begin
  require 'postgres'
rescue Object => ex
  Logger.error 'Ruby-PostgreSQL bindings are not installed!'
  Logger.error ex
end

#--
# Customize to make more compatible with Og.
#++

class PGconn # :nodoc: all
  # Lists all the tables within the database.
  
  def list_tables
    begin
      r = self.exec "SELECT c.relname FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relkind='r' AND n.nspname NOT IN ('pg_catalog', 'pg_toast') AND pg_catalog.pg_table_is_visible(c.oid)"
    rescue Exception
      # Racing
      return []
    end
    ret = r.result.flatten
    r.clear
    ret
  end

  # Returns true if a table exists within the database, false 
  # otherwise.
  
  def table_exists?(table) #rp: this should be abstracted to the sql abstractor
    begin
      r = self.exec "SELECT c.relname FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relkind='r' AND n.nspname NOT IN ('pg_catalog', 'pg_toast') AND pg_catalog.pg_table_is_visible(c.oid) AND c.relname='#{self.class.escape(table.to_s)}'"
    rescue Exception
      return false # Racing...
    end
    ret = r.result.size != 0
    r.clear
    ret
  end

  # Returns the PostgreSQL OID of a table within the database or 
  # nil if it doesn't exist. Mostly for internal usage.
  
  def table_oid(table)
    begin
      r = self.exec "SELECT c.oid FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relkind='r' AND n.nspname NOT IN ('pg_catalog', 'pg_toast') AND pg_catalog.pg_table_is_visible(c.oid) AND c.relname='#{self.class.escape(table.to_s)}'"
    rescue Exception
      return nil # Racing...
    end
    ret = r.result.flatten.first
    r.clear
    ret
  end

  # Returns an array of arrays containing the list of fields within a
  # table. Each element contains two elements, the first is the field
  # name and the second is the field type. Returns nil if the table
  # does not exist.
  
  def table_field_list(table)
    return nil unless pg_oid = table_oid(table)
    r = self.exec "SELECT a.attname, pg_catalog.format_type(a.atttypid, a.atttypmod) FROM pg_catalog.pg_attribute a WHERE a.attrelid = '#{pg_oid}' AND a.attnum > 0 AND NOT a.attisdropped ORDER BY a.attnum"
    ret = r.result
    r.clear
    ret
  end

  # Returns a hash containing the foreign key constrains within a table.
  # The keys are constraint names and the values are the constraint
  # definitions.
  
  def table_foreign_keys(table)
    return nil unless pg_oid = table_oid(table)
    r = self.exec "SELECT conname, pg_catalog.pg_get_constraintdef(oid, true) as condef FROM pg_catalog.pg_constraint r WHERE r.conrelid = '#{pg_oid}' AND r.contype = 'f'"
    res = r.result
    ret = Hash.new
    res.each do |double|
      ret[double.first] = double.last
    end
    r.clear
    ret
  end
  
  # Returns a hash keyed by table (as a string) with each value also
  # being a hash keyed by the constraint name (as a string) and the
  # value being a string that contains the constraint definition.
   
  def all_foreign_keys
    loop_counter = 0
    loop_max = 5
    begin
      r = self.exec "SELECT c.relname,r.conname, pg_catalog.pg_get_constraintdef(r.oid, true) as condef FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace JOIN pg_catalog.pg_constraint r ON r.conrelid = c.oid WHERE c.relkind='r' AND r.contype ='f' AND n.nspname NOT IN ('pg_catalog', 'pg_toast') AND pg_catalog.pg_table_is_visible(c.oid);"
    rescue RuntimeError => ex
      raise unless ex.message =~ /cache lookup failed for relation (\d+)/ # Racing
#      damaged_relation = $1
#      Logger.error "Got damage to #{damaged_relation}"
      loop_counter += 1
      if loop_counter > loop_max
        Logger.error "PostgreSQL had more than #{loop_max} cache errors, your database is almost certainly corrupt as pg_class does not match the PostgreSQL cache. Either use pg_dump to save the data, re-create the database, let og rebuild the schema and use pg_restore to restore the data, or repair it by hand"
        exit
      end
      Logger.error "There is a problem with PostgreSQL's internal cache, retrying... (#{loop_counter} of #{loop_max})"
      # you have a horrible setup anyhow, and it allows your
      # horrible setup to work (deleting tables so fast
      # in parallel PostgreSQL's internal lookups fail)
      sleep 2
      retry
    end
    res = r.result
    ret = Hash.new
    res.each do |tripple|
      ret[tripple.first] ||= Hash.new
      ret[tripple[0]][tripple[1]] = tripple[2]
    end
    r.clear
    ret
  end

end

require 'og/store/sql'

