Merge pull request #7447 from etehtsea/postgresql-adapter

Modularize postgresql adapter

activerecord/lib/active_record/connection_adapters/postgresql/cast.rb

+module ActiveRecord
+  module ConnectionAdapters
+    class PostgreSQLColumn < Column
+      module Cast
+        def string_to_time(string)
+          return string unless String === string
+
+          case string
+          when 'infinity'; 1.0 / 0.0
+          when '-infinity'; -1.0 / 0.0
+          else
+            super
+          end
+        end
+
+        def hstore_to_string(object)
+          if Hash === object
+            object.map { |k,v|
+              "#{escape_hstore(k)}=>#{escape_hstore(v)}"
+            }.join ','
+          else
+            object
+          end
+        end
+
+        def string_to_hstore(string)
+          if string.nil?
+            nil
+          elsif String === string
+            Hash[string.scan(HstorePair).map { |k,v|
+              v = v.upcase == 'NULL' ? nil : v.gsub(/^"(.*)"$/,'\1').gsub(/\\(.)/, '\1')
+              k = k.gsub(/^"(.*)"$/,'\1').gsub(/\\(.)/, '\1')
+              [k,v]
+            }]
+          else
+            string
+          end
+        end
+
+        def string_to_cidr(string)
+          if string.nil?
+            nil
+          elsif String === string
+            IPAddr.new(string)
+          else
+            string
+          end
+        end
+
+        def cidr_to_string(object)
+          if IPAddr === object
+            "#{object.to_s}/#{object.instance_variable_get(:@mask_addr).to_s(2).count('1')}"
+          else
+            object
+          end
+        end
+
+        private
+
+          HstorePair = begin
+            quoted_string = /"[^"\\]*(?:\\.[^"\\]*)*"/
+            unquoted_string = /(?:\\.|[^\s,])[^\s=,\\]*(?:\\.[^\s=,\\]*|=[^,>])*/
+            /(#{quoted_string}|#{unquoted_string})\s*=>\s*(#{quoted_string}|#{unquoted_string})/
+          end
+
+          def escape_hstore(value)
+            if value.nil?
+              'NULL'
+            else
+              if value == ""
+                '""'
+              else
+                '"%s"' % value.to_s.gsub(/(["\\])/, '\\\\\1')
+              end
+            end
+          end
+      end
+    end
+  end
+end

activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb

+module ActiveRecord
+  module ConnectionAdapters
+    class PostgreSQLAdapter < AbstractAdapter
+      module DatabaseStatements
+        def explain(arel, binds = [])
+          sql = "EXPLAIN #{to_sql(arel, binds)}"
+          ExplainPrettyPrinter.new.pp(exec_query(sql, 'EXPLAIN', binds))
+        end
+
+        class ExplainPrettyPrinter # :nodoc:
+          # Pretty prints the result of a EXPLAIN in a way that resembles the output of the
+          # PostgreSQL shell:
+          #
+          #                                     QUERY PLAN
+          #   ------------------------------------------------------------------------------
+          #    Nested Loop Left Join  (cost=0.00..37.24 rows=8 width=0)
+          #      Join Filter: (posts.user_id = users.id)
+          #      ->  Index Scan using users_pkey on users  (cost=0.00..8.27 rows=1 width=4)
+          #            Index Cond: (id = 1)
+          #      ->  Seq Scan on posts  (cost=0.00..28.88 rows=8 width=4)
+          #            Filter: (posts.user_id = 1)
+          #   (6 rows)
+          #
+          def pp(result)
+            header = result.columns.first
+            lines  = result.rows.map(&:first)
+
+            # We add 2 because there's one char of padding at both sides, note
+            # the extra hyphens in the example above.
+            width = [header, *lines].map(&:length).max + 2
+
+            pp = []
+
+            pp << header.center(width).rstrip
+            pp << '-' * width
+
+            pp += lines.map {|line| " #{line}"}
+
+            nrows = result.rows.length
+            rows_label = nrows == 1 ? 'row' : 'rows'
+            pp << "(#{nrows} #{rows_label})"
+
+            pp.join("\n") + "\n"
+          end
+        end
+
+        # Executes a SELECT query and returns an array of rows. Each row is an
+        # array of field values.
