287 lines
10 KiB
Python
287 lines
10 KiB
Python
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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""Create web2py model (python code) to represent PostgreSQL tables.
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Features:
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* Uses ANSI Standard INFORMATION_SCHEMA (might work with other RDBMS)
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* Detects legacy "keyed" tables (not having an "id" PK)
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* Connects directly to running databases, no need to do a SQL dump
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* Handles notnull, unique and referential constraints
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* Detects most common datatypes and default values
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* Support PostgreSQL columns comments (ie. for documentation)
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Requeriments:
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* Needs PostgreSQL pyscopg2 python connector (same as web2py)
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* If used against other RDBMS, import and use proper connector (remove pg_ code)
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Created by Mariano Reingart, based on a script to "generate schemas from dbs"
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(mysql) by Alexandre Andrade
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"""
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_author__ = "Mariano Reingart <reingart@gmail.com>"
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HELP = """
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USAGE: extract_pgsql_models db host port user passwd
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Call with PostgreSQL database connection parameters,
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web2py model will be printed on standard output.
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EXAMPLE: python extract_pgsql_models.py mydb localhost 5432 reingart saraza
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"""
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# Config options
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DEBUG = False # print debug messages to STDERR
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SCHEMA = 'public' # change if not using default PostgreSQL schema
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# Constant for Field keyword parameter order (and filter):
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KWARGS = ('type', 'length', 'default', 'required', 'ondelete',
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'notnull', 'unique', 'label', 'comment')
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import sys
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def query(conn, sql, *args):
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"Execute a SQL query and return rows as a list of dicts"
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cur = conn.cursor()
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ret = []
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try:
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if DEBUG:
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print >> sys.stderr, "QUERY: ", sql % args
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cur.execute(sql, args)
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for row in cur:
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dic = {}
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for i, value in enumerate(row):
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field = cur.description[i][0]
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dic[field] = value
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if DEBUG:
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print >> sys.stderr, "RET: ", dic
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ret.append(dic)
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return ret
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finally:
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cur.close()
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def get_tables(conn, schema=SCHEMA):
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"List table names in a given schema"
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rows = query(conn, """SELECT table_name FROM information_schema.tables
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WHERE table_schema = %s
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ORDER BY table_name""", schema)
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return [row['table_name'] for row in rows]
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def get_fields(conn, table):
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"Retrieve field list for a given table"
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if DEBUG:
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print >> sys.stderr, "Processing TABLE", table
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rows = query(conn, """
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SELECT column_name, data_type,
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is_nullable,
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character_maximum_length,
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numeric_precision, numeric_precision_radix, numeric_scale,
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column_default
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FROM information_schema.columns
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WHERE table_name=%s
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ORDER BY ordinal_position""", table)
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return rows
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def define_field(conn, table, field, pks):
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"Determine field type, default value, references, etc."
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f = {}
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ref = references(conn, table, field['column_name'])
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if ref:
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f.update(ref)
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elif field['column_default'] and \
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field['column_default'].startswith("nextval") and \
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field['column_name'] in pks:
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# postgresql sequence (SERIAL) and primary key!
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f['type'] = "'id'"
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elif field['data_type'].startswith('character'):
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f['type'] = "'string'"
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if field['character_maximum_length']:
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f['length'] = field['character_maximum_length']
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elif field['data_type'] in ('text', ):
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f['type'] = "'text'"
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elif field['data_type'] in ('boolean', 'bit'):
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f['type'] = "'boolean'"
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elif field['data_type'] in ('integer', 'smallint', 'bigint'):
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f['type'] = "'integer'"
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elif field['data_type'] in ('double precision', 'real'):
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f['type'] = "'double'"
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elif field['data_type'] in ('timestamp', 'timestamp without time zone'):
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f['type'] = "'datetime'"
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elif field['data_type'] in ('date', ):
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f['type'] = "'date'"
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elif field['data_type'] in ('time', 'time without time zone'):
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f['type'] = "'time'"
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elif field['data_type'] in ('numeric', 'currency'):
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f['precision'] = field['numeric_precision']
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f['scale'] = field['numeric_scale'] or 0
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f['type'] = "'decimal({},{})'".format(f['precision'],f['scale'])
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elif field['data_type'] in ('bytea', ):
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f['type'] = "'blob'"
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elif field['data_type'] in ('point', 'lseg', 'polygon', 'unknown', 'USER-DEFINED'):
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f['type'] = "" # unsupported?
