Thuban/Model/transientdb.py

# Copyright (C) 2003 by Intevation GmbH
# Authors:
# Bernhard Herzog <[email protected]>
#
# This program is free software under the GPL (>=v2)
# Read the file COPYING coming with the software for details.

"""Database for transient data

This database is intended for data representations needed during the
lifetime of a Thuban session but which is not permanent. Examples of
this are for instance a join of two DBF files where the DBF files are
the permanent representation of the data and the join only exists in the
Thuban session and is reconstructed when the session is opened.
"""

__version__ = "$Revision$"
# $Source$
# $Id$

import os
import weakref
from sqlite import connect

from base import TitledObject

import table

sql_type_map = {
    table.FIELDTYPE_INT: "INTEGER",
    table.FIELDTYPE_STRING: "VARCHAR",
    table.FIELDTYPE_DOUBLE: "FLOAT",
    }

type_converter_map = {
    table.FIELDTYPE_INT: int,
    table.FIELDTYPE_STRING: str,
    table.FIELDTYPE_DOUBLE: float,
    }

class TransientDatabase:

    def __init__(self, filename):
        self.filename = filename
        self.conn = connect(filename)
        # Counters to produce unique table and column names
        self.num_tables = 0
        self.num_cols = 0
        # Since there's only once process using the SQLite database, we
        # might be able to get a tad more speed with default_synchronous
        # OFF. So far I haven't seen any measurable speedup, though.
        #self.execute("PRAGMA default_synchronous = OFF")

    def __del__(self):
        self.close()

    def close(self):
        if self.conn is not None:
            self.conn.close()
            self.conn = None

    def new_table_name(self):
        self.num_tables += 1
        return "Table%03d" % self.num_tables

    def new_column_name(self):
        self.num_cols += 1
        return "Col%03d" % self.num_cols

    def execute(self, *args):
        """execute the SQL statement in the database and return the result"""
        cursor = self.conn.cursor()
        cursor.execute(*args)
        result = cursor.fetchone()
        self.conn.commit()
        return result

    def cursor(self):
        return self.conn.cursor()


class ColumnReference:

    def __init__(self, name, type, internal_name):
        self.name = name
        self.type = type
        self.internal_name = internal_name


class TransientTableBase(table.OldTableInterfaceMixin):

    """Base class for tables in the transient database"""

    def __init__(self, transient_db):
        """Initialize the table for use with the given transient db"""
        self.db = transient_db
        self.tablename = self.db.new_table_name()
        self.indexed_columns = {}
        self.read_record_cursor = None
        self.read_record_last_row = None
        self.read_record_last_result = None

    def create(self, columns):
        self.columns = columns
        self.name_to_column = {}
        self.orig_names = []
        self.internal_to_orig = {}
        self.orig_to_internal = {}
        self.column_map = {}

        # Create the column objects and fill various maps and lists
        for index in range(len(self.columns)):
            col = self.columns[index]
            self.name_to_column[col.name] = col
            self.orig_names.append(col.name)
            self.internal_to_orig[col.internal_name] = col.name
            self.orig_to_internal[col.name] = col.internal_name
            self.column_map[col.name] = col
            self.column_map[index] = col

        # Build the CREATE TABLE statement and create the table in the
        # database
        table_types = ["id INTEGER PRIMARY KEY"]
        for col in self.columns:
            table_types.append("%s %s" % (col.internal_name,
                                          sql_type_map[col.type]))
        table_stmt = "CREATE TABLE %s (\n    %s\n);" % (self.tablename,
                                                   ",\n    ".join(table_types))
        self.db.execute(table_stmt)

    def transient_table(self):
        """
        Return a table whose underlying implementation is in the transient db
        """
        return self

    def ensure_index(self, column):
        """Ensure that there's an index on the given column"""
        if not column in self.indexed_columns:
            internal_name = self.orig_to_internal[column]
            indexname = "Index_%s_%s" % (self.tablename, internal_name)
            stmt = "CREATE INDEX %s ON %s (%s);" % (indexname, self.tablename,
                                                    internal_name)
            self.db.execute(stmt)
            self.indexed_columns[column] = 1

    def NumColumns(self):
        return len(self.columns)

    def NumRows(self):
        result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
        return int(result[0])

    def Columns(self):
        return self.columns

    def Column(self, col):
        return self.column_map[col]

    def HasColumn(self, col):
        """Return whether the table has a column with the given name or index
        """
        return self.column_map.has_key(col)

    def ReadRowAsDict(self, index):
        # Implementation Strategy: Executing a completely new select
        # statement every time this method is called is too slow. The
        # most important usage is to read the records more or less
        # sequentially. This happens e.g. when drawing a layer with a
        # classification where the shapes are drawn in order of the
        # shape ids. Another pattern is that the same row is requested
        # several times in a row. This happens in the table view, for
        # instance.

