Add Database#error_info on PostgreSQL 9.3+ if pg-0.16.0+ is used, to …

…get a hash of metadata for a given database exception

This just attempts to offer a simpler interface to the underlying
ruby-pg error metadata extraction methods.

CHANGELOG

@@ -1,5 +1,7 @@
 === HEAD
 
+* Add Database#error_info on PostgreSQL 9.3+ if pg-0.16.0+ is used, to get a hash of metadata for a given database exception (jeremyevans)
+
 * Allow prepared_statements plugin to work with instance_filters and update_primary_key plugins (jeremyevans)
 
 * Support deferrable exclusion constraints on PostgreSQL using the :deferrable option (mfoody) (#687)

lib/sequel/adapters/postgres.rb

@@ -276,6 +276,31 @@ def disconnect_connection(conn)
         rescue PGError, IOError
         end
       end
+
+      if SEQUEL_POSTGRES_USES_PG && Object.const_defined?(:PG) && ::PG.const_defined?(:Constants) && ::PG::Constants.const_defined?(:PG_DIAG_SCHEMA_NAME)
+        # Return a hash of information about the related PGError (or Sequel::DatabaseError that
+        # wraps a PGError), with the following entries:
+        #
+        # :schema :: The schema name related to the error
+        # :table :: The table name related to the error
+        # :column :: the column name related to the error
+        # :constraint :: The constraint name related to the error
+        # :type :: The datatype name related to the error
+        #
+        # This requires a PostgreSQL 9.3+ server and 9.3+ client library,
+        # and ruby-pg 0.16.0+ to be supported.
+        def error_info(e)
+          e = e.wrapped_exception if e.is_a?(DatabaseError)
+          r = e.result
+          h = {}
+          h[:schema] = r.error_field(::PG::PG_DIAG_SCHEMA_NAME)
+          h[:table] = r.error_field(::PG::PG_DIAG_TABLE_NAME)
+          h[:column] = r.error_field(::PG::PG_DIAG_COLUMN_NAME)
+          h[:constraint] = r.error_field(::PG::PG_DIAG_CONSTRAINT_NAME)
+          h[:type] = r.error_field(::PG::PG_DIAG_DATATYPE_NAME)
+          h
+        end
+      end
 
       # Execute the given SQL with the given args on an available connection.
       def execute(sql, opts=OPTS, &block)

spec/adapters/postgres_spec.rb

@@ -243,6 +243,33 @@ def logger.method_missing(m, msg)
     end.should raise_error(Sequel::Postgres::ExclusionConstraintViolation)
   end if DB.server_version >= 90000
 
+  specify "should support Database#error_info for getting info hash on the given error" do
+    @db.create_table!(:atest){Integer :t; Integer :t2, :null=>false, :default=>1; constraint :f, :t=>0}
+    begin
+      @db[:atest].insert(1)
+    rescue => e
+    end
+    e.should_not be_nil
+    info = @db.error_info(e)
+    info[:schema].should == 'public'
+    info[:table].should == 'atest'
+    info[:constraint].should == 'f'
+    info[:column].should be_nil
+    info[:type].should be_nil
+
+    begin
+      @db[:atest].insert(0, nil)
+    rescue => e
+    end
+    e.should_not be_nil
+    info = @db.error_info(e.wrapped_exception)
+    info[:schema].should == 'public'
+    info[:table].should == 'atest'
+    info[:constraint].should be_nil
+    info[:column].should == 't2'
+    info[:type].should be_nil
+  end if DB.server_version >= 90300 && DB.adapter_scheme == :postgres && SEQUEL_POSTGRES_USES_PG && Object.const_defined?(:PG) && ::PG.const_defined?(:Constants) && ::PG::Constants.const_defined?(:PG_DIAG_SCHEMA_NAME)
+
   specify "should support Database#do for executing anonymous code blocks" do
     @db.drop_table?(:btest)
     @db.do "BEGIN EXECUTE 'CREATE TABLE btest (a INTEGER)'; EXECUTE 'INSERT INTO btest VALUES (1)'; END"