#--
# Customize the standard postgres resultset to make
# more compatible with Og.
#++

class PGresult # :nodoc: all
  def blank?
    0 == num_tuples
  end
  
  def next
    self
  end

  def each_row
    for row in (0...num_tuples)
      yield(self, row)
    end
  end
  
  def first_value
    val = getvalue(0, 0)
    clear
    return val
  end
  
  alias_method :close, :clear
end

module Og

module PsqlUtils
  include SqlUtils
  
  def escape(str)
    return nil unless str
    return PGconn.escape(str.to_s)
  end

  # TODO, mneumann:
  #
  # Blobs are actually a lot faster (and uses up less storage) for large data I
  # think, as they need not to be encoded and decoded. I'd like to have both ;-)
  # BYTEA is easier to handle than BLOBs, but if you implement BLOBs in a way
  # that they are transparent to the user (as I did in Ruby/DBI), I'd prefer that
  # way.
  
  def blob(val)
    val.gsub(/[\000-\037\047\134\177-\377]/) do |b|
      "\\#{ b[0].to_s(8).rjust(3, '0') }" 
    end
  end  
  
  def parse_blob(val)
    return '' unless val
    
    val.gsub(/\\(\\|'|[0-3][0-7][0-7])/) do |s|
      if s.size == 2 then s[1,1] else s[1,3].oct.chr end
    end
  end   
     
end

# A Store that persists objects into a PostgreSQL database.
# To read documentation about the methods, consult the documentation
# for SqlStore and Store.
#
# This is the reference Og store.
# 
# === Design
#
# The getvalue interface is used instead of each for extra
# performance.

class PsqlStore < SqlStore
  extend PsqlUtils
  include PsqlUtils

  def self.create(options)
    # gmosx: system is used to avoid shell expansion.
    system 'createdb', options[:name], '-U', options[:user]
    super
  end

  def self.destroy(options)
    system 'dropdb', options[:name], '-U', options[:user]
    super
  end

  # Purges all tables from the database.
  
  def self.destroy_tables(options)

    conn = PGconn.connect(
      options[:address],
      options[:port], nil, nil,
      options[:name],
      options[:user].to_s,
      options[:password].to_s
    )

    conn.list_tables.each do |table|
      begin
        conn.exec "DROP TABLE #{table} CASCADE"
        Logger.debug "Dropped database table #{table}" if $DBG
      rescue RuntimeError => ex
        catch :ok do # Racing
          throw :ok if ex.message =~ /tuple concurrently updated/
          throw :ok if ex.message =~ /does not exist/          
          throw :ok if ex.message =~ /cache lookup failed/          
          raise
        end
      end
    end

    conn.close
  end


  def initialize(options)
    super
  
    @typemap.update(Og::Blob => 'bytea')

    @conn = PGconn.connect(
      options[:address], 
      options[:port], nil, nil, 
      options[:name], 
      options[:user].to_s, 
      options[:password].to_s
    )
    schema_order = options[:schema_order]
    encoding = options[:encoding]
    min_messages = options[:min_messages]
    
    @conn.exec("SET search_path TO #{schema_order}") if schema_order
    @conn.exec("SET client_encoding TO '#{encoding}'") if encoding
    @conn.exec("SET client_min_messages TO '#{min_messages}'") if min_messages
  rescue => ex
    # gmosx: any idea how to better test this?
    if ex.to_s =~ /database .* does not exist/i
      Logger.info "Database '#{options[:name]}' not found!"
      self.class.create(options)
      retry
    end
    raise
  end

  def close
    @conn.close
    super
  end

  def enchant(klass, manager)
    if klass.schema_inheritance_child?
      klass.const_set 'OGSEQ', "#{table(klass.schema_inheritance_root_class)}_oid_seq"      
    else
      klass.const_set 'OGSEQ', "#{table(klass)}_oid_seq"
    end