+        def select_rows(sql, name = nil)
+          select_raw(sql, name).last
+        end
+
+        # Executes an INSERT query and returns the new record's ID
+        def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
+          unless pk
+            # Extract the table from the insert sql. Yuck.
+            table_ref = extract_table_ref_from_insert_sql(sql)
+            pk = primary_key(table_ref) if table_ref
+          end
+
+          if pk && use_insert_returning?
+            select_value("#{sql} RETURNING #{quote_column_name(pk)}")
+          elsif pk
+            super
+            last_insert_id_value(sequence_name || default_sequence_name(table_ref, pk))
+          else
+            super
+          end
+        end
+
+        def create
+          super.insert
+        end
+
+        # create a 2D array representing the result set
+        def result_as_array(res) #:nodoc:
+          # check if we have any binary column and if they need escaping
+          ftypes = Array.new(res.nfields) do |i|
+            [i, res.ftype(i)]
+          end
+
+          rows = res.values
+          return rows unless ftypes.any? { |_, x|
+            x == BYTEA_COLUMN_TYPE_OID || x == MONEY_COLUMN_TYPE_OID
+          }
+
+          typehash = ftypes.group_by { |_, type| type }
+          binaries = typehash[BYTEA_COLUMN_TYPE_OID] || []
+          monies   = typehash[MONEY_COLUMN_TYPE_OID] || []
+
+          rows.each do |row|
+            # unescape string passed BYTEA field (OID == 17)
+            binaries.each do |index, _|
+              row[index] = unescape_bytea(row[index])
+            end
+
+            # If this is a money type column and there are any currency symbols,
+            # then strip them off. Indeed it would be prettier to do this in
+            # PostgreSQLColumn.string_to_decimal but would break form input
+            # fields that call value_before_type_cast.
+            monies.each do |index, _|
+              data = row[index]
+              # Because money output is formatted according to the locale, there are two
+              # cases to consider (note the decimal separators):
+              #  (1) $12,345,678.12
+              #  (2) $12.345.678,12
+              case data
+              when /^-?\D+[\d,]+\.\d{2}$/  # (1)
+                data.gsub!(/[^-\d.]/, '')
+              when /^-?\D+[\d.]+,\d{2}$/  # (2)
+                data.gsub!(/[^-\d,]/, '').sub!(/,/, '.')
+              end
+            end
+          end
+        end
+
+        # Queries the database and returns the results in an Array-like object
+        def query(sql, name = nil) #:nodoc:
+          log(sql, name) do
+            result_as_array @connection.async_exec(sql)
+          end
+        end
+
+        # Executes an SQL statement, returning a PGresult object on success
+        # or raising a PGError exception otherwise.
+        def execute(sql, name = nil)
+          log(sql, name) do
+            @connection.async_exec(sql)
+          end
+        end
+
+        def substitute_at(column, index)
+          Arel::Nodes::BindParam.new "$#{index + 1}"
+        end
+
+        def exec_query(sql, name = 'SQL', binds = [])
+          log(sql, name, binds) do
+            result = binds.empty? ? exec_no_cache(sql, binds) :
+                                    exec_cache(sql, binds)
+
+            types = {}
+            result.fields.each_with_index do |fname, i|
+              ftype = result.ftype i
+              fmod  = result.fmod i
+              types[fname] = OID::TYPE_MAP.fetch(ftype, fmod) { |oid, mod|
+                warn "unknown OID: #{fname}(#{oid}) (#{sql})"
+                OID::Identity.new
+              }
+            end
+
+            ret = ActiveRecord::Result.new(result.fields, result.values, types)
+            result.clear
+            return ret
+          end
+        end
+
+        def exec_delete(sql, name = 'SQL', binds = [])
+          log(sql, name, binds) do
+            result = binds.empty? ? exec_no_cache(sql, binds) :
+                                    exec_cache(sql, binds)
+            affected = result.cmd_tuples
+            result.clear
+            affected
+          end
+        end
+        alias :exec_update :exec_delete
+
+        def sql_for_insert(sql, pk, id_value, sequence_name, binds)
+          unless pk
+            # Extract the table from the insert sql. Yuck.
