Source code for

# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
from typing import Any, Dict, List, Tuple

from prestodb.client import PrestoResult
from prestodb.dbapi import Cursor as PrestoCursor

from import BaseSQLToGCSOperator
from airflow.providers.presto.hooks.presto import PrestoHook

class _PrestoToGCSPrestoCursorAdapter:
    An adapter that adds additional feature to the Presto cursor.

    The implementation of cursor in the prestodb library is not sufficient.
    The following changes have been made:

    * The poke mechanism for row. You can look at the next row without consuming it.
    * The description attribute is available before reading the first row. Thanks to the poke mechanism.
    * the iterator interface has been implemented.

    A detailed description of the class methods is available in
    `PEP-249 <>`__.

    def __init__(self, cursor: PrestoCursor):
        self.cursor: PrestoCursor = cursor
        self.rows: List[Any] = []
        self.initialized: bool = False

    def description(self) -> List[Tuple]:
        This read-only attribute is a sequence of 7-item sequences.

        Each of these sequences contains information describing one result column:

        * ``name``
        * ``type_code``
        * ``display_size``
        * ``internal_size``
        * ``precision``
        * ``scale``
        * ``null_ok``

        The first two items (``name`` and ``type_code``) are mandatory, the other
        five are optional and are set to None if no meaningful values can be provided.
        if not self.initialized:
            # Peek for first row to load description.
        return self.cursor.description

    def rowcount(self) -> int:
        """The read-only attribute specifies the number of rows"""
        return self.cursor.rowcount

    def close(self) -> None:
        """Close the cursor now"""

    def execute(self, *args, **kwargs) -> PrestoResult:
        """Prepare and execute a database operation (query or command)."""
        self.initialized = False
        self.rows = []
        return self.cursor.execute(*args, **kwargs)

    def executemany(self, *args, **kwargs):
        Prepare a database operation (query or command) and then execute it against all parameter
        sequences or mappings found in the sequence seq_of_parameters.
        self.initialized = False
        self.rows = []
        return self.cursor.executemany(*args, **kwargs)

    def peekone(self) -> Any:
        """Return the next row without consuming it."""
        self.initialized = True
        element = self.cursor.fetchone()
        self.rows.insert(0, element)
        return element

    def fetchone(self) -> Any:
        Fetch the next row of a query result set, returning a single sequence, or
        ``None`` when no more data is available.
        if self.rows:
            return self.rows.pop(0)
        return self.cursor.fetchone()

    def fetchmany(self, size=None) -> list:
        Fetch the next set of rows of a query result, returning a sequence of sequences
        (e.g. a list of tuples). An empty sequence is returned when no more rows are available.
        if size is None:
            size = self.cursor.arraysize

        result = []
        for _ in range(size):
            row = self.fetchone()
            if row is None:

        return result

    def __next__(self) -> Any:
        Return the next row from the currently executing SQL statement using the same semantics as
        ``.fetchone()``.  A ``StopIteration`` exception is raised when the result set is exhausted.
        result = self.fetchone()
        if result is None:
            raise StopIteration()
        return result

    def __iter__(self) -> "_PrestoToGCSPrestoCursorAdapter":
        """Return self to make cursors compatible to the iteration protocol"""
        return self

[docs]class PrestoToGCSOperator(BaseSQLToGCSOperator): """Copy data from PrestoDB to Google Cloud Storage in JSON or CSV format. :param presto_conn_id: Reference to a specific Presto hook. :type presto_conn_id: str """
[docs] ui_color = "#a0e08c"
[docs] type_map = { "BOOLEAN": "BOOL", "TINYINT": "INT64", "SMALLINT": "INT64", "INTEGER": "INT64", "BIGINT": "INT64", "REAL": "FLOAT64", "DOUBLE": "FLOAT64", "DECIMAL": "NUMERIC", "VARCHAR": "STRING", "CHAR": "STRING", "VARBINARY": "BYTES", "JSON": "STRING", "DATE": "DATE", "TIME": "TIME", # BigQuery don't time with timezone native. "TIME WITH TIME ZONE": "STRING", "TIMESTAMP": "TIMESTAMP", # BigQuery supports a narrow range of time zones during import. # You should use TIMESTAMP function, if you want have TIMESTAMP type "TIMESTAMP WITH TIME ZONE": "STRING", "IPADDRESS": "STRING", "UUID": "STRING",
} def __init__(self, *, presto_conn_id: str = "presto_default", **kwargs): super().__init__(**kwargs) self.presto_conn_id = presto_conn_id
[docs] def query(self): """Queries presto and returns a cursor to the results.""" presto = PrestoHook(presto_conn_id=self.presto_conn_id) conn = presto.get_conn() cursor = conn.cursor()"Executing: %s", self.sql) cursor.execute(self.sql) return _PrestoToGCSPrestoCursorAdapter(cursor)
[docs] def field_to_bigquery(self, field) -> Dict[str, str]: """Convert presto field type to BigQuery field type.""" clear_field_type = field[1].upper() # remove type argument e.g. DECIMAL(2, 10) => DECIMAL clear_field_type, _, _ = clear_field_type.partition("(") new_field_type = self.type_map.get(clear_field_type, "STRING") return {"name": field[0], "type": new_field_type}
[docs] def convert_type(self, value, schema_type): """ Do nothing. Presto uses JSON on the transport layer, so types are simple. :param value: Presto column value :type value: Any :param schema_type: BigQuery data type :type schema_type: str """ return value

Was this entry helpful?