    if klass.ann.self.primary_key.symbol == :oid
      unless klass.properties.include? :oid
        klass.property :oid, Fixnum, :sql => 'serial PRIMARY KEY'
      end
    end
    super
  end

  def query(sql)
    Logger.debug sql if $DBG
    return @conn.exec(sql)
  rescue => ex
    handle_sql_exception(ex, sql)
  end

  def exec(sql)
    Logger.debug sql if $DBG
    @conn.exec(sql).clear
  rescue => ex
    handle_sql_exception(ex, sql)
  end

  def sql_update(sql)
    Logger.debug sql if $DBG  
    res = @conn.exec(sql)
    changed = res.cmdtuples
    res.clear
    changed
  end

  # Start a new transaction.

  def start  
    # neumann: works with earlier PSQL databases too.
    exec('BEGIN TRANSACTION') if @transaction_nesting < 1
    @transaction_nesting += 1
  end
  
  # Returns the Og::Manager that owns this store.
  
  def manager
    manager = nil
    ok = false
    ObjectSpace.each_object(Og::Manager) do |manager|
      if manager.store.__id__ == self.__id__
        ok = true
        break
      end
    end
    raise RuntimeError, "#{self.class} could not find it's manager" unless ok
    manager
  end
   
  # Returns an array containing the constraints needed for this relation.
  # The array contains hashes with the format:
  #
  # :table => The name of the table to which the constraint should be
  # applied.
  # :referenced_table => The name of the table which the foreign key
  # refers to.
  # :fk => The name of the field to turn into a foreign key.
  # :pk => The primary key of the referenced table.
  # :update => The action that should be taken if the primary key
  # of a referenced row is changed.
  # :delete => The action that should be taken if a referenced
  # row is deleted.
  # :name => The name of the constraint to apply.
  
  def constraint_info(rel)
    if rel.join_table
      info = join_table_info(rel)
      constraints = [ { :fk => info[:first_key], :referenced_table => info[:first_table], :table => rel.join_table, :pk => ( rel.owner_class.primary_key.field || rel.owner_class.primary_key.symbol ), :update => 'CASCADE', :delete => 'CASCADE'},
        { :fk => info[:second_key], :referenced_table => info[:second_table], :table => rel.join_table, :pk => ( rel.target_class.primary_key.field || rel.target_class.primary_key.symbol ), :update => 'CASCADE', :delete => 'CASCADE' } ]
    elsif rel.class == Og::HasMany
      constraints = [ { :fk => rel.foreign_key, :table => rel.target_class::OGTABLE, :referenced_table => rel.owner_class::OGTABLE, :pk => ( rel.owner_class.primary_key.field || rel.owner_class.primary_key.symbol ), :update => 'SET NULL', :delete => 'SET NULL' } ]
    else
      constraints = [ { :fk => rel.foreign_key, :table => rel.owner_class::OGTABLE, :referenced_table => rel.target_class::OGTABLE, :pk => ( rel.target_class.primary_key.field || rel.target_class.primary_key.symbol ), :update => 'SET NULL', :delete => 'SET NULL' } ]
    end
   
    constraints.each do |constraint|
      constraint[:name] = constraint_name(constraint)
    end
    
    # This checks for not-yet-enchanted entities, is there a better way?
    constraints.reject{|info| [info[:table], info[:referenced_table]].include?(:OGTABLE) }
  end


  # Returns a hash keyed by table (as a string) with each value also
  # being a hash keyed by the constraint name (as a string) and the
  # value being a string that contains the constraint definition.
  #
  # This format matches the actual constrains returned by the
  # all_foreign_keys method added to the PGConn class.

  def all_needed_constraints
    relations = manager.managed_classes.map{|klass| klass.relations}.flatten.uniq
    need_constraints = Hash.new    
    relations.each do |relation|
      infos = constraint_info(relation)
      infos.each do |info|
        # Skip constraints we already know we need
        next if need_constraints[info[:table]] and need_constraints[info[:table]].has_key? info[:name]
        need_constraints[info[:table]] ||= Hash.new
        need_constraints[info[:table]][info[:name]] = constraint_definition(info)
      end
    end
    need_constraints    
  end