+            table_ref = extract_table_ref_from_insert_sql(sql)
+            pk = primary_key(table_ref) if table_ref
+          end
+
+          if pk && use_insert_returning?
+            sql = "#{sql} RETURNING #{quote_column_name(pk)}"
+          end
+
+          [sql, binds]
+        end
+
+        def exec_insert(sql, name, binds, pk = nil, sequence_name = nil)
+          val = exec_query(sql, name, binds)
+          if !use_insert_returning? && pk
+            unless sequence_name
+              table_ref = extract_table_ref_from_insert_sql(sql)
+              sequence_name = default_sequence_name(table_ref, pk)
+              return val unless sequence_name
+            end
+            last_insert_id_result(sequence_name)
+          else
+            val
+          end
+        end
+
+        # Executes an UPDATE query and returns the number of affected tuples.
+        def update_sql(sql, name = nil)
+          super.cmd_tuples
+        end
+
+        # Begins a transaction.
+        def begin_db_transaction
+          execute "BEGIN"
+        end
+
+        # Commits a transaction.
+        def commit_db_transaction
+          execute "COMMIT"
+        end
+
+        # Aborts a transaction.
+        def rollback_db_transaction
+          execute "ROLLBACK"
+        end
+
+        def outside_transaction?
+          @connection.transaction_status == PGconn::PQTRANS_IDLE
+        end
+
+        def create_savepoint
+          execute("SAVEPOINT #{current_savepoint_name}")
+        end
+
+        def rollback_to_savepoint
+          execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}")
+        end
+
+        def release_savepoint
+          execute("RELEASE SAVEPOINT #{current_savepoint_name}")
+        end
+      end
+    end
+  end
+end

activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb

+module ActiveRecord
+  module ConnectionAdapters
+    class PostgreSQLAdapter < AbstractAdapter
+      module Quoting
+        # Escapes binary strings for bytea input to the database.
+        def escape_bytea(value)
+          PGconn.escape_bytea(value) if value
+        end
+
+        # Unescapes bytea output from a database to the binary string it represents.
+        # NOTE: This is NOT an inverse of escape_bytea! This is only to be used
+        #       on escaped binary output from database drive.
+        def unescape_bytea(value)
+          PGconn.unescape_bytea(value) if value
+        end
+
+        # Quotes PostgreSQL-specific data types for SQL input.
+        def quote(value, column = nil) #:nodoc:
+          return super unless column
+
+          case value
+          when Hash
+            case column.sql_type
+            when 'hstore' then super(PostgreSQLColumn.hstore_to_string(value), column)
+            else super
+            end
+          when IPAddr
+            case column.sql_type
+            when 'inet', 'cidr' then super(PostgreSQLColumn.cidr_to_string(value), column)
+            else super
+            end
+          when Float
+            if value.infinite? && column.type == :datetime
+              "'#{value.to_s.downcase}'"
+            elsif value.infinite? || value.nan?
+              "'#{value.to_s}'"
+            else
+              super
+            end
+          when Numeric
+            return super unless column.sql_type == 'money'
+            # Not truly string input, so doesn't require (or allow) escape string syntax.
+            "'#{value}'"
+          when String
+            case column.sql_type
+            when 'bytea' then "'#{escape_bytea(value)}'"
+            when 'xml'   then "xml '#{quote_string(value)}'"
+            when /^bit/
+              case value
+              when /^[01]*$/      then "B'#{value}'" # Bit-string notation
+              when /^[0-9A-F]*$/i then "X'#{value}'" # Hexadecimal notation
+              end
+            else
+              super
+            end
+          else
+            super
+          end
+        end
+
+        def type_cast(value, column)
+          return super unless column
+
+          case value
+          when String
+            return super unless 'bytea' == column.sql_type
+            { :value => value, :format => 1 }
+          when Hash
+            return super unless 'hstore' == column.sql_type
+            PostgreSQLColumn.hstore_to_string(value)
+          when IPAddr
+            return super unless ['inet','cidr'].includes? column.sql_type
+            PostgreSQLColumn.cidr_to_string(value)
+          else
+            super
+          end
+        end
+
+        # Quotes strings for use in SQL input.
