Add some simple tests and fixes for shared-schema locking. (CVS 2869)

FossilOrigin-Name: d054bed15aee3edef93cc84c83be443cdd489946

manifest

@@ -1,5 +1,5 @@
-C Back\sout\sthe\saddition\sof\sthe\snew\sheader\sfile\s-\sbad\sidea.\s(CVS\s2868)
-D 2006-01-06T12:03:19
+C Add\ssome\ssimple\stests\sand\sfixes\sfor\sshared-schema\slocking.\s(CVS\s2869)
+D 2006-01-06T13:00:29
 F Makefile.in 131285a3e97597dd7ed3eb23a1010c7d0685ae41
 F Makefile.linux-gcc aee18d8a05546dcf1888bd4547e442008a49a092
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -34,8 +34,8 @@ F src/alter.c e9deb3f4fd7c663a0d1f235d541bc5ea1f2cfa8b
 F src/analyze.c d821684cdb4d0403e327e4a3440a832e9e54fa3a
 F src/attach.c 999104c56a60b88eab11ef9c8f40dedf1650b287
 F src/auth.c cdec356a5cd8b217c346f816c5912221537fe87f
-F src/btree.c d1402f4e1cfc500b31d13990f36dd8d3d27443bc
-F src/btree.h 96b8c00c6e11ff92f8d3d6a7a0ff358bd10d8f19
+F src/btree.c f34c1e8d93003cbd8cc579865e0c0db4f595b97e
+F src/btree.h f7ba8e2f9f387cca4978e1495504a0bf556dcbf2
 F src/build.c 715ac7d49bbfcae5f3fdfd60885397b2133c283b
 F src/callback.c 62066afd516f220575e81b1a1239ab92a2eae252
 F src/complete.c df1681cef40dec33a286006981845f87b194e7a4
@@ -63,7 +63,7 @@ F src/pager.c 07509ddb478f5a70f9ff53607ab8a44456c22811
 F src/pager.h e0acb095b3ad0bca48f2ab00c87346665643f64f
 F src/parse.y 58258759fabdd48f1d2561e276097290b1ea2680
 F src/pragma.c 4af4041a88d41421b8ff2e5574d82d7b9d1e35b1
-F src/prepare.c 67ff283f7c71e32a91d8c843e758eb4bf68ab94e
+F src/prepare.c 48baea211104dfcfa59857a32d62c934f63a15ed
 F src/printf.c f47a2f4b5387cd2ebb12e9117a1a5d6bd9a2b812
 F src/random.c ff5e9a8cad790e2a51cd4d2e7737dc8540e09d1d
 F src/select.c a60e5c7fad9ce7adc78d9eb32a0a89dd5acd04fb
@@ -222,7 +222,7 @@ F test/select4.test c239f516aa31f42f2ef7c6d7cd01105f08f934ca
 F test/select5.test 07a90ab3c7e3f0a241a9cdea1d997b2c8a89ff0b
 F test/select6.test f459a19bdac0501c4d3eb1a4df4b7a76f1bb8ad4
 F test/select7.test 1bf795b948c133a15a2a5e99d3270e652ec58ce6
-F test/shared.test ee5a4154d257e4c2ce1ae418783b87847473de90
+F test/shared.test eb6b9ac456f60ed485b9ca5873d563abacae815a
 F test/sort.test 0e4456e729e5a92a625907c63dcdedfbe72c5dc5
 F test/subquery.test e6de53332c0301b3cfa34edc3f3cd5fa1e859efd
 F test/subselect.test 2d13fb7f450db3595adcdd24079a0dd1d2d6abc2
@@ -328,7 +328,7 @@ F www/optimizing.tcl f0b2538988d1bbad16cbfe63ec6e8f48c9eb04e5
 F www/optoverview.tcl 815df406a38c9f69b27d37e8f7ede004c6d9f19e
 F www/pragma.tcl 44f7b665ca598ad24724f35991653638a36a6e3f
 F www/quickstart.tcl 2f3daf8038e82a102e1e8cc877aafa7a413f5f11
-F www/sharedcache.tcl c42098d1436bcb54ec7f08d07c2e75316e2dde68
+F www/sharedcache.tcl 884a93bf0f814204b24959c0c6229d61dd4734cc
 F www/speed.tcl 656ed5be8cc9d536353e1a96927b925634a62933
 F www/sqlite.tcl a883ed7b47371d31d471e6aea5ed1f972ae8e1be
 F www/support.tcl 7961ce16290692578d783bb11f0dc8391a9be9c3
@@ -337,7 +337,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 752a2754879becc32da9f9b910f3330f8c7145e4
-R 77860345776bf3dbb42b93b9296c48b1
-U drh
-Z 246dc71f2673d21c26bf8f1421f9f9ff
+P 0c4c45c36fe1c3c2980155ef5126a2ad53100d65
+R c892910cec71c19aeb323bc85b1a92ea
+U danielk1977
+Z 5e6321921a4935029ecd84d938104014