        # We can exploit this to make access faster by having one cursor
        # open all the time and keeping the last row read around in case
        # the same row is accessed again the next time and if the row
        # index is larger than the row we have read last we simply fetch
        # rows from the cursor until we've reached the requested row. If
        # the requested row index is smaller then we start a new cursor.

        # FIXME: So far this scheme seems to work well enough. Obvious
        # improvements would be to start the cursor at exactly the
        # requested row (should be efficient and easy to do now that the
        # id is the primary key) and to perhaps to also start a new
        # cursor if the requested index is much larger than the last row
        # so that we don't read and discard lots of the rows.

        # Check whether we have to start a new cursor
        if self.read_record_cursor is None or index <self.read_record_last_row:
            stmt = ("SELECT %s FROM %s;"
                    % (", ".join([c.internal_name for c in self.columns]),
                       self.tablename))
            self.read_record_cursor = self.db.cursor()
            self.read_record_cursor.execute(stmt)
            self.read_record_last_row = -1
            self.read_record_last_result = None

        # Now we should have a cursor at a position less than or equal
        # to the index so the following if statement will always set
        # result to a suitable value
        assert index >= self.read_record_last_row

        if index == self.read_record_last_row:
            result = self.read_record_last_result
        else:
            for i in range(index - self.read_record_last_row):
                result = self.read_record_cursor.fetchone()
                self.read_record_last_result = result
        self.read_record_last_row = index
        return dict(zip(self.orig_names, result))

    def ReadValue(self, row, col):
        """Return the value of the specified row and column

        The col parameter may be the index of the column or its name.
        """
        # Depending on the actual access patterns of the table data, it
        # might be a bit faster in some circumstances to not implement
        # this via ReadRowAsDict, but this simple implementation should
        # be fast enough for most purposes.
        return self.ReadRowAsDict(row)[self.column_map[col].name]

    def ValueRange(self, col):
        col = self.column_map[col]
        iname = col.internal_name
        min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"
                                   % (iname, iname, self.tablename))
        converter = type_converter_map[col.type]
        return (converter(min), converter(max))

    def UniqueValues(self, col):
        iname = self.column_map[col].internal_name
        cursor = self.db.cursor()
        cursor.execute("SELECT %s FROM %s GROUP BY %s;"
                       % (iname, self.tablename, iname))
        result = []
        while 1:
            row = cursor.fetchone()
            if row is None:
                break
            result.append(row[0])
        return result

    def SimpleQuery(self, left, comparison, right):
        """Return the indices of all rows that matching a condition.

        Parameters:
           left -- The column object for the left side of the comparison

           comparison -- The comparison operator as a string. It must be
                         one of '==', '!=', '<', '<=', '>=', '>'

           right -- The right hand side of the comparison. It must be
                    either a column object or a value, i.e. a string,
                    int or float.

        The return value is a sorted list of the indices of the rows
        where the condition is true.
        """
        if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
            raise ValueError("Comparison operator %r not allowed" % comparison)

        if hasattr(right, "internal_name"):
            right_template = right.internal_name
            params = ()
        else:
            right_template = "%s"
            params = (right,)

        query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
                % (self.tablename, left.internal_name, comparison,
                   right_template)

        cursor = self.db.cursor()
        cursor.execute(query, params)
        result = []
        while 1:
            row = cursor.fetchone()
            if row is None:
                break
            result.append(row[0])
        return result

    def Dependencies(self):
        """Placeholder for a method in a derived class.