  # Returns an SQL fragment containing the correct definition for a foreign key constraint.
  
  def constraint_definition(info)
    "FOREIGN KEY (#{info[:fk]}) REFERENCES #{info[:referenced_table]}(#{info[:pk]}) ON UPDATE #{info[:update]} ON DELETE #{info[:delete]}"
  end
  
  # Works the same as all_needed_constraints but only acts on one class and
  # returns the same hash as part of yet another hash with two keys, tables
  # and constraints. This is done to prevent having to resolve the
  # relations again later just to map tables.
  
  def needed_constraints(klass)
    need_constraints = Hash.new
    tables = Array.new
    (klass.relations + klass.resolve_remote_relations).each do |rel|
      constraint_info(rel).each do |info|
        tables.concat [info[:table], info[:referenced_table]]
        need_constraints[info[:table]] ||= Hash.new
        need_constraints[info[:table]][info[:name]] = constraint_definition(info)
      end
    end  
    { :tables => tables.uniq, :constraints => need_constraints }
  end
  
  # Returns the appropriate constraint prefix for a foreign key constraint.
  
  def constraint_prefix
    "#{Og.table_prefix}c"
  end
  
  # Returns the appropriate name for a constraint element generated by
  # the constraint_info method.  
   
  def constraint_name(hash)
    "#{constraint_prefix}_#{hash[:table]}_#{hash[:fk]}"
  end
  
  def needed_constraints_sql(klass = nil)
    if klass
      constraints = needed_constraints(klass)
      all_needed = constraints[:constraints]
      all_existing = Hash.new
      constraints[:tables].each do |table|
        all_existing[table] = @conn.table_foreign_keys(table)
      end
    else
      all_existing = @conn.all_foreign_keys
      all_needed = all_needed_constraints
    end
         
    drop_constraints = Array.new
    create_constraints = Array.new
      
    all_needed.each_pair do |table,constraints|
      constraints.each_pair do |name,definition|
      
        # If neither of these are matched, the constraint already exists
        # and has the correct definition.
        
        if all_existing[table].nil? or all_existing[table][name].nil?
        
          # Does not exist in database
          
          create_constraints << "ALTER TABLE #{table} ADD CONSTRAINT #{name} #{definition}"
        elsif all_existing[table][name] != definition
        
          # Exists in database and matches the object structure but has the
          # wrong definition (unlikely to happen very often).
          
          Logger.debug "PostgreSQL database contains a constraint on table '#{table}' named '#{name}' which is incorrectly defined and will be redefined (OLD: '#{all_existing[table][name]}', NEW: '#{definition}')" if $DBG
          drop_constraints << "ALTER TABLE #{table} DROP CONSTRAINT #{name}"
          create_constraints << "ALTER TABLE #{table} ADD CONSTRAINT #{name} #{definition}"
        end
      end
    end

    # You can't do this when managing classes seperately without spidering
    # each other class managed by this stores manager as other classes
    # can want relations within the same tables too. I will add spidering
    # support at some point but this isn't very important since these
    # complicated and convoluted routines will now rarely happen thank
    # to the setup hooking.

    unless klass
      all_existing.each_pair do |table,constraints|
        constraints.each_key do |name|
          if all_needed[table].nil? or all_needed[table][name].nil?
            
            # Exists in database but doesn't match object model at all
            raise Exception if table.to_s.downcase == "table"
            Logger.debug "PostgreSQL database contains a constraint on table '#{table}' named '#{name}' which does not match the object model and will be deleted" if $DBG
            drop_constraints << "ALTER TABLE #{table} DROP CONSTRAINT #{name}"
          end
        end
      end
    end
      