+        def quote_string(s) #:nodoc:
+          @connection.escape(s)
+        end
+
+        # Checks the following cases:
+        #
+        # - table_name
+        # - "table.name"
+        # - schema_name.table_name
+        # - schema_name."table.name"
+        # - "schema.name".table_name
+        # - "schema.name"."table.name"
+        def quote_table_name(name)
+          schema, name_part = extract_pg_identifier_from_name(name.to_s)
+
+          unless name_part
+            quote_column_name(schema)
+          else
+            table_name, name_part = extract_pg_identifier_from_name(name_part)
+            "#{quote_column_name(schema)}.#{quote_column_name(table_name)}"
+          end
+        end
+
+        # Quotes column names for use in SQL queries.
+        def quote_column_name(name) #:nodoc:
+          PGconn.quote_ident(name.to_s)
+        end
+
+        # Quote date/time values for use in SQL input. Includes microseconds
+        # if the value is a Time responding to usec.
+        def quoted_date(value) #:nodoc:
+          if value.acts_like?(:time) && value.respond_to?(:usec)
+            "#{super}.#{sprintf("%06d", value.usec)}"
+          else
+            super
+          end
+        end
+      end
+    end
+  end
+end

activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb

+module ActiveRecord
+  module ConnectionAdapters
+    class PostgreSQLAdapter < AbstractAdapter
+      module ReferentialIntegrity
+        def supports_disable_referential_integrity? #:nodoc:
+          true
+        end
+
+        def disable_referential_integrity #:nodoc:
+          if supports_disable_referential_integrity? then
+            execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} DISABLE TRIGGER ALL" }.join(";"))
+          end
+          yield
+        ensure
+          if supports_disable_referential_integrity? then
+            execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} ENABLE TRIGGER ALL" }.join(";"))
+          end
+        end
+      end
+    end
+  end
+end

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

+module ActiveRecord
+  module ConnectionAdapters
+    class PostgreSQLAdapter < AbstractAdapter
+      module SchemaStatements
+        # Drops the database specified on the +name+ attribute
+        # and creates it again using the provided +options+.
+        def recreate_database(name, options = {}) #:nodoc:
+          drop_database(name)
+          create_database(name, options)
+        end
+
+        # Create a new PostgreSQL database. Options include <tt>:owner</tt>, <tt>:template</tt>,
+        # <tt>:encoding</tt>, <tt>:collation</tt>, <tt>:ctype</tt>,
+        # <tt>:tablespace</tt>, and <tt>:connection_limit</tt> (note that MySQL uses
+        # <tt>:charset</tt> while PostgreSQL uses <tt>:encoding</tt>).
+        #
+        # Example:
+        #   create_database config[:database], config
+        #   create_database 'foo_development', :encoding => 'unicode'
+        def create_database(name, options = {})
+          options = options.reverse_merge(:encoding => "utf8")
+
+          option_string = options.symbolize_keys.sum do |key, value|
+            case key
+            when :owner
+              " OWNER = \"#{value}\""
+            when :template
+              " TEMPLATE = \"#{value}\""
+            when :encoding
+              " ENCODING = '#{value}'"
+            when :collation
+              " LC_COLLATE = '#{value}'"
+            when :ctype
+              " LC_CTYPE = '#{value}'"
+            when :tablespace
+              " TABLESPACE = \"#{value}\""
+            when :connection_limit
+              " CONNECTION LIMIT = #{value}"
+            else
+              ""
+            end
+          end
+
+          execute "CREATE DATABASE #{quote_table_name(name)}#{option_string}"
+        end
+
+        # Drops a PostgreSQL database.