        Return a sequence with the tables and other data objects that
        self depends on.
        """
        raise NotImplementedError


class TransientTable(TitledObject, TransientTableBase):

    """A Table in a transient DB that starts as the copy of a Thuban Table."""

    def __init__(self, transient_db, table):
        """Create a new table in the given transient DB as a copy of table

        The table argument can be any object implementing the Table
        interface.
        """
        TransientTableBase.__init__(self, transient_db)
        TitledObject.__init__(self, table.Title())
        self.create(table)

    def create(self, table):
        columns = []
        for col in table.Columns():
            columns.append(ColumnReference(col.name, col.type,
                                           self.db.new_column_name()))
        TransientTableBase.create(self, columns)

        # copy the input table to the transient db

        # A key to insert to use for the formatting of the insert
        # statement. The key must not be equal to any of the column
        # names so we construct one by building a string of x's that is
        # longer than any of the column names
        id_key = max([len(col.name) for col in self.columns]) * "x"

        insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
                               % (self.tablename,
                                  ", ".join([col.internal_name
                                             for col in self.columns]),
                                  id_key,
                                  ", ".join(["%%(%s)s" % col.name
                                             for col in self.columns]))
        cursor = self.db.cursor()
        for i in range(table.NumRows()):
            row = table.ReadRowAsDict(i)
            row[id_key] = i
            cursor.execute(insert_template, row)
        self.db.conn.commit()


class TransientJoinedTable(TitledObject, TransientTableBase):

    """A Table in the transient DB that contains a join of two tables"""

    def __init__(self, transient_db, left_table, left_field,
                 right_table, right_field = None, outer_join = False):
        """Create a new table in the transient DB as a join of two tables.

        Both input tables, left_table and right_table must have a
        transient_table method that returns a table object for a table
        in the transient database. The join is performed on the condition
        that the value of the left_field column the the left table is
        equal to the value of the right_field in the right_table.

        The joined table contains all columns of the input tables with
        one exception: Any column in the right_table with the same name
        as one of the columns in the left_table will be omitted. This is
        somewhat of an implementation detail, but is done so that the
        column names of the joined table can be the same as the column
        names of the input tables without having to create prefixes.
        """
        TransientTableBase.__init__(self, transient_db)
        self.dependencies = (left_table, right_table)
        self.left_table = left_table.transient_table()
        self.left_field = left_field
        self.right_table = right_table.transient_table()
        if right_field:
            self.right_field = right_field
        else:
            self.right_field = self.left_field
        self.outer_join = outer_join

        title = "Join of %(left)s and %(right)s" \
                % {"left": self.left_table.Title(),
                   "right": self.right_table.Title()}
        TitledObject.__init__(self, title)

        self.create()

    def create(self):
        """Internal: Create the table with the joined data"""
        self.tablename = self.db.new_table_name()

        self.right_table.ensure_index(self.right_field)

        # Coalesce the column information
        visited = {}
        columns = []
        for col in self.left_table.columns + self.right_table.columns:
            if col.name in visited:
                # We can't allow multiple columns with the same original
                # name, so omit this one. FIXME: There should be a
                # better solution.
                continue
            columns.append(col)
        TransientTableBase.create(self, columns)

        # Copy the joined data to the table.
        internal_names = [col.internal_name for col in self.columns]
        if self.outer_join:
            join_operator = 'LEFT OUTER JOIN'
        else:
            join_operator = 'JOIN'
        stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
                " %s %s ON %s = %s;"
                % (self.tablename,
                   ", ".join(internal_names),
                   self.left_table.tablename,
                   ", ".join(internal_names),
                   self.left_table.tablename,
                   join_operator,
                   self.right_table.tablename,
                   self.orig_to_internal[self.left_field],
                   self.orig_to_internal[self.right_field]))
        self.db.execute(stmt)

    def Dependencies(self):
        """Return a tuple with the two tables the join depends on."""
        return self.dependencies


class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):

    """Table that copies data to a transient table on demand.