    {
      :drop => drop_constraints,
      :create => create_constraints
    }
      
  end
  
  # Takes a hash with constraints to drop and create and performs
  # the work.
  
  def create_constraints(param = nil)
    subsection_only = !!param
    sql_hash = param ? param : needed_constraints_sql
    Logger.debug "PostgreSQL processing foreign key constraints" unless subsection_only if $DBG
    started = Time.now
    deleted = 0
    nulled_relations = 0
    deleted_relations = 0
    created = 0
  
    sql_hash[:drop].each do |sql|
      begin
        @conn.exec(sql)
      rescue RuntimeError => ex
        raise unless ex.message =~ /does not exist/
      end
      deleted += 1
    end

    nullified_relations = 0
    sql_hash[:create].each do |sql|    
      con_retry = true
      begin
        @conn.exec(sql)
        created += 1
      rescue PGError,RuntimeError => ex
        next if ex.message =~ /already exists/ # Racing
        unless ex.message =~ /.*violates foreign key constraint.*/
          Logger.error "PostgreSQL connection returned an error for query #{sql}"
          raise
        end
        if @options[:evolve_schema] == true and @options[:evolve_schema_cautious] == false
          table, name, fk, referenced_table, pk =  sql.match(/^ALTER TABLE (\S+) ADD CONSTRAINT (\S+) FOREIGN KEY \((\S+)\) REFERENCES ([^ (]+)[ (]+([^)]+)/).captures
          raise if [table,fk,pk,referenced_table].include? nil

          cleaner_sql = "UPDATE #{table} SET #{fk} = NULL WHERE #{fk} NOT IN (SELECT #{pk} FROM #{referenced_table})"
          begin
            @conn.exec(cleaner_sql)
            if cleaner_sql[0..5] == "UPDATE"
              nulled_relations += 1
            else
              deleted_relations += 1
            end
              
          rescue PGError,RuntimeError => ex
            if ex.message =~ /.*violates not-null constraint.*/
              cleaner_sql = "DELETE FROM #{table} WHERE #{fk} NOT IN (SELECT #{pk} FROM #{referenced_table})"
              retry
            end
            Logger.error "PostgreSQL connection returned an error for query '#{cleaner_sql}' which was attempting to tidy up ready for the query '#{sql}'"
            raise
          end
            
          Logger.error "There were relationships in table #{table} that did not exist so they have been set to NULL (or deleted if this was not possible, i.e. for a join table)."
          if con_retry
            con_retry = false
            retry
          end
        else
          Logger.error "There are relationships in table #{table} that do not exist. Your database is corrupt. Please fix these or enable evolve_schema not in cautious mode and they will be fixed automatically."
        end
      end    
    end
    finished = Time.now
    taken = Kernel.sprintf("%.2f", finished - started)
    broken_relations = nulled_relations + deleted_relations
    text = "PostgreSQL finished setting constraints. "
    need_comma = false
    if [0,0,0] == [deleted,created,broken_relations]
      return if subsection_only # Make less chatty for short calls
      text << "No action was taken, "
    else
      text << "#{created} constraints were added, " if created != 0
      text << "#{deleted} constraints were deleted, " if deleted != 0
      if broken_relations != 0
        text.gsub!(/,([^,]+)$/,' and \1')
        text << "#{broken_relations} relations were broken causing "
        if nullified_relations != 0
          text << "#{nullified_relations} relations to have non-existant foreign keys set to null"
          text << (deleted_relations == 0 ? ", " : " and ")
        end
        text << "#{nullified_relations} relations to have rows with non-existant foreign keys deleted, " if deleted_relations != 0
      end
    end
    text = text[0..-3].gsub(/,([^,]+)$/,' and \1')
    text << " in #{taken} seconds."
    Logger.debug text if $DBG
  end
  
  # Called by Og.manager (in turn called by Og.setup) when Og.setup
  # has finished, allowing better processing of foreign key
  # constraints and possibly other enhancements.
  
  def post_setup
    create_constraints
  end
  
private

  def create_table(klass)
    fields = fields_for_class(klass)

    unless @conn.table_exists? klass::OGTABLE

      sql = "CREATE TABLE #{klass::OGTABLE} (#{fields.join(', ')}"

      # Create table constraints.

      if constraints = klass.ann.self[:sql_constraint]
        sql << ", #{constraints.join(', ')}"
      end

      sql << ") WITHOUT OIDS;"

