Improvements to the way that truncation is implemented in sqlite_dbpage().

FossilOrigin-Name: ac4bb2e4ecf0bdb0d8ac12b1ccb42d51af02f519a038cfc79faab5c216971056

manifest

@@ -1,5 +1,5 @@
-C Update\sthe\sbuild\sinstructions\sfor\sWindows\sto\snote\sthat\sVS2015\sor\slater\sis\nrequired\sto\savoid\sthe\sneed\sto\sinstall\stclsh.exe.
+C Improvements\sto\sthe\sway\sthat\struncation\sis\simplemented\sin\ssqlite_dbpage().
-D 2025-01-02T12:14:01.327
+D 2025-01-02T15:03:13.323
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
@@ -724,7 +724,7 @@ F src/callback.c db3a45e376deff6a16c0058163fe0ae2b73a2945f3f408ca32cf74960b28d49
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c d35723024b963edce9c0fad5b3303e8bb9266083784844baed10a6dedfe26f3b
 F src/date.c 89ce1ff20512a7fa5070ba6e7dd5c171148ca7d580955795bf97c79c2456144a
-F src/dbpage.c b1aeb47c1004f26c39c6800f0045b8d729d232aca24f6aa430c491b83003d033
+F src/dbpage.c cfa9ed0a490bd2e07e4cdba68503ccd5e587dcb4ac9c7ae9ed382a9cd924f29b
 F src/dbstat.c 73362c0df0f40ad5523a6f5501224959d0976757b511299bf892313e79d14f5c
 F src/delete.c 03a77ba20e54f0f42ebd8eddf15411ed6bdb06a2c472ac4b6b336521bf7cea42
 F src/expr.c 3329173aacc6c37da3971b6253827799b32e301673be00126df8271bf018e15f
@@ -1076,8 +1076,8 @@ F test/dbfuzz.c 73047c920d6210e5912c87cdffd9a1c281d4252e
 F test/dbfuzz001.test 6c9a4622029d69dc38926f115864b055cb2f39badd25ec22cbfb130c8ba8e9c3
 F test/dbfuzz2-seed1.db e6225c6f3d7b63f9c5b6867146a5f329d997ab105bee64644dc2b3a2f2aebaee
 F test/dbfuzz2.c 4b3c12de4d98b1b2d908ab03d217d4619e47c8b23d5e67f8a6f2b1bdee7cae23
-F test/dbpage.test fce29035c7566fd7835ec0f19422cb4b9c6944ce0e1b936ff8452443f92e887d
+F test/dbpage.test dba7b6048c461125595278bd838e66d01bba67d8ad1da94489a7851439e8fa86
-F test/dbpagefault.test 35f06cfb2ef100a9b19d25754e8141b9cba9b7daabd4c60fa5af93fcce884435
+F test/dbpagefault.test ea39de2ca86041a9c6df1135645180a76d0a8da93ac159e2fafe38e39636530b
 F test/dbstatus.test 4a4221a883025ffd39696b3d1b3910b928fb097d77e671351acb35f3aed42759
 F test/dbstatus2.test f5fe0afed3fa45e57cfa70d1147606c20d2ba23feac78e9a172f2fe8ab5b78ef
 F test/decimal.test ef731887b43ee32ef86e1c8fddb61a40789f988332c029c601dcf2c319277e9e
@@ -2204,8 +2204,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 4f6c36a61c2b27e204c00bd7467453098f756c7e596b7e62d47da8784fbd2026
+P da0ef0567be55648413bcbf2e129f348776a908dbad2ac8582ee3e27ac459e3b
-R c359455d12a83b16327a4eb96d1245c3
+R 963301e91789659974012d48c99b5d2d
 U drh
-Z 5fb03700b1eda71764ba1102db353cb9
+Z dc0b704adc2bca53154303a0d3643971
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-da0ef0567be55648413bcbf2e129f348776a908dbad2ac8582ee3e27ac459e3b
+ac4bb2e4ecf0bdb0d8ac12b1ccb42d51af02f519a038cfc79faab5c216971056

src/dbpage.c

@@ -317,6 +317,24 @@ static int dbpageRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
   return SQLITE_OK;
 }
 
+/* 
+** Open write transactions. Since we do not know in advance which database
+** files will be written by the sqlite_dbpage virtual table, start a write
+** transaction on them all.
+**
+** Return SQLITE_OK if successful, or an SQLite error code otherwise.
+*/
+static int dbpageBeginTrans(DbpageTable *pTab){
+  sqlite3 *db = pTab->db;
+  int rc = SQLITE_OK;
+  int i;
+  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ) rc = sqlite3BtreeBeginTrans(pBt, 1, 0);
+  }
+  return rc;
+}
+
 static int dbpageUpdate(
   sqlite3_vtab *pVtab,
   int argc,
@@ -384,6 +402,12 @@ static int dbpageUpdate(
       goto update_fail;
     }
   }
+
+  if( dbpageBeginTrans(pTab)!=SQLITE_OK ){
+    zErr = "failed to open transaction";
+    goto update_fail;
+  }
+
   pPager = sqlite3BtreePager(pBt);
   rc = sqlite3PagerGet(pPager, pgno, (DbPage**)&pDbPage, 0);
   if( rc==SQLITE_OK ){
@@ -405,18 +429,8 @@ update_fail:
   return SQLITE_ERROR;
 }
 