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else:
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raise RuntimeError("Data Type not supported: %s " % str(field))
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try:
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if field['column_default']:
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if field['column_default'] == "now()":
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d = "request.now"
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elif field['column_default'] == "true":
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d = "True"
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elif field['column_default'] == "false":
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d = "False"
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else:
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d = repr(eval(field['column_default']))
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f['default'] = str(d)
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except (ValueError, SyntaxError):
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pass
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except Exception, e:
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raise RuntimeError(
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"Default unsupported '%s'" % field['column_default'])
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if not field['is_nullable']:
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f['notnull'] = "True"
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comment = get_comment(conn, table, field)
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if comment is not None:
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f['comment'] = repr(comment)
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return f
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def is_unique(conn, table, field):
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"Find unique columns (incomplete support)"
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rows = query(conn, """
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SELECT information_schema.constraint_column_usage.column_name
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FROM information_schema.table_constraints
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NATURAL JOIN information_schema.constraint_column_usage
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WHERE information_schema.table_constraints.table_name=%s
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AND information_schema.constraint_column_usage.column_name=%s
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AND information_schema.table_constraints.constraint_type='UNIQUE'
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;""", table, field['column_name'])
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return rows and True or False
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def get_comment(conn, table, field):
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"Find the column comment (postgres specific)"
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rows = query(conn, """
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SELECT d.description AS comment
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FROM pg_class c
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JOIN pg_description d ON c.oid=d.objoid
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JOIN pg_attribute a ON c.oid = a.attrelid
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WHERE c.relname=%s AND a.attname=%s
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AND a.attnum = d.objsubid
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;""", table, field['column_name'])
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return rows and rows[0]['comment'] or None
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def primarykeys(conn, table):
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"Find primary keys"
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rows = query(conn, """
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SELECT information_schema.constraint_column_usage.column_name
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FROM information_schema.table_constraints
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NATURAL JOIN information_schema.constraint_column_usage
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WHERE information_schema.table_constraints.table_name=%s
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AND information_schema.table_constraints.constraint_type='PRIMARY KEY'
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;""", table)
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return [row['column_name'] for row in rows]
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def references(conn, table, field):
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"Find a FK (fails if multiple)"
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rows1 = query(conn, """
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SELECT table_name, column_name, constraint_name,
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update_rule, delete_rule, ordinal_position
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FROM information_schema.key_column_usage
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NATURAL JOIN information_schema.referential_constraints
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NATURAL JOIN information_schema.table_constraints
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WHERE information_schema.key_column_usage.table_name=%s
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AND information_schema.key_column_usage.column_name=%s
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AND information_schema.table_constraints.constraint_type='FOREIGN KEY'
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;""", table, field)
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if len(rows1) == 1:
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rows2 = query(conn, """
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SELECT table_name, column_name, *
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FROM information_schema.constraint_column_usage
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WHERE constraint_name=%s
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""", rows1[0]['constraint_name'])
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row = None
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if len(rows2) > 1:
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row = rows2[int(rows1[0]['ordinal_position']) - 1]
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keyed = True
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if len(rows2) == 1:
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row = rows2[0]
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keyed = False
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if row:
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if keyed: # THIS IS BAD, DON'T MIX "id" and primarykey!!!
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ref = {'type': "'reference %s.%s'" % (row['table_name'],
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row['column_name'])}
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else:
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ref = {'type': "'reference %s'" % (row['table_name'],)}
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if rows1[0]['delete_rule'] != "NO ACTION":
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ref['ondelete'] = repr(rows1[0]['delete_rule'])
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return ref
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elif rows2:
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raise RuntimeError("Unsupported foreign key reference: %s" %
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str(rows2))
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elif rows1:
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raise RuntimeError("Unsupported referential constraint: %s" %
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str(rows1))
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def define_table(conn, table):
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"Output single table definition"
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fields = get_fields(conn, table)
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pks = primarykeys(conn, table)
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print "db.define_table('%s'," % (table, )
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for field in fields:
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fname = field['column_name']
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fdef = define_field(conn, table, field, pks)
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if fname not in pks and is_unique(conn, table, field):
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fdef['unique'] = "True"
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if fdef['type'] == "'id'" and fname in pks:
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pks.pop(pks.index(fname))
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print " Field('%s', %s)," % (fname,
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', '.join(["%s=%s" % (k, fdef[k]) for k in KWARGS
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if k in fdef and fdef[k]]))
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if pks:
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print " primarykey=[%s]," % ", ".join(["'%s'" % pk for pk in pks])
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print " migrate=migrate)"
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print
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def define_db(conn, db, host, port, user, passwd):
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"Output database definition (model)"
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dal = 'db = DAL("postgres://%s:%s@%s:%s/%s", pool_size=10)'
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print dal % (user, passwd, host, port, db)
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print
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print "migrate = False"
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print
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for table in get_tables(conn):
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define_table(conn, table)
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if __name__ == "__main__":
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if len(sys.argv) < 6:
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print HELP
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else:
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# Parse arguments from command line:
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db, host, port, user, passwd = sys.argv[1:6]
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# Make the database connection (change driver if required)
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import psycopg2
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cnn = psycopg2.connect(database=db, host=host, port=port,
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user=user, password=passwd,
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)
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# Start model code generation:
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define_db(cnn, db, host, port, user, passwd)
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