      # Create indices.

      if indices = klass.ann.self[:index]
        for data in indices
          idx, options = *data
          idx = idx.to_s
          pre_sql, post_sql = options[:pre], options[:post]
          idxname = idx.gsub(/ /, "").gsub(/,/, "_").gsub(/\(.*\)/, "")
          sql << " CREATE #{pre_sql} INDEX #{klass::OGTABLE}_#{idxname}_idx #{post_sql} ON #{klass::OGTABLE} (#{idx});"  
        end
      end
        begin
          res = @conn.exec(sql)
          res.clear
          Logger.info "Created table '#{klass::OGTABLE}'."
        rescue RuntimeError => ex
          catch :ok do # Racing        
            throw :ok if ex.message =~ /duplicate key violates unique constraint "pg_class_relname_nsp_index"/
            throw :ok if ex.message =~ /already exists/
            raise
          end          
        end
    else
      Logger.debug "Table #{klass::OGTABLE} already exists" if $DBG
      #rp: basic field interrogation
      # TODO: Add type checking.

      actual_fields = @conn.table_field_list(klass::OGTABLE).map {|pair| pair.first}

      #Make new ones always - don't destroy by default because it might contain data you want back.
      need_fields = fields.each do |needed_field|
        field_name = needed_field[0..(needed_field.index(' ')-1)]
        next if actual_fields.include?(field_name)

        if @options[:evolve_schema] == true
          Logger.debug "Adding field '#{needed_field}' to '#{klass::OGTABLE}'" if $DBG
          sql = "ALTER TABLE #{klass::OGTABLE} ADD COLUMN #{needed_field}"
          begin
            @conn.exec(sql)
          rescue RuntimeError => ex
            raise unless ex.message =~ /already exists/
          end
        else
          Logger.info "WARNING: Table '#{klass::OGTABLE}' is missing field '#{needed_field}' and :evolve_schema is not set to true!"
        end
      end

      #Drop old ones
      needed_fields = fields.map {|f| f =~ /^([^ ]+)/; $1}
      actual_fields.each do |obsolete_field|
        next if needed_fields.include?(obsolete_field)
        if @options[:evolve_schema] == true and @options[:evolve_schema_cautious] == false
          sql = "ALTER TABLE #{klass::OGTABLE} DROP COLUMN #{obsolete_field}"
          begin
            @conn.exec(sql)
          rescue RuntimeError => ex
            raise unless ex.message =~ /does not exist/
            Logger.debug "Removed obsolete field '#{obsolete_field}' from '#{klass::OGTABLE}'" if $DBG
          end
       else
          Logger.info "WARNING: You have an obsolete field '#{obsolete_field}' on table '#{klass::OGTABLE}' and :evolve_schema is not set or is in cautious mode!"
        end
      end
    end

    # Create join tables if needed. Join tables are used in
    # 'many_to_many' relations.
    
    # For some reason this is missing a self join case
    # and therefore can't be used.
#    if join_tables = klass.ann.self[:join_tables]
#      for info in join_tables
#        unless @conn.table_exists? info[:table]
#      join_tables = Array.new
#      join_tables = klass.relations.reject{|rel| !rel.join_table}.map{|rel| join_table_info(rel)}
    if join_tables = klass.ann.self[:join_tables]
      for info in join_tables
        unless @conn.table_exists? info[:table]
          create_join_table_sql(info).each do |sql|
            begin
              res = @conn.exec(sql)
              res.clear
            rescue RuntimeError => ex
              raise unless ex.message =~ /duplicate key violates unique constraint "pg_class_relname_nsp_index"/
              # Racing
            end
          end
          Logger.debug "Created jointable '#{info[:table]}'." if $DBG
        else
          Logger.debug "Join table '#{info[:table]}' already exists." if $DBG
        end
      end
    end

    # If we are being called by Og.setup, we can use a much cleaner method
    # for constructing foreign key constraints.
    return if @options[:called_by_og_setup]
    
    # Strip out old constraints... this shouldn't always be necessary but
    # must be here for now while glycerin is still bleeding-edge to fix
    # changes and a nasty error that made it into the glycerin developers
    # darcs repo (but NOT into any released version of Nitro)

    unless @options[:leave_constraints] == true or @stripped_constraints
      Logger.debug "Stripping PostgreSQL foreign key constraints" if $DBG
      all_foreign_keys.map{|k| k[1].map{|v| [k[0],v[0]] }[0]}.each do |table,constraint|
          prefix = constraint_prefix
          next unless constraint[0-prefix.size..-1] == constraint_prefix
          begin
            m.store.conn.exec "ALTER TABLE #{table} DROP CONSTRAINT #{constraint}"
          rescue Exception
          end
      end
    end
    