-/* Since we do not know in advance which database files will be
-** written by the sqlite_dbpage virtual table, start a write transaction
-** on them all.
-*/
 static int dbpageBegin(sqlite3_vtab *pVtab){
   DbpageTable *pTab = (DbpageTable *)pVtab;
-  sqlite3 *db = pTab->db;
-  int i;
-  for(i=0; i<db->nDb; i++){
-    Btree *pBt = db->aDb[i].pBt;
-    if( pBt ) (void)sqlite3BtreeBeginTrans(pBt, 1, 0);
-  }
   pTab->pgnoTrunc = 0;
   return SQLITE_OK;
 }
@@ -474,7 +488,7 @@ int sqlite3DbpageRegister(sqlite3 *db){
     0,                            /* xRename */
     0,                            /* xSavepoint */
     0,                            /* xRelease */
-    dbpageRollbackTo,             /* xRollbackTo */
+    0/*dbpageRollbackTo*/,             /* xRollbackTo */
     0,                            /* xShadowName */
     0                             /* xIntegrity */
   };

test/dbpage.test

@@ -108,4 +108,96 @@ do_execsql_test 300 {
   SELECT * FROM sqlite_temp_schema, sqlite_dbpage;
 } {}
 
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 400 {
+  ATTACH ':memory:' AS aux1;
+  BEGIN;
+    CREATE VIRTUAL TABLE aux1.t1 USING sqlite_dbpage;
+    INSERT INTO t1 VALUES(17, NULL);
+  COMMIT;
+}
+
+#-------------------------------------------------------------------------
+reset_db
+forcedelete test.db2
+sqlite3 db2 test.db2
+db2 eval {
+  CREATE TABLE t1(x, y);
+}
+
+do_execsql_test 500 {
+  CREATE TABLE x1(a);
+  INSERT INTO x1 VALUES( hex(randomblob(2000)) );
+  INSERT INTO x1 VALUES( hex(randomblob(2000)) );
+  INSERT INTO x1 VALUES( hex(randomblob(2000)) );
+  INSERT INTO x1 VALUES( hex(randomblob(2000)) );
+  PRAGMA page_count;
+} {18}
+
+do_test 510 {
+  db eval  BEGIN 
+  db2 eval { PRAGMA page_count } {
+    db eval {
+      INSERT INTO sqlite_dbpage values($page_count, NULL);
+    }
+  }
+  db2 eval { SELECT pgno, data FROM sqlite_dbpage } {
+    db eval {
+      INSERT INTO sqlite_dbpage values($pgno, $data);
+    }
+  }
+
+  db eval COMMIT
+} {}
+
+db close
+sqlite3 db test.db
+
+do_execsql_test 520 {
+  PRAGMA page_count;
+  SELECT * FROM t1;
+} {2}
+
+#-------------------------------------------------------------------------
+reset_db
+forcedelete test.db2
+do_execsql_test 610 {
+  ATTACH 'test.db2' AS aux;
+  CREATE TABLE t1(x);
+  CREATE TABLE t2(y);
+  INSERT INTO t1 VALUES(1234);
+  CREATE TABLE aux.x1(z);
+}
+
+set pgno [db one {SELECT max(rootpage) FROM sqlite_schema}]
+sqlite3 db2 test.db2
+db2 eval {
+  BEGIN;
+    SELECT * FROM x1;
+}
+
+do_catchsql_test 620 {
+  UPDATE sqlite_dbpage SET data = (
+    SELECT data FROM sqlite_dbpage WHERE pgno=$pgno-1
+  ) WHERE pgno = $pgno;
+} {1 {database is locked}}
+
+db2 eval {
+  COMMIT;
+}
+
+do_catchsql_test 630 {
+  UPDATE sqlite_dbpage SET data = (
+    SELECT data FROM sqlite_dbpage WHERE pgno=$pgno-1
+  ) WHERE pgno = $pgno;
+} {0 {}}
+
+db close
+sqlite3 db test.db
+
+do_execsql_test 640 {
+  SELECT * FROM t2;
+} {1234}
+
 finish_test

test/dbpagefault.test

@@ -82,5 +82,31 @@ do_catchsql_test 3.2 {
 #  faultsim_test_result {0 {}}
 #}
 
+reset_db
+forcedelete test.db2
+do_execsql_test 4.0 {
+  CREATE TABLE t1(x);
+  INSERT INTO t1 VALUES('one');
+  CREATE TABLE t2(x);
+  INSERT INTO t2 VALUES('two');
+  ATTACH 'test.db2' AS aux;
+  CREATE TABLE aux.x1(x);
+}
+
+set pgno [db one {SELECT max(rootpage) FROM sqlite_schema}]
+
+faultsim_save_and_close
+do_faultsim_test 4 -prep {
+  faultsim_restore_and_reopen
+  execsql { ATTACH 'test.db2' AS aux; }
+} -body {
+  execsql { 
+    UPDATE sqlite_dbpage SET data = (
+      SELECT data FROM sqlite_dbpage WHERE pgno=($pgno-1)
+    ) WHERE pgno = $pgno;
+  }
+} -test {
+  faultsim_test_result {0 {}} {1 {unable to open a temporary database file for storing temporary tables}}
+}
 
 finish_test