From: Ash Berlin <ash_github@firemirror.com>
Date: Thu, 31 Jan 2008 11:37:09 +0000 (+0000)
Subject: Document significance of preproces_schema method
X-Git-Tag: v0.11008~345
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=934e1b39156523c2bcf1d4de8f426458df864f01;p=dbsrgits%2FSQL-Translator.git

Document significance of preproces_schema method
---

diff --git a/META.yml b/META.yml
index 06f6236..48dcb35 100644
--- a/META.yml
+++ b/META.yml
@@ -236,7 +236,7 @@ provides:
   Test::SQL::Translator:
     file: lib/Test/SQL/Translator.pm
     version: 1.08
-generated_by: Module::Build version 0.28
+generated_by: Module::Build version 0.2808
 meta-spec:
   url: http://module-build.sourceforge.net/META-spec-v1.2.html
   version: 1.2
diff --git a/lib/SQL/Translator/Diff.pm b/lib/SQL/Translator/Diff.pm
index 3f71bfa..5cbb0b0 100644
--- a/lib/SQL/Translator/Diff.pm
+++ b/lib/SQL/Translator/Diff.pm
@@ -79,8 +79,8 @@ sub compute_differences {
     die $@ if $@;
 
     if (my $preprocess = $producer_class->can('preprocess_schema')) {
-      $producer_class->$preprocess($source_schema);
-      $producer_class->$preprocess($target_schema);
+      $preprocess->($source_schema);
+      $preprocess->($target_schema);
     }
 
     my %src_tables_checked = ();
@@ -482,9 +482,6 @@ thrown.
 
 =item * C<batch_alter_table($table, $hash)> (optional)
 
-
-=back
-
 If the producer supports C<batch_alter_table>, it will be called with the 
 table to alter and a hash, the keys of which will be the method names listed
 above; values will be arrays of fields or constraints to operate on. In the 
@@ -498,11 +495,31 @@ I.e. the hash might look something like the following:
    alter_field => [ [$old_field, $new_field] ]
  }
 
+
+=item * C<preprocess_schema($class, $schema)> (optional)
+
+C<preprocess_schema> is called by the Diff code to allow the producer to
+normalize any data it needs to first. For example, the MySQL producer uses
+this method to ensure that FK contraint names are unique.
+
+Basicaly any changes that need to be made to produce the SQL file for the
+schema should be done here, so that a diff between a parsed SQL file and (say)
+a parsed DBIx::Class::Schema object will be sane.
+
+(As an aside, DBIx::Class, for instance, uses the presence of a 
+C<preprocess_schema> function on the producer to know that it can diff between
+the previous SQL file and its own internal representation. Without this method
+on th producer it will diff the two SQL files which is slower, but known to 
+work better on old-style producers.)
+
+=back
+
+
 =head1 AUTHOR
 
 Original Author(s) unknown.
 
-Refactor and more comprehensive tests by Ash Berlin C<< ash@cpan.org >>.
+Refactor/re-write and more comprehensive tests by Ash Berlin C<< ash@cpan.org >>.
 
 Redevelopment sponsored by Takkle Inc.
 
diff --git a/lib/SQL/Translator/Producer/MySQL.pm b/lib/SQL/Translator/Producer/MySQL.pm
index 4bf2b65..9b65bb7 100644
--- a/lib/SQL/Translator/Producer/MySQL.pm
+++ b/lib/SQL/Translator/Producer/MySQL.pm
@@ -126,7 +126,7 @@ my %translate  = (
 
 
 sub preprocess_schema {
-    my ($class, $schema) = @_;
+    my ($schema) = @_;
 
     # extra->{mysql_table_type} used to be the type. It belongs in options, so
     # move it if we find it. Return Engine type if found in extra or options
@@ -226,7 +226,7 @@ sub produce {
     # \todo Don't set if MySQL 3.x is set on command line
     $create .= "SET foreign_key_checks=0;\n\n";
 
-    __PACKAGE__->preprocess_schema($schema);
+    preprocess_schema($schema);
 
     #
     # Generate sql
diff --git a/lib/SQL/Translator/Producer/SQLite.pm b/lib/SQL/Translator/Producer/SQLite.pm
index 149ba7b..a228653 100644
--- a/lib/SQL/Translator/Producer/SQLite.pm
+++ b/lib/SQL/Translator/Producer/SQLite.pm
@@ -423,6 +423,9 @@ sub rename_table {
 
 }
 
+# No-op. Just here to signify that we are a new style parser.
+sub preproces_schema { }
+
 1;
 
 =pod