18c5a0befe20f3a58a41e3ddd78f372faeeefe1f
-F src/btree.c c3241d44d44e75b54a249bc7c9ed46c7295dfb2a
-F src/btree.h 74d19cf40ab49fd69abe9e4e12a6c321ad86c497
+F src/btree.c d88766f8eb98241cd7af6aabf302ed322606057b
+F src/btree.h 2e2cc923224649337d7217df0dd32b06673ca180
 F src/build.c fcb437bcda09a57b3fe898dff5ff558e7536621b
 F src/date.c f3d1f5cd1503dabf426a198f3ebef5afbc122a7f
 F src/delete.c 4b94395b52a8f7785acd71135c2ce54f3f5550b3
@@ -41,7 +41,7 @@ F src/hash.c 2b1b13f7400e179631c83a1be0c664608c8f021f
 F src/hash.h 1b0c445e1c89ff2aaad9b4605ba61375af001e84
 F src/insert.c 6ab596846d52bd63d6227f9128a29e4f5b2cf524
 F src/legacy.c d58ea507bce885298a2c8c3cbb0f4bff5d47830b
-F src/main.c 75e70f15b4e22bf69f84c77fb80d6a8f0b0836eb
+F src/main.c 981099f5f73a71e54b0858b01e03d29b83168f7b
 F src/md5.c 7ae1c39044b95de2f62e066f47bb1deb880a1070
 F src/os.h ae44064dc118b20d39450cb331409a775e8bb1c6
 F src/os_common.h 0e7f428ba0a6c40a61bc56c4e96f493231301b73
@@ -51,20 +51,20 @@ F src/os_unix.c 68d3d32937eee90fe1f50d500d1a4ee826cbe790
 F src/os_unix.h f3097815e041e82e24d92505e1ff61ba24172d13
 F src/os_win.c bddeae1c3299be0fbe47077dd4e98b786a067f71
 F src/os_win.h 41a946bea10f61c158ce8645e7646b29d44f122b
-F src/pager.c d21565d0e844712809140632062a7b72b768fdff
-F src/pager.h 9eba8c53dd91eae7f3f90743b2ee242da02a9862
+F src/pager.c d0c1f41b41d2b56a6fd0e1308a66518872f68ed5
+F src/pager.h 70d496f372163abb6340f474288c4bb9ea962cf7
 F src/parse.y ee046c1ea30425a817285e52fb1993c2f955e766
-F src/pragma.c 572d7dd4f9c9d020ca2967a1c3ec02c3126e9631
+F src/pragma.c 809b95acd9af67297a5f923a1a57d82179e0ad3a
 F src/printf.c 3d20b21cfecadacecac3fb7274e746cb81d3d357
 F src/random.c eff68e3f257e05e81eae6c4d50a51eb88beb4ff3
 F src/select.c 6217e1f72cee7e173b21b252fd42a052f3b4decc
 F src/shell.c 3cb0ef124ed9cd582ce89aec59ff7c659bc6e61b
 F src/sqlite.h.in c85f6bad9ca7de29f505fe886646cfff7df4c55e
-F src/sqliteInt.h 58e9365c0f575ef42973439caf3bbab450ad700b
+F src/sqliteInt.h 5fa59fd8369ec403bbdf35a9b6fbf7f60bd77cdb
 F src/table.c 25b3ff2b39b7d87e8d4a5da0713d68dfc06cbee9
 F src/tclsqlite.c 101994a2c4c0eaa69f1de9bfe4a02167f6049e7d
 F src/test1.c feac8a742aca920c8ab18a43b3208ae3a834fe9d
-F src/test2.c bbc2ecc58ceeab12d1e40970f831b1017524e40d
+F src/test2.c 7f0ef466706ac01414e1136b96e5d8a65cb97545
 F src/test3.c 683e1e3819152ffd35da2f201e507228921148d0