+        #
+        # Example:
+        #   drop_database 'matt_development'
+        def drop_database(name) #:nodoc:
+          execute "DROP DATABASE IF EXISTS #{quote_table_name(name)}"
+        end
+
+        # Returns the list of all tables in the schema search path or a specified schema.
+        def tables(name = nil)
+          query(<<-SQL, 'SCHEMA').map { |row| row[0] }
+            SELECT tablename
+            FROM pg_tables
+            WHERE schemaname = ANY (current_schemas(false))
+          SQL
+        end
+
+        # Returns true if table exists.
+        # If the schema is not specified as part of +name+ then it will only find tables within
+        # the current schema search path (regardless of permissions to access tables in other schemas)
+        def table_exists?(name)
+          schema, table = Utils.extract_schema_and_table(name.to_s)
+          return false unless table
+
+          binds = [[nil, table]]
+          binds << [nil, schema] if schema
+
+          exec_query(<<-SQL, 'SCHEMA').rows.first[0].to_i > 0
+              SELECT COUNT(*)
+              FROM pg_class c
+              LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
+              WHERE c.relkind in ('v','r')
+              AND c.relname = '#{table.gsub(/(^"|"$)/,'')}'
+              AND n.nspname = #{schema ? "'#{schema}'" : 'ANY (current_schemas(false))'}
+          SQL
+        end
+
+        # Returns true if schema exists.
+        def schema_exists?(name)
+          exec_query(<<-SQL, 'SCHEMA').rows.first[0].to_i > 0
+            SELECT COUNT(*)
+            FROM pg_namespace
+            WHERE nspname = '#{name}'
+          SQL
+        end
+
+        # Returns an array of indexes for the given table.
+        def indexes(table_name, name = nil)
+           result = query(<<-SQL, 'SCHEMA')
+             SELECT distinct i.relname, d.indisunique, d.indkey, pg_get_indexdef(d.indexrelid), t.oid
+             FROM pg_class t
+             INNER JOIN pg_index d ON t.oid = d.indrelid
+             INNER JOIN pg_class i ON d.indexrelid = i.oid
+             WHERE i.relkind = 'i'
+               AND d.indisprimary = 'f'
+               AND t.relname = '#{table_name}'
+               AND i.relnamespace IN (SELECT oid FROM pg_namespace WHERE nspname = ANY (current_schemas(false)) )
+            ORDER BY i.relname
+          SQL
+
+          result.map do |row|
+            index_name = row[0]
+            unique = row[1] == 't'
+            indkey = row[2].split(" ")
+            inddef = row[3]
+            oid = row[4]
+
+            columns = Hash[query(<<-SQL, "Columns for index #{row[0]} on #{table_name}")]
+            SELECT a.attnum, a.attname
+            FROM pg_attribute a
+            WHERE a.attrelid = #{oid}
+            AND a.attnum IN (#{indkey.join(",")})
+            SQL
+
+            column_names = columns.values_at(*indkey).compact
+
+            # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
+            desc_order_columns = inddef.scan(/(\w+) DESC/).flatten
+            orders = desc_order_columns.any? ? Hash[desc_order_columns.map {|order_column| [order_column, :desc]}] : {}
+            where = inddef.scan(/WHERE (.+)$/).flatten[0]
+
+            column_names.empty? ? nil : IndexDefinition.new(table_name, index_name, unique, column_names, [], orders, where)
+          end.compact
+        end
+
+        # Returns the list of all column definitions for a table.
+        def columns(table_name)
+          # Limit, precision, and scale are all handled by the superclass.
+          column_definitions(table_name).map do |column_name, type, default, notnull, oid, fmod|
+            oid = OID::TYPE_MAP.fetch(oid.to_i, fmod.to_i) {
+              OID::Identity.new
+            }
+            PostgreSQLColumn.new(column_name, default, oid, type, notnull == 'f')
+          end
+        end
+
+        # Returns the current database name.
+        def current_database
+          query('select current_database()', 'SCHEMA')[0][0]
+        end
+
+        # Returns the current schema name.
+        def current_schema
+          query('SELECT current_schema', 'SCHEMA')[0][0]
+        end
+
+        # Returns the current database encoding format.
+        def encoding
+          query(<<-end_sql, 'SCHEMA')[0][0]
+            SELECT pg_encoding_to_char(pg_database.encoding) FROM pg_database
+            WHERE pg_database.datname LIKE '#{current_database}'
+          end_sql
+        end
+
+        # Returns the current database collation.
+        def collation
+          query(<<-end_sql, 'SCHEMA')[0][0]
+            SELECT pg_database.datcollate FROM pg_database WHERE pg_database.datname LIKE '#{current_database}'
+          end_sql
+        end
+
+        # Returns the current database ctype.
+        def ctype
+          query(<<-end_sql, 'SCHEMA')[0][0]
+            SELECT pg_database.datctype FROM pg_database WHERE pg_database.datname LIKE '#{current_database}'
+          end_sql
+        end
+
+        # Returns an array of schema names.
+        def schema_names
+          query(<<-SQL, 'SCHEMA').flatten
+            SELECT nspname
+              FROM pg_namespace
+             WHERE nspname !~ '^pg_.*'
+               AND nspname NOT IN ('information_schema')
+             ORDER by nspname;
+          SQL
+        end
+
+        # Creates a schema for the given schema name.
+        def create_schema schema_name
+          execute "CREATE SCHEMA #{schema_name}"
+        end
+
+        # Drops the schema for the given schema name.
+        def drop_schema schema_name
+          execute "DROP SCHEMA #{schema_name} CASCADE"
+        end
+
+        # Sets the schema search path to a string of comma-separated schema names.
+        # Names beginning with $ have to be quoted (e.g. $user => '$user').
+        # See: http://www.postgresql.org/docs/current/static/ddl-schemas.html
+        #
+        # This should be not be called manually but set in database.yml.
+        def schema_search_path=(schema_csv)
+          if schema_csv
+            execute("SET search_path TO #{schema_csv}", 'SCHEMA')
+            @schema_search_path = schema_csv
+          end
+        end
+
+        # Returns the active schema search path.
+        def schema_search_path
+          @schema_search_path ||= query('SHOW search_path', 'SCHEMA')[0][0]
+        end
+
+        # Returns the current client message level.
+        def client_min_messages
+          query('SHOW client_min_messages', 'SCHEMA')[0][0]
+        end
+
+        # Set the client message level.
+        def client_min_messages=(level)
+          execute("SET client_min_messages TO '#{level}'", 'SCHEMA')
+        end
+
+        # Returns the sequence name for a table's primary key or some other specified key.
+        def default_sequence_name(table_name, pk = nil) #:nodoc:
+          result = serial_sequence(table_name, pk || 'id')
+          return nil unless result
+          result.split('.').last
+        rescue ActiveRecord::StatementInvalid
+          "#{table_name}_#{pk || 'id'}_seq"
+        end
+
+        def serial_sequence(table, column)
+          result = exec_query(<<-eosql, 'SCHEMA')
+            SELECT pg_get_serial_sequence('#{table}', '#{column}')
+          eosql
+          result.rows.first.first
+        end
+
+        # Resets the sequence of a table's primary key to the maximum value.
+        def reset_pk_sequence!(table, pk = nil, sequence = nil) #:nodoc:
+          unless pk and sequence
+            default_pk, default_sequence = pk_and_sequence_for(table)
+
+            pk ||= default_pk
+            sequence ||= default_sequence
+          end
+
+          if @logger && pk && !sequence
+            @logger.warn "#{table} has primary key #{pk} with no default sequence"
+          end
+
+          if pk && sequence
+            quoted_sequence = quote_table_name(sequence)
+
+            select_value <<-end_sql, 'Reset sequence'
+              SELECT setval('#{quoted_sequence}', (SELECT COALESCE(MAX(#{quote_column_name pk})+(SELECT increment_by FROM #{quoted_sequence}), (SELECT min_value FROM #{quoted_sequence})) FROM #{quote_table_name(table)}), false)
+            end_sql
+          end
+        end
+
+        # Returns a table's primary key and belonging sequence.
+        def pk_and_sequence_for(table) #:nodoc:
+          # First try looking for a sequence with a dependency on the
+          # given table's primary key.
+          result = query(<<-end_sql, 'PK and serial sequence')[0]
+            SELECT attr.attname, seq.relname
+            FROM pg_class      seq,
+                 pg_attribute  attr,
+                 pg_depend     dep,
+                 pg_namespace  name,
+                 pg_constraint cons
+            WHERE seq.oid           = dep.objid
+              AND seq.relkind       = 'S'
+              AND attr.attrelid     = dep.refobjid
+              AND attr.attnum       = dep.refobjsubid
+              AND attr.attrelid     = cons.conrelid
+              AND attr.attnum       = cons.conkey[1]
+              AND cons.contype      = 'p'
+              AND dep.refobjid      = '#{quote_table_name(table)}'::regclass
+          end_sql
+
+          if result.nil? or result.empty?
+            # If that fails, try parsing the primary key's default value.
+            # Support the 7.x and 8.0 nextval('foo'::text) as well as
+            # the 8.1+ nextval('foo'::regclass).
+            result = query(<<-end_sql, 'PK and custom sequence')[0]
+              SELECT attr.attname,
+                CASE
+                  WHEN split_part(def.adsrc, '''', 2) ~ '.' THEN
+                    substr(split_part(def.adsrc, '''', 2),
+                           strpos(split_part(def.adsrc, '''', 2), '.')+1)
+                  ELSE split_part(def.adsrc, '''', 2)
+                END
+              FROM pg_class       t
+              JOIN pg_attribute   attr ON (t.oid = attrelid)
+              JOIN pg_attrdef     def  ON (adrelid = attrelid AND adnum = attnum)
+              JOIN pg_constraint  cons ON (conrelid = adrelid AND adnum = conkey[1])
+              WHERE t.oid = '#{quote_table_name(table)}'::regclass
+                AND cons.contype = 'p'
+                AND def.adsrc ~* 'nextval'
+            end_sql
+          end
+
+          [result.first, result.last]
+        rescue
+          nil
+        end
+
+        # Returns just a table's primary key
+        def primary_key(table)
+          row = exec_query(<<-end_sql, 'SCHEMA').rows.first
+            SELECT DISTINCT(attr.attname)
+            FROM pg_attribute attr
+            INNER JOIN pg_depend dep ON attr.attrelid = dep.refobjid AND attr.attnum = dep.refobjsubid
+            INNER JOIN pg_constraint cons ON attr.attrelid = cons.conrelid AND attr.attnum = cons.conkey[1]
+            WHERE cons.contype = 'p'
+              AND dep.refobjid = '#{table}'::regclass
+          end_sql
+
+          row && row.first
+        end
+
+        # Renames a table.
+        # Also renames a table's primary key sequence if the sequence name matches the
+        # Active Record default.
+        #
+        # Example:
+        #   rename_table('octopuses', 'octopi')
+        def rename_table(name, new_name)
+          clear_cache!
+          execute "ALTER TABLE #{quote_table_name(name)} RENAME TO #{quote_table_name(new_name)}"
+          pk, seq = pk_and_sequence_for(new_name)
+          if seq == "#{name}_#{pk}_seq"
+            new_seq = "#{new_name}_#{pk}_seq"
+            execute "ALTER TABLE #{quote_table_name(seq)} RENAME TO #{quote_table_name(new_seq)}"
+          end
+        end
+
+        # Adds a new column to the named table.
+        # See TableDefinition#column for details of the options you can use.
+        def add_column(table_name, column_name, type, options = {})
+          clear_cache!
+          add_column_sql = "ALTER TABLE #{quote_table_name(table_name)} ADD COLUMN #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
+          add_column_options!(add_column_sql, options)
+
+          execute add_column_sql
+        end
+
+        # Changes the column of a table.
+        def change_column(table_name, column_name, type, options = {})
+          clear_cache!
+          quoted_table_name = quote_table_name(table_name)
+
+          execute "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
+
+          change_column_default(table_name, column_name, options[:default]) if options_include_default?(options)
+          change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
+        end
+
+        # Changes the default value of a table column.
+        def change_column_default(table_name, column_name, default)
+          clear_cache!
+          execute "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} SET DEFAULT #{quote(default)}"
+        end
+
+        def change_column_null(table_name, column_name, null, default = nil)
+          clear_cache!
+          unless null || default.nil?
+            execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
+          end
+          execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
+        end
+
+        # Renames a column in a table.
+        def rename_column(table_name, column_name, new_column_name)
+          clear_cache!
+          execute "ALTER TABLE #{quote_table_name(table_name)} RENAME COLUMN #{quote_column_name(column_name)} TO #{quote_column_name(new_column_name)}"
+        end
+
+        def remove_index!(table_name, index_name) #:nodoc:
+          execute "DROP INDEX #{quote_table_name(index_name)}"
+        end
+
+        def rename_index(table_name, old_name, new_name)
+          execute "ALTER INDEX #{quote_column_name(old_name)} RENAME TO #{quote_table_name(new_name)}"
+        end
+
+        def index_name_length
+          63
+        end
+
+        # Maps logical Rails types to PostgreSQL-specific data types.
+        def type_to_sql(type, limit = nil, precision = nil, scale = nil)
+          case type.to_s
+          when 'binary'
+            # PostgreSQL doesn't support limits on binary (bytea) columns.
+            # The hard limit is 1Gb, because of a 32-bit size field, and TOAST.
+            case limit
+            when nil, 0..0x3fffffff; super(type)
+            else raise(ActiveRecordError, "No binary type has byte size #{limit}.")
+            end
+          when 'integer'
+            return 'integer' unless limit
+
+            case limit
+              when 1, 2; 'smallint'
+              when 3, 4; 'integer'
+              when 5..8; 'bigint'
+              else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
+            end
+          when 'datetime'
+            return super unless precision
+
+            case precision
+              when 0..6; "timestamp(#{precision})"
+              else raise(ActiveRecordError, "No timestamp type has precision of #{precision}. The allowed range of precision is from 0 to 6")
+            end
+          else
+            super
+          end
+        end
+
+        # Returns a SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause.
+        #
+        # PostgreSQL requires the ORDER BY columns in the select list for distinct queries, and
+        # requires that the ORDER BY include the distinct column.
+        #
+        #   distinct("posts.id", "posts.created_at desc")
+        def distinct(columns, orders) #:nodoc:
+          return "DISTINCT #{columns}" if orders.empty?
+
+          # Construct a clean list of column names from the ORDER BY clause, removing
+          # any ASC/DESC modifiers
+          order_columns = orders.collect do |s|
+            s = s.to_sql unless s.is_a?(String)
+            s.gsub(/\s+(ASC|DESC)\s*(NULLS\s+(FIRST|LAST)\s*)?/i, '')
+          end
+          order_columns.delete_if { |c| c.blank? }
+          order_columns = order_columns.zip((0...order_columns.size).to_a).map { |s,i| "#{s} AS alias_#{i}" }
+
+          "DISTINCT #{columns}, #{order_columns * ', '}"
+        end
+      end
+    end
+  end
+end

activerecord/test/cases/adapters/postgresql/active_schema_test.rb

@@ -3,8 +3,6 @@
 class PostgresqlActiveSchemaTest < ActiveRecord::TestCase
   def setup
     ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.class_eval do
-      alias_method :real_execute, :execute
-      remove_method :execute
       def execute(sql, name = nil) sql end
     end
   end
@@ -12,7 +10,6 @@ def execute(sql, name = nil) sql end
   def teardown
     ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.class_eval do
       remove_method :execute
-      alias_method :execute, :real_execute
     end
   end