Source code for fireant.database.postgresql

from pypika import (
    PostgreSQLQuery,
    Table,
    functions as fn,
    terms,
)

from .base import Database


class DateTrunc(terms.Function):
    """
    Wrapper for the PostgreSQL date_trunc function
    """

    def __init__(self, field, date_format, alias=None):
        super(DateTrunc, self).__init__('DATE_TRUNC', date_format, field, alias=alias)
        # Setting the fields here means we can access the TRUNC args by name.
        self.field = field
        self.date_format = date_format
        self.alias = alias


class PostgreSQLDatabase(Database):
    """
    PostgreSQL client that uses the psycopg module.
    """

    # The pypika query class to use for constructing queries
    query_cls = PostgreSQLQuery

    def __init__(self, host='localhost', port=5432, database=None,
                 user=None, password=None, **kwags):
        super(PostgreSQLDatabase, self).__init__(host, port, database, **kwags)
        self.user = user
        self.password = password

    def connect(self):
        import psycopg2

        return psycopg2.connect(host=self.host, port=self.port, dbname=self.database,
                                user=self.user, password=self.password)

    def trunc_date(self, field, interval):
        return DateTrunc(field, str(interval))

    def date_add(self, field, date_part, interval):
        return fn.DateAdd(str(date_part), interval, field)

    def get_column_definitions(self, schema, table):
        """ Return a list of column name, column data type pairs """
        columns = Table('columns', schema='INFORMATION_SCHEMA')

        columns_query = PostgreSQLQuery.from_(columns) \
            .select(columns.column_name, columns.data_type) \
            .where(columns.table_schema == schema) \
            .where(columns.field('table_name') == table) \
            .distinct() \
            .orderby(columns.column_name)

        return self.fetch(str(columns_query))