 F src/test4.c 7c6b9fc33dd1f3f93c7f1ee6e5e6d016afa6c1df
 F src/test5.c 64f08b2a50ef371a1bd68ff206829e7b1b9997f5
@@ -210,7 +210,7 @@ F test/view.test 306cc4342eb03c28de1a92c681836189e03e5af9
 F test/where.test ffb790dfda75d977bae7a1f5830351623f76861b
 F tool/diffdb.c 7524b1b5df217c20cd0431f6789851a4e0cb191b
 F tool/lemon.c 4a3b5ccc76d959b8caa5f127d23a7e14d4470b4e
-F tool/lempar.c 9bf2f402ab464d3ffb67e7de6154eb66f99d115c
+F tool/lempar.c e8b0eb00a6b905ce2ebd55965ed243574482cd5f
 F tool/memleak.awk 4e7690a51bf3ed757e611273d43fe3f65b510133
 F tool/memleak2.awk 9cc20c8e8f3c675efac71ea0721ee6874a1566e8
 F tool/memleak3.tcl b8eb053190e95a55dc188896afb972e8108822d6
@@ -270,7 +270,7 @@ F www/tclsqlite.tcl e73f8f8e5f20e8277619433f7970060ab01088fc
 F www/vdbe.tcl 095f106d93875c94b47367384ebc870517431618
 F www/version3.tcl 092a01f5ef430d2c4acc0ae558d74c4bb89638a0
 F www/whentouse.tcl 3e522a06ad41992023c80ca29a048ae2331ca5bd
-P a9c33a804d572dd9df15be2029637b10e5a65cc4
-R 0ba525d8e5e37833bac3706da6208349
-U danielk1977
-Z 5a32f92efa7eeaf1966c77064b18ce7a
+P 515e5033a5482f55e7edb66d69ff3da7e234ff2e
+R 46e8e0ae6e4ce5a599c5b024b5c2e241
+U drh
+Z dd83c9ab3e3ce7d0c16a2d058d1f0afb
diff --git a/manifest.uuid b/manifest.uuid
index 78c38d6c49..909087ae42 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-515e5033a5482f55e7edb66d69ff3da7e234ff2e
\ No newline at end of file
+2155448d2128119f74241da0ea07d6713b71765c
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 952e91ad87..4cb6bda99a 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 1.245 2005/02/04 04:07:17 danielk1977 Exp $
+** $Id: btree.c,v 1.246 2005/02/06 02:45:42 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -1223,8 +1223,7 @@ int sqlite3BtreeOpen(
     *ppBtree = 0;
     return SQLITE_NOMEM;
   }
-  rc = sqlite3pager_open(&pBt->pPager, zFilename, EXTRA_SIZE,
-                        (flags & BTREE_OMIT_JOURNAL)==0);
+  rc = sqlite3pager_open(&pBt->pPager, zFilename, EXTRA_SIZE, flags);
   if( rc!=SQLITE_OK ){
     if( pBt->pPager ) sqlite3pager_close(pBt->pPager);
     sqliteFree(pBt);
diff --git a/src/btree.h b/src/btree.h
index 8d78f5871b..7426673537 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 1.61 2005/01/12 07:15:05 danielk1977 Exp $
+** @(#) $Id: btree.h,v 1.62 2005/02/06 02:45:42 drh Exp $
 */
 #ifndef _BTREE_H_
 #define _BTREE_H_
@@ -46,9 +46,13 @@ int sqlite3BtreeOpen(
 
