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# -*- coding: utf-8 -*-
#
# Input classes for ETL, databases.
#
# Author: Just van den Broecke
#
from stetl.component import Config
from stetl.input import Input
from stetl.util import Util
from stetl.packet import FORMAT
from stetl.postgis import PostGIS
log = Util.get_log('dbinput')
class DbInput(Input):
"""
Input from any database (abstract base class).
"""
def __init__(self, configdict, section, produces):
Input.__init__(self, configdict, section, produces=produces)
def read(self, packet):
return packet
class SqlDbInput(DbInput):
"""
Input using a query from any SQL-based RDBMS (abstract base class).
"""
# Start attribute config meta
@Config(ptype=str, required=True, default=None)
def database_name(self):
"""
Database name
"""
pass
@Config(ptype=str, required=False, default=None)
def table(self):
"""
Table name
"""
pass
@Config(ptype=str, required=False, default=None)
def column_names(self):
"""
Column names to populate records with. If empty taken from table metadata.
"""
pass
@Config(ptype=bool, required=False, default=False)
def read_once(self):
"""
Read once? i.e. only do query once and stop
"""
pass
@Config(ptype=str, required=False, default=None)
def query(self):
"""
The query (string) to fire.
"""
pass
# End attribute config meta
def __init__(self, configdict, section, produces):
DbInput.__init__(self, configdict, section, produces=produces)
self.columns = self.column_names
self.select_all = "select * from %s" % self.table
def result_to_output(self, db_records):
"""
Convert DB-specific record iterator to single Python record (dict) or record array (list of dict).
"""
# record is Python list of Python dict (multiple records)
records = list()
# Convert list of lists to list of dict using column_names
for db_record in db_records:
records.append(dict(zip(self.columns, db_record)))
# We may have specified a single record output_format in rare cases
if self.output_format == FORMAT.record:
if len(records) > 0:
return records[0]
else:
return None
else:
return records
def do_query(self, query_str):
"""
DB-neutral query returning Python record list.
"""
# Perform DB-specific query
db_records = self.raw_query(query_str)
# Convert query result to record_array
return self.result_to_output(db_records)
def raw_query(self, query_str):
"""
Performs DB-specific query and returns raw records iterator.
"""
pass
def read(self, packet):
# Perform DB-specific query
packet.data = self.do_query(self.query)
# No more records to process?
if len(packet.data) == 0 or self.read_once is True:
packet.set_end_of_stream()
log.info('Nothing to do. All file_records done')
return packet
return packet
class PostgresDbInput(SqlDbInput):
"""
Input by querying records from a Postgres database.
Input is a query, like SELECT * from mytable.
Output is zero or more records as record array (array of dict) or single record (dict).
produces=FORMAT.record_array (default) or FORMAT.record
"""
# Start attribute config meta
@Config(ptype=str, required=False, default='localhost')
def host(self):
"""
host name or host IP-address, defaults to 'localhost'
"""
pass
@Config(ptype=str, required=False, default='5432')
def port(self):
"""
port for host, defaults to `'5432'
"""
pass
@Config(ptype=str, required=False, default='postgres')
def user(self):
"""
User name, defaults to 'postgres'
"""
pass
@Config(ptype=str, required=False, default='postgres')
def password(self):
"""
User password, defaults to 'postgres'
"""
pass
@Config(ptype=str, required=False, default='public')
def schema(self):
"""
The postgres schema name, defaults to 'public'
"""
pass
# End attribute config meta
def __init__(self, configdict, section):
SqlDbInput.__init__(self, configdict, section, produces=[FORMAT.record_array, FORMAT.record])
self.db = None
def init(self):
# Connect only once to DB
log.info('Init: connect to DB')
self.db = PostGIS(self.cfg.get_dict())
self.db.connect()
# If no explicit column names given, get from DB meta info
self.columns = self.column_names
if self.column_names is None:
self.columns = self.db.get_column_names(self.cfg.get('table'), self.cfg.get('schema'))
def exit(self):
# Disconnect from DB when done
log.info('Exit: disconnect from DB')
self.db.disconnect()
def raw_query(self, query_str):
self.db.execute(query_str)
db_records = self.db.cursor.fetchall()
log.info('read recs: %d' % len(db_records))
return db_records
class SqliteDbInput(SqlDbInput):
"""
Input by querying records from a SQLite database.
Input is a query, like SELECT * from mytable.
Output is zero or more records as record array (array of dict) or single record (dict).
produces=FORMAT.record_array (default) or FORMAT.record
"""
def __init__(self, configdict, section):
SqlDbInput.__init__(self, configdict, section, produces=[FORMAT.record_array, FORMAT.record])
self.db = None
import sqlite3
self.sqlite = sqlite3
def get_conn(self):
# Database name is the filepath
log.info('Connect to SQLite DB: %s' % self.database_name)
return self.sqlite.connect(self.database_name)
def init(self):
# If no explicit column names given, get from DB meta info
if self.column_names is None:
# Connect only once to DB
conn = self.get_conn()
cursor = conn.cursor()
cursor.execute(self.select_all)
self.columns = [f[0] for f in cursor.description]
conn.close()
def raw_query(self, query_str):
# We open and close immediately. TODO: maybe this is not necessary i.e. once in init/exit.
conn = self.get_conn()
cursor = conn.cursor()
cursor.execute(query_str)
db_records = cursor.fetchall()
log.info('%d records read' % len(db_records))
conn.close()
return db_records
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