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POActiverecord-import & serial column in PostgreSQL
 

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    <p>I am in the process of upgrading a Rails 2.3.4 project to Rails 3.1.1. The old version used ar-extensions to handle a data import. I pulled out ar-extensions and replaced it with activerecord-import, which I understand has exactly the same interfaces.</p> <p>My code calls looks like this</p> <pre><code>Student.import(columns, values) </code></pre> <p>Both args are valid arrays holding the correct data, but I get a big fat error!</p> <p>The error stack looks like this:</p> <pre><code>NoMethodError (You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.split): activerecord (3.1.1) lib/active_record/connection_adapters/postgresql_adapter.rb:828:in 'default_sequence_name' activerecord (3.1.1) lib/active_record/base.rb:647:in `reset_sequence_name' activerecord (3.1.1) lib/active_record/base.rb:643:in `sequence_name' activerecord-import (0.2.9) lib/activerecord-import/import.rb:203:in `import' </code></pre> <p>Looking through the code it seems as though Activerecord-import calls activerecord which in turn looks for the name and next value of the Postgres sequence.</p> <p>So activerecord-import looks for the sequence_name lib/activerecord-import/import.rb:203</p> <pre><code># Force the primary key col into the insert if it's not # on the list and we are using a sequence and stuff a nil # value for it into each row so the sequencer will fire later -&gt; if !column_names.include?(primary_key) &amp;&amp; sequence_name &amp;&amp; connection.prefetch_primary_key? column_names &lt;&lt; primary_key array_of_attributes.each { |a| a &lt;&lt; nil } end </code></pre> <p>It calls active record ... lib/active_record/base.rb:647:in `reset_sequence_name'</p> <pre><code># Lazy-set the sequence name to the connection's default. This method # is only ever called once since set_sequence_name overrides it. def sequence_name #:nodoc: -&gt; reset_sequence_name end def reset_sequence_name #:nodoc: -&gt; default = connection.default_sequence_name(table_name, primary_key) set_sequence_name(default) default end </code></pre> <p>The code errors when <code>serial_sequence</code> returns nil and <code>default_sequence_name</code> tries to split it.</p> <pre><code>lib/active_record/connection_adapters/postgresql_adapter.rb # Returns the sequence name for a table's primary key or some other specified key. def default_sequence_name(table_name, pk = nil) #:nodoc: -&gt; serial_sequence(table_name, pk || 'id').split('.').last rescue ActiveRecord::StatementInvalid "#{table_name}_#{pk || 'id'}_seq" end def serial_sequence(table, column) result = exec_query(&lt;&lt;-eosql, 'SCHEMA', [[nil, table], [nil, column]]) SELECT pg_get_serial_sequence($1, $2) eosql result.rows.first.first end </code></pre> <p>When I execute <code>pg_get_serial_sequence()</code> directly against the database I get no value returned:</p> <pre><code>SELECT pg_get_serial_sequence('student', 'id') </code></pre> <p>But I can see that in the database there is a sequence called <code>student_id_seq</code></p> <p>I am using the following versions of Ruby, rails PG etc..</p> <ul> <li>Rails 3.1.1</li> <li>Ruby 1.9.2</li> <li>Activerecord-import 0.2.9</li> <li>pg 0.12.2</li> <li>psql (9.0.5, server 9.1.3)</li> </ul> <p>I have migrated the database from MySQL to PostgreSQL, I don't think this has any bearing on the problem but I thought that I'd better add it for completeness.</p> <p>I can't work out why this isn't working!</p>
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