 /* The flags parameter to sqlite3BtreeOpen can be the bitwise or of the
 ** following values.
+**
+** NOTE:  These values must match the corresponding PAGER_ values in
+** pager.h.
 */
 #define BTREE_OMIT_JOURNAL  1  /* Do not use journal.  No argument */
-#define BTREE_MEMORY        2  /* In-memory DB.  No argument */
+#define BTREE_NO_READLOCK   2  /* Omit readlocks on readonly files */
+#define BTREE_MEMORY        4  /* In-memory DB.  No argument */
 
 int sqlite3BtreeClose(Btree*);
 int sqlite3BtreeSetBusyHandler(Btree*,BusyHandler*);
diff --git a/src/main.c b/src/main.c
index 51608cc81e..d36777df9c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -14,7 +14,7 @@
 ** other files are for internal use by SQLite and should not be
 ** accessed by users of the library.
 **
-** $Id: main.c,v 1.279 2005/02/05 07:33:34 danielk1977 Exp $
+** $Id: main.c,v 1.280 2005/02/06 02:45:42 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -858,6 +858,9 @@ int sqlite3BtreeFactory(
   if( omitJournal ){
     btree_flags |= BTREE_OMIT_JOURNAL;
   }
+  if( db->flags & SQLITE_NoReadlock ){
+    btree_flags |= BTREE_NO_READLOCK;
+  }
   if( zFilename==0 ){
 #if TEMP_STORE==0
     /* Do nothing */
diff --git a/src/pager.c b/src/pager.c
index e8b5a14309..53c2b84143 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 1.187 2005/01/29 08:32:45 danielk1977 Exp $
+** @(#) $Id: pager.c,v 1.188 2005/02/06 02:45:42 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -250,6 +250,7 @@ struct Pager {
   u8 journalOpen;             /* True if journal file descriptors is valid */
   u8 journalStarted;          /* True if header of journal is synced */
   u8 useJournal;              /* Use a rollback journal on this file */
+  u8 noReadlock;              /* Do not bother to obtain readlocks */
   u8 stmtOpen;                /* True if the statement subjournal is open */
   u8 stmtInUse;               /* True we are in a statement subtransaction */
   u8 stmtAutoopen;            /* Open stmt journal when main journal is opened*/
@@ -1483,7 +1484,7 @@ int sqlite3pager_open(
   Pager **ppPager,         /* Return the Pager structure here */
   const char *zFilename,   /* Name of the database file to open */
   int nExtra,              /* Extra bytes append to each in-memory page */
-  int useJournal           /* TRUE to use a rollback journal on this file */
+  int flags                /* flags controlling this file */
 ){
   Pager *pPager;
   char *zFullPathname = 0;
@@ -1494,6 +1495,8 @@ int sqlite3pager_open(
   int tempFile = 0;
   int memDb = 0;
   int readOnly = 0;
+  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0;
+  int noReadlock = (flags & PAGER_NO_READLOCK)!=0;
   char zTemp[SQLITE_TEMPNAME_SIZE];
 
   *ppPager = 0;
@@ -1556,6 +1559,7 @@ int sqlite3pager_open(
 #endif
   pPager->journalOpen = 0;
   pPager->useJournal = useJournal && !memDb;
+  pPager->noReadlock = noReadlock && readOnly;
   pPager->stmtOpen = 0;
   pPager->stmtInUse = 0;
   pPager->nRef = 0;
@@ -2144,7 +2148,7 @@ static PgHdr *pager_get_all_dirty_pages(Pager *pPager){
 */
 int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
   PgHdr *pPg;
-  int rc;
+  int rc, n;
 
   /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
   ** number greater than this, or zero, is requested.
@@ -2165,9 +2169,11 @@ int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
   ** on the database file.
   */
   if( pPager->nRef==0 && !MEMDB ){
-    rc = pager_wait_on_lock(pPager, SHARED_LOCK);
-    if( rc!=SQLITE_OK ){
-      return rc;
+    if( !pPager->noReadlock ){
+      rc = pager_wait_on_lock(pPager, SHARED_LOCK);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
     }
 
     /* If a journal file exists, and there is no RESERVED lock on the
@@ -2354,13 +2360,13 @@ int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
     if( pPager->nExtra>0 ){
       memset(PGHDR_TO_EXTRA(pPg, pPager), 0, pPager->nExtra);
     }
-    sqlite3pager_pagecount(pPager);
+    n = sqlite3pager_pagecount(pPager);
     if( pPager->errMask!=0 ){
       sqlite3pager_unref(PGHDR_TO_DATA(pPg));
       rc = pager_errcode(pPager);
       return rc;
     }
-    if( pPager->dbSize<(int)pgno ){
+    if( n<(int)pgno ){
       memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
     }else{
       int rc;
diff --git a/src/pager.h b/src/pager.h
index ef602d3b86..8e88c86eb2 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 1.40 2004/11/05 16:37:03 danielk1977 Exp $
+** @(#) $Id: pager.h,v 1.41 2005/02/06 02:45:42 drh Exp $
 */
 
 /*
@@ -50,13 +50,21 @@ typedef unsigned int Pgno;
 */
 typedef struct Pager Pager;
 
+/*
+** Allowed values for the flags parameter to sqlite3pager_open().
+**
+** NOTE: This values must match the corresponding BTREE_ values in btree.h.
+*/
+#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
+#define PAGER_NO_READLOCK   0x0002    /* Omit readlocks on readonly files */
+
 