manifest.uuid

@@ -1 +1 @@
-0c4c45c36fe1c3c2980155ef5126a2ad53100d65
+d054bed15aee3edef93cc84c83be443cdd489946

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.281 2006/01/06 06:33:12 danielk1977 Exp $
+** $Id: btree.c,v 1.282 2006/01/06 13:00:29 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -601,7 +601,7 @@ static int restoreCursorPosition(BtCursor *pCur, int doSeek){
 ** Query to see if btree handle p may obtain a lock of type eLock 
 ** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
 ** SQLITE_OK if the lock may be obtained (by calling lockTable()), or
-** SQLITE_BUSY if not.
+** SQLITE_LOCKED if not.
 */
 static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
   BtShared *pBt = p->pBt;
@@ -635,7 +635,7 @@ static int queryTableLock(Btree *p, Pgno iTab, u8 eLock){
     for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
       if( pIter->pBtree!=p && pIter->iTable==iTab && 
           (pIter->eLock!=eLock || eLock!=READ_LOCK) ){
-        return SQLITE_BUSY;
+        return SQLITE_LOCKED;
       }
     }
   }
@@ -6484,6 +6484,14 @@ void *sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
   return pBt->pSchema;
 }
 
+/*
+** Return true if another user of the same shared btree as the argument
+** handle holds an exclusive lock on the sqlite_master table.
+*/
+int sqlite3BtreeSchemaLocked(Btree *p){
+  return (queryTableLock(p, MASTER_ROOT, READ_LOCK)!=SQLITE_OK);
+}
+
 #ifndef SQLITE_OMIT_SHARED_CACHE
 /*
 ** Enable the shared pager and schema features.

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 1.67 2006/01/05 11:34:34 danielk1977 Exp $
+** @(#) $Id: btree.h,v 1.68 2006/01/06 13:00:30 danielk1977 Exp $
 */
 #ifndef _BTREE_H_
 #define _BTREE_H_
@@ -77,6 +77,7 @@ int sqlite3BtreeIsInTrans(Btree*);
 int sqlite3BtreeIsInStmt(Btree*);
 int sqlite3BtreeSync(Btree*, const char *zMaster);
 void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
+int sqlite3BtreeSchemaLocked(Btree *);
 
 const char *sqlite3BtreeGetFilename(Btree *);
 const char *sqlite3BtreeGetDirname(Btree *);

src/prepare.c

@@ -13,7 +13,7 @@
 ** interface, and routines that contribute to loading the database schema
 ** from disk.
 **
-** $Id: prepare.c,v 1.13 2006/01/05 11:34:34 danielk1977 Exp $
+** $Id: prepare.c,v 1.14 2006/01/06 13:00:30 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -436,8 +436,9 @@ int sqlite3_prepare(
   Parse sParse;
   char *zErrMsg = 0;
   int rc = SQLITE_OK;
+  int i;
 
-  assert(!sqlite3Tsd()->mallocFailed);
+  assert( !sqlite3Tsd()->mallocFailed );
 
   assert( ppStmt );
   *ppStmt = 0;
@@ -445,6 +446,19 @@ int sqlite3_prepare(
     return SQLITE_MISUSE;
   }
 
