Clarify some comments. No changes to code. (CVS 5049)

FossilOrigin-Name: 7f80539225b17a62e4aa09e6d514e3e9e1b22c36

2 files changed, 22 insertions, 3 deletions

diff --git a/src/pager.c b/src/pager.c
index 6c6fca4c5..bf7da6c93 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 1.434 2008/04/24 12:37:40 danielk1977 Exp $
+** @(#) $Id: pager.c,v 1.435 2008/04/25 12:25:42 drh Exp $
 */
 #ifndef SQLITE_OMIT_DISKIO
 #include "sqliteInt.h"
@@ -3084,6 +3084,15 @@ static PgHdr *pager_get_all_dirty_pages(Pager *pPager){
 ** database with the same name.  Just delete the journal.
 **
 ** Return negative if unable to determine the status of the journal.
+**
+** This routine does not open the journal file to examine its
+** content.  Hence, the journal might contain the name of a master
+** journal file that has been deleted, and hence not be hot.  Or
+** the header of the journal might be zeroed out.  This routine
+** does not discover these cases of a non-hot journal - if the
+** journal file exists and is not empty this routine assumes it
+** is hot.  The pager_playback() routine will discover that the
+** journal file is not really hot and will no-op.
 */
 static int hasHotJournal(Pager *pPager){
   sqlite3_vfs *pVfs = pPager->pVfs;
diff --git a/src/vdbe.c b/src/vdbe.c
index 43eab1b23..78183fcfa 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.734 2008/04/24 19:15:11 shane Exp $
+** $Id: vdbe.c,v 1.735 2008/04/25 12:25:42 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -2268,11 +2268,21 @@ case OP_MakeRecord: {
 /* Opcode: Statement P1 * * * *
 **
 ** Begin an individual statement transaction which is part of a larger
-** BEGIN..COMMIT transaction.  This is needed so that the statement
+** transaction.  This is needed so that the statement
 ** can be rolled back after an error without having to roll back the
 ** entire transaction.  The statement transaction will automatically
 ** commit when the VDBE halts.
 **
+** If the database connection is currently in autocommit mode (that 
+** is to say, if it is in between BEGIN and COMMIT)
+** and if there are no other active statements on the same database
+** connection, then this operation is a no-op.  No statement transaction
+** is needed since any error can use the normal ROLLBACK process to
+** undo changes.
+**
+** If a statement transaction is started, then a statement journal file
+** will be allocated and initialized.
+**
 ** The statement is begun on the database file with index P1.  The main
 ** database file has an index of 0 and the file used for temporary tables
 ** has an index of 1.