Changeset 27298 for main/trunk

Timestamp:

2013-05-06T14:18:28+12:00 (11 years ago)

Author:

jmt12

Message:

Add hidden support for the new experimental multiple reader/writer functionality available in SQLite

File:

• main/trunk/greenstone2/perllib/dbutil/sqlite.pm (modified) (3 diffs)

main/trunk/greenstone2/perllib/dbutil/sqlite.pm

@@ -37 +37 @@
 my $db_fast = 0;
 
+# Set to 1 to enable Write Ahead Logging - which is supposed to allow multiple
+# readers/writers on a SQLite database (incompatible with db_fast). From SQLite
+# 3.7 onwards, WAL offers limited parallel reader/writer support but is limited
+# to single computers (doesn't work over networked filesystems). For details
+# see: http://www.sqlite.org/draft/wal.html [jmt12]
+my $db_wal = 0;
 
 # -----------------------------------------------------------------------------
@@ -60 +66 @@
   # to the web page first, as part of the web page's headers, thus ruining the web page
   # which causes an Internal Server Error (500). Therefore, we redirect sqlite's output to
-  # the nul device instead. 
+  # the nul device instead.
+  # using WAL mode (which also changes the journal) suffers a similar issue [jmt12]
   my $nul_device="";
-  if(defined $db_fast && $db_fast == 1) {
+  if($db_fast == 1 || $db_wal == 1) {
     if($ENV{'GSDLOS'} =~ m/windows/) {
         $nul_device=">NUL";
@@ -85 +92 @@
     print $infodb_handle "PRAGMA journal_mode=MEMORY;\n";
   }
-  
+  # Allow parallel readers/writers by using a Write Ahead Logger
+  elsif ($db_wal)
+  {
+    print $infodb_handle "PRAGMA journal_mode=WAL;\n";
+  }
+
   # This is very important for efficiency, otherwise each command will be actioned one at a time
   print $infodb_handle "BEGIN TRANSACTION;\n";