+  /* If any attached database schemas are locked, do not proceed with
+  ** compilation. Instead return SQLITE_LOCKED immediately.
+  */
+  for(i=0; i<db->nDb; i++) {
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt && sqlite3BtreeSchemaLocked(pBt) ){
+      const char *zDb = db->aDb[i].zName;
+      sqlite3Error(db, SQLITE_LOCKED, "database schema is locked: %s", zDb);
+      sqlite3SafetyOff(db);
+      return SQLITE_LOCKED;
+    }
+  }
+  
   memset(&sParse, 0, sizeof(sParse));
   sParse.db = db;
   sqlite3RunParser(&sParse, zSql, &zErrMsg);
@@ -524,7 +538,7 @@ int sqlite3_prepare16(
   ** tricky bit is figuring out the pointer to return in *pzTail.
   */
   char *zSql8 = 0;
-  char *zTail8 = 0;
+  const char *zTail8 = 0;
   int rc;
 
   if( sqlite3SafetyCheck(db) ){

test/shared.test

@@ -11,7 +11,7 @@
 # This file implements regression tests for SQLite library.  The
 # focus of this file is testing the SELECT statement.
 #
-# $Id: shared.test,v 1.3 2006/01/06 06:33:13 danielk1977 Exp $
+# $Id: shared.test,v 1.4 2006/01/06 13:00:30 danielk1977 Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -73,7 +73,7 @@ do_test shared-1.4 {
   catchsql {
     INSERT INTO abc VALUES(4, 5, 6);
   } db2
-} {1 {database is locked}}
+} {1 {database table is locked}}
 do_test shared-1.5 {
   # Using connection 2 (the one without the open transaction), try to create
   # a new table. This should fail because of the open read transaction 
@@ -81,7 +81,7 @@ do_test shared-1.5 {
   catchsql {
     CREATE TABLE def(d, e, f);
   } db2
-} {1 {database is locked}}
+} {1 {database table is locked}}
 do_test shared-1.6 {
   # Upgrade connection 1's transaction to a write transaction. Create
   # a new table - def - and insert a row into it. Because the connection 1
@@ -104,7 +104,7 @@ do_test shared-1.7 {
   catchsql {
     SELECT * FROM sqlite_master;
   } db2
-} {1 {database is locked}}
+} {1 {database schema is locked: main}}
 do_test shared-1.8 {
   # Commit the connection 1 transaction.
   execsql {
@@ -133,7 +133,7 @@ do_test shared-2.2 {
   catchsql {
     INSERT INTO abc VALUES(1, 2, 3);
   } db2
-} {1 {database is locked}}
+} {1 {database table is locked}}
 do_test shared-2.3 {
   # Turn db's transaction into a write-transaction. db3 should still be
   # able to read from table def (but will not see the new row). Connection
@@ -157,7 +157,7 @@ do_test shared-2.3 {
   ] [
     catchsql { SELECT * FROM def; } db2
   ]
-} {0 {IV V VI} 1 {database is locked}}
+} {0 {IV V VI} 1 {database table is locked}}
 do_test shared-2.4 {
   # Commit the open transaction on db. db2 still holds a read-transaction.
   # This should prevent db3 from writing to the database, but not from 
@@ -257,10 +257,16 @@ do_test shared-4.1.3 {
   set sqlite_open_file_count
 } {2}
 
+# Sanity check: Create a table in ./test.db via handle db, and test that handle
+# db2 can "see" the new table immediately. A handle using a seperate pager
+# cache would have to reload the database schema before this were possible.
+#
 do_test shared-4.2.1 {
   execsql {
     CREATE TABLE abc(a, b, c);
+    CREATE TABLE def(d, e, f);
     INSERT INTO abc VALUES('i', 'ii', 'iii');
+    INSERT INTO def VALUES('I', 'II', 'III');
   }
 } {}
 do_test shared-4.2.2 {
@@ -269,6 +275,91 @@ do_test shared-4.2.2 {
   } db2
 } {i ii iii}
 
+# Open a read-transaction and read from table abc via handle 2. Check that
+# handle 1 can read table abc. Check that handle 1 cannot modify table abc
+# or the database schema. Then check that handle 1 can modify table def.
+#
+do_test shared-4.3.1 {
+  execsql {
+    BEGIN;
+    SELECT * FROM test.abc;
+  } db2
+} {i ii iii}
+do_test shared-4.3.2 {
+  catchsql {
+    INSERT INTO abc VALUES('iv', 'v', 'vi');
+  }
+} {1 {database table is locked}}
+do_test shared-4.3.3 {
+  catchsql {
+    CREATE TABLE ghi(g, h, i);
+  }
+} {1 {database table is locked}}
+do_test shared-4.3.3 {
+  catchsql {
+    INSERT INTO def VALUES('IV', 'V', 'VI');
+  }
+} {0 {}}
+do_test shared-4.3.4 {
+  # Cleanup: commit the transaction opened by db2.
+  execsql {
+    COMMIT
+  } db2
+} {}
+
+# Open a write-transaction using handle 1 and modify the database schema.
+# Then try to execute a compiled statement to read from the same 
+# database via handle 2 (fails to get the lock on sqlite_master). Also
+# try to compile a read of the same database using handle 2 (also fails).
+# Finally, compile a read of the other database using handle 2. This
+# should also fail.
+#
+do_test shared-4.4.1.2 {
+  # Sanity check 1: Check that the schema is what we think it is when viewed
+  # via handle 1.
+  execsql {
+    CREATE TABLE test2.ghi(g, h, i);
+    SELECT 'test.db:'||name FROM sqlite_master 
+    UNION ALL
+    SELECT 'test2.db:'||name FROM test2.sqlite_master;
+  }
+} {test.db:abc test.db:def test2.db:ghi}
+do_test shared-4.4.1.2 {
+  # Sanity check 2: Check that the schema is what we think it is when viewed
+  # via handle 2.
+  execsql {
+    SELECT 'test2.db:'||name FROM sqlite_master 
+    UNION ALL
+    SELECT 'test.db:'||name FROM test.sqlite_master;
+  } db2
+} {test2.db:ghi test.db:abc test.db:def}
+
+do_test shared-4.4.2 {
+  set ::DB2 [sqlite3_connection_pointer db2]
+  set sql {SELECT * FROM abc}
+  set ::STMT1 [sqlite3_prepare $::DB2 $sql -1 DUMMY]
+  execsql {
+    BEGIN;
+    CREATE TABLE jkl(j, k, l);
+  }
+  sqlite3_step $::STMT1
+} {SQLITE_ERROR}
+do_test shared-4.4.3 {
+  sqlite3_finalize $::STMT1
+} {SQLITE_LOCKED}
+do_test shared-4.4.4 {
+  set rc [catch {
+    set ::STMT1 [sqlite3_prepare $::DB2 $sql -1 DUMMY]
+  } msg]
+  list $rc $msg
+} {1 {(6) database schema is locked: test}}
+do_test shared-4.4.5 {
+  set rc [catch {
+    set ::STMT1 [sqlite3_prepare $::DB2 "SELECT * FROM ghi" -1 DUMMY]
+  } msg]
+  list $rc $msg
+} {1 {(6) database schema is locked: test}}
+
 catch {db2 close}
 catch {db close}
 

www/sharedcache.tcl

@@ -120,12 +120,9 @@ read-lock, write-lock or no lock on each database table.
 or a single active write lock. To read data a table, a connection must 
 first obtain a read-lock. To write to a table, a connection must obtain a 
 write-lock on that table. If a required table lock cannot be obtained,
-the query fails and SQLITE_BUSY is returned to the caller.
+the query fails and SQLITE_LOCKED is returned to the caller.
 </p> 
 
-<p><b>TODO: Should we be invoking the busy-handler here? Just waiting won't do
-any good, but something else might...  </b></p>
-
 <p>Once a connection obtains a table lock, it is not released until the
 current transaction (read or write) is concluded.
 </p>
@@ -181,12 +178,32 @@ accessing any database tables or obtaining any other read or write locks.</li>
 a CREATE or DROP TABLE statement), a connection must obtain a write-lock on 
 <i>sqlite_master</i>.
 </li>
-<li>A connection may not compile an SQL statement that refers to database
-tables if any other connection is holding a write-lock on <i>sqlite_master</i>.
+<li>A connection may not compile an SQL statement if any other connection
+is holding a write-lock on the <i>sqlite_master</i> table of any attached
+database (including the default database, "main"). 
 </li>
 </ul>
 }
 
+HEADING 3 {Schema locking and attached databases}
+
+puts {
+<p>The final point in the bullet list is deceptively complicated when
+multiple databases are attached to connections. Exactly when is access to a 
+specific database schema "required" to compile a statement? The way in
+which SQLite resolves the names of schema objects (i.e. tables, indices, 
+triggers and views) depends on whether or not the name was qualified
+or unqualified in the original SQL statement. The first statement below
+uses a qualified table name, the second uses an unqualified table name.
+Both refer to the same underlying table.
+</p>
+<pre>
+    SELECT name FROM main.sqlite_master;
+    SELECT name FROM sqlite_master;
+</pre>
+1
+}
+
 HEADING 1 {Thread Related Issues}
 
 puts {