 /*
 ** See source code comments for a detailed description of the following
 ** routines:
 */
 int sqlite3pager_open(Pager **ppPager, const char *zFilename,
-                     int nExtra, int useJournal);
+                     int nExtra, int flags);
 void sqlite3pager_set_busyhandler(Pager*, BusyHandler *pBusyHandler);
 void sqlite3pager_set_destructor(Pager*, void(*)(void*,int));
 void sqlite3pager_set_reiniter(Pager*, void(*)(void*,int));
diff --git a/src/pragma.c b/src/pragma.c
index 10accbf916..49a66c12e5 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 1.87 2005/02/04 04:07:17 danielk1977 Exp $
+** $Id: pragma.c,v 1.88 2005/02/06 02:45:42 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -148,6 +148,7 @@ static int flagPragma(Parse *pParse, const char *zLeft, const char *zRight){
     { "empty_result_callbacks",   SQLITE_NullCallback  },
     /* The following is VERY experimental */
     { "writable_schema",          SQLITE_WriteSchema   },
+    { "omit_readlock",            SQLITE_NoReadlock    },
   };
   int i;
   const struct sPragmaType *p;
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index dc4369aae1..627aeae65d 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -11,7 +11,7 @@
 *************************************************************************
 ** Internal interface definitions for SQLite.
 **
-** @(#) $Id: sqliteInt.h,v 1.367 2005/02/05 12:48:48 danielk1977 Exp $
+** @(#) $Id: sqliteInt.h,v 1.368 2005/02/06 02:45:43 drh Exp $
 */
 #ifndef _SQLITEINT_H_
 #define _SQLITEINT_H_
@@ -469,6 +469,8 @@ struct sqlite3 {
 #define SQLITE_SqlTrace       0x00000200  /* Debug print SQL as it executes */
 #define SQLITE_VdbeListing    0x00000400  /* Debug listings of VDBE programs */
 #define SQLITE_WriteSchema    0x00000800  /* OK to update SQLITE_MASTER */
+#define SQLITE_NoReadlock     0x00001000  /* Readlocks are omitted when 
+                                          ** accessing read-only databases */
 
 /*
 ** Possible values for the sqlite.magic field.
diff --git a/src/test2.c b/src/test2.c
index b7c83cf56e..e77f2f2576 100644
--- a/src/test2.c
+++ b/src/test2.c
@@ -13,7 +13,7 @@
 ** is not included in the SQLite library.  It is used for automated
 ** testing of the SQLite library.
 **
-** $Id: test2.c,v 1.28 2005/01/13 11:07:54 danielk1977 Exp $
+** $Id: test2.c,v 1.29 2005/02/06 02:45:43 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -81,7 +81,7 @@ static int pager_open(
     return TCL_ERROR;
   }
   if( Tcl_GetInt(interp, argv[2], &nPage) ) return TCL_ERROR;
-  rc = sqlite3pager_open(&pPager, argv[1], 0, 1);
+  rc = sqlite3pager_open(&pPager, argv[1], 0, 0);
   if( rc!=SQLITE_OK ){
     Tcl_AppendResult(interp, errorName(rc), 0);
     return TCL_ERROR;
diff --git a/tool/lempar.c b/tool/lempar.c
index f7e2471f05..685f952c5f 100644
--- a/tool/lempar.c
+++ b/tool/lempar.c
@@ -462,6 +462,18 @@ static void yy_reduce(
   }
 #endif /* NDEBUG */
 
+#ifndef NDEBUG
+  /* Silence complaints from purify about yygotominor being uninitialized
+  ** in some cases when it is copied into the stack after the following
+  ** switch.  yygotominor is uninitialized when a rule reduces that does
+  ** not set the value of its left-hand side nonterminal.  Leaving the
+  ** value of the nonterminal uninitialized is utterly harmless as long
+  ** as the value is never used.  So really the only thing this code
+  ** accomplishes is to quieten purify.  
+  */
+  memset(&yygotominor, 0, sizeof(yygotominor));
+#endif
+
   switch( yyruleno ){
   /* Beginning here are the reduction cases.  A typical example
   ** follows: