# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 108
def begin_db_transaction
  execute("BEGIN", "TRANSACTION")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 112
def begin_isolated_db_transaction(isolation)
  begin_db_transaction
  execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 118
def commit_db_transaction
  execute("COMMIT", "TRANSACTION")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 69
def exec_delete(sql, name = nil, binds = [])
  execute_and_clear(sql, name, binds) { |result| result.cmd_tuples }
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 89
def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil)
  if use_insert_returning? || pk == false
    super
  else
    result = exec_query(sql, name, binds)
    unless sequence_name
      table_ref = extract_table_ref_from_insert_sql(sql)
      if table_ref
        pk = primary_key(table_ref) if pk.nil?
        pk = suppress_composite_primary_key(pk)
        sequence_name = default_sequence_name(table_ref, pk)
      end
      return result unless sequence_name
    end
    last_insert_id_result(sequence_name)
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 52
def exec_query(sql, name = "SQL", binds = [], prepare: false)
  execute_and_clear(sql, name, binds, prepare: prepare) do |result|
    types = {}
    fields = result.fields
    fields.each_with_index do |fname, i|
      ftype = result.ftype i
      fmod  = result.fmod i
      case type = get_oid_type(ftype, fmod, fname)
      when Type::Integer, Type::Float, OID::Decimal, Type::String, Type::DateTime, Type::Boolean
        # skip if a column has already been type casted by pg decoders
      else types[fname] = type
      end
    end
    build_result(columns: fields, rows: result.values, column_types: types)
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 123
def exec_rollback_db_transaction
  execute("ROLLBACK", "TRANSACTION")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 37
def execute(sql, name = nil)
  if preventing_writes? && write_query?(sql)
    raise ActiveRecord::ReadOnlyError, "Write query attempted while in readonly mode: #{sql}"
  end

  materialize_transactions
  mark_transaction_written_if_write(sql)

  log(sql, name) do
    ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
      @connection.async_exec(sql)
    end
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 7
def explain(arel, binds = [])
  sql = "EXPLAIN #{to_sql(arel, binds)}"
  PostgreSQL::ExplainPrettyPrinter.new.pp(exec_query(sql, "EXPLAIN", binds))
end