    # Create sql constraints
    create_constraints(needed_constraints_sql(klass))

  end

  def drop_table(klass)
    # foreign key constraints will remove the need to do manual cleanup on
    # related rows.
    exec "DROP TABLE #{klass.table} CASCADE"
  end
  
  def create_field_map(klass)
    begin
      res = @conn.exec "SELECT * FROM #{klass::OGTABLE} LIMIT 1"
    rescue RuntimeError => ex
      raise unless ex.message =~ /does not exist/ or ex.message =~ /deleted while still in use/
      # Racing
      create_table(klass)
      retry
    end
    map = {}

    # Check if the field should be ignored.
    ignore = klass.ann[:self][:ignore_field] || klass.ann[:self][:ignore_fields] || klass.ann[:self][:ignore_columns]   

    for field in res.fields
      field_name = field.to_sym
      
      unless (ignore and ignore.include?(field_name))
        map[field_name] = res.fieldnum(field)
      end
    end
    
    return map
  ensure
    res.clear if res
  end

  def read_prop(p, col)
    if p.klass.ancestors.include?(Integer)
      return "#{self.class}.parse_int(res.getvalue(row, #{col} + offset))"
    elsif p.klass.ancestors.include?(Float)
      return "#{self.class}.parse_float(res.getvalue(row, #{col} + offset))"
    elsif p.klass.ancestors.include?(String)
      return "res.getvalue(row, #{col} + offset)"
    elsif p.klass.ancestors.include?(Time)
      return "#{self.class}.parse_timestamp(res.getvalue(row, #{col} + offset))"
    elsif p.klass.ancestors.include?(Date)
      return "#{self.class}.parse_date(res.getvalue(row, #{col} + offset))"
    elsif p.klass.ancestors.include?(TrueClass)
      return %|('t' == res.getvalue(row, #{col} + offset))|
    elsif p.klass.ancestors.include?(Og::Blob)
      return "#{self.class}.parse_blob(res.getvalue(row, #{col} + offset))"
    else 
      return "YAML.load(res.getvalue(row, #{col} + offset))"
    end    
  end

  #--
  # TODO: create stored procedure.
  #++

  def eval_og_insert(klass)
    props = klass.properties.values.dup
    values = props.collect { |p| write_prop(p) }.join(',') 

    if klass.schema_inheritance?
      props << Property.new(:symbol => :ogtype, :klass => String)
      values << ", '#{klass}'"
    end

    sql = "INSERT INTO #{klass::OGTABLE} (#{props.collect {|p| field_for_property(p)}.join(',')}) VALUES (#{values})"

    klass.class_eval %{ 
      def og_insert(store)
        #{::Aspects.gen_advice_code(:og_insert, klass.advices, :pre) if klass.respond_to?(:advices)}
        res = store.conn.exec "SELECT nextval('#{klass::OGSEQ}')"
        @#{klass.pk_symbol} = res.getvalue(0, 0).to_i
        res.clear
        store.conn.exec("#{sql}").clear
        #{::Aspects.gen_advice_code(:og_insert, klass.advices, :post) if klass.respond_to?(:advices)}
      end
    }
  end

  def eval_og_allocate(klass)  
    if klass.schema_inheritance?
      klass.module_eval %{
        def self.og_allocate(res, row = 0)
          Object.constant(res.getvalue(row, 0)).allocate
        end
      }
    else
      klass.module_eval %{
        def self.og_allocate(res, row = 0)
          self.allocate
        end
      }
    end
  end

  def read_row(obj, res, res_row, row)
    res.fields.each_with_index do |field, idx|
      obj.instance_variable_set "@#{field}", res.getvalue(row, idx)
    end
  end

end

end

# * George Moschovitis <gm@navel.gr>
# * Rob Pitt <rob@motionpath.com>
# * Michael Neumann <mneumann@ntecs.de>
# * Ysabel <deb@ysabel.org>