    The AutoTransientTable takes another table as input and copies data
    to a table in a TransientDatabase instance on demand.
    """

    def __init__(self, transient_db, table):
        TitledObject.__init__(self, table.Title())
        self.transient_db = transient_db
        self.table = table
        self.t_table = None

    def Columns(self):
        return self.table.Columns()

    def Column(self, col):
        return self.table.Column(col)

    def HasColumn(self, col):
        """Return whether the table has a column with the given name or index
        """
        return self.table.HasColumn(col)

    def NumRows(self):
        return self.table.NumRows()

    def NumColumns(self):
        return self.table.NumColumns()

    def ReadRowAsDict(self, record):
        """Return the record no. record as a dict mapping field names to values
        """
        if self.t_table is not None:
            return self.t_table.ReadRowAsDict(record)
        else:
            return self.table.ReadRowAsDict(record)

    def ReadValue(self, row, col):
        """Return the value of the specified row and column

        The col parameter may be the index of the column or its name.
        """
        if self.t_table is not None:
            return self.t_table.ReadValue(row, col)
        else:
            return self.table.ReadValue(row, col)

    def copy_to_transient(self):
        """Internal: Create a transient table and copy the data into it"""
        self.t_table = TransientTable(self.transient_db, self)

    def transient_table(self):
        """
        Return a table whose underlying implementation is in the transient db
        """
        if self.t_table is None:
            self.copy_to_transient()
        return self.t_table

    def ValueRange(self, col):
        if self.t_table is None:
            self.copy_to_transient()
        return self.t_table.ValueRange(col)

    def UniqueValues(self, col):
        if self.t_table is None:
            self.copy_to_transient()
        return self.t_table.UniqueValues(col)

    def SimpleQuery(self, left, comparison, right):
        if self.t_table is None:
            self.copy_to_transient()
        # Make sure to use the column object of the transient table. The
        # left argument is always a column object so we can just ask the
        # t_table for the right object.
        if hasattr(right, "name"):
            return self.t_table.SimpleQuery(self.t_table.Column(left.name),
                                            comparison, 
                                            self.t_table.Column(right.name))
        else:
            return self.t_table.SimpleQuery(self.t_table.Column(left.name),
                                            comparison, right)

    def Dependencies(self):
        """Return a tuple containing the original table"""
        return (self.table,)
1	# Copyright (C) 2003 by Intevation GmbH
2	# Authors:
3	# Bernhard Herzog <[email protected]>
4	#
5	# This program is free software under the GPL (>=v2)
6	# Read the file COPYING coming with the software for details.
7
8	"""Database for transient data
9
10	This database is intended for data representations needed during the
11	lifetime of a Thuban session but which is not permanent. Examples of
12	this are for instance a join of two DBF files where the DBF files are
13	the permanent representation of the data and the join only exists in the
14	Thuban session and is reconstructed when the session is opened.
15	"""
16
17	__version__ = "$Revision$"
18	# $Source$
19	# $Id$
20
21	import os
22	import weakref
23	from sqlite import connect
24
25	from base import TitledObject
26
27	import table
28
29	sql_type_map = {
30	table.FIELDTYPE_INT: "INTEGER",
31	table.FIELDTYPE_STRING: "VARCHAR",
32	table.FIELDTYPE_DOUBLE: "FLOAT",
33	}
34
35	type_converter_map = {
36	table.FIELDTYPE_INT: int,
37	table.FIELDTYPE_STRING: str,
38	table.FIELDTYPE_DOUBLE: float,
39	}
40
41	class TransientDatabase:
42
43	def __init__(self, filename):
44	self.filename = filename
45	self.conn = connect(filename)
46	# Counters to produce unique table and column names
47	self.num_tables = 0
48	self.num_cols = 0
49	# Since there's only once process using the SQLite database, we
50	# might be able to get a tad more speed with default_synchronous
51	# OFF. So far I haven't seen any measurable speedup, though.
52	#self.execute("PRAGMA default_synchronous = OFF")
53
54	def __del__(self):
55	self.close()
56
57	def close(self):
58	if self.conn is not None:
59	self.conn.close()
60	self.conn = None
61
62	def new_table_name(self):
63	self.num_tables += 1
64	return "Table%03d" % self.num_tables
65
66	def new_column_name(self):
67	self.num_cols += 1
68	return "Col%03d" % self.num_cols
69
70	def execute(self, *args):
71	"""execute the SQL statement in the database and return the result"""
72	cursor = self.conn.cursor()
73	cursor.execute(*args)
74	result = cursor.fetchone()
75	self.conn.commit()
76	return result
77
78	def cursor(self):
79	return self.conn.cursor()
80
81
82	class ColumnReference:
83
84	def __init__(self, name, type, internal_name):
85	self.name = name
86	self.type = type
87	self.internal_name = internal_name
88
89
90	class TransientTableBase(table.OldTableInterfaceMixin):
91
92	"""Base class for tables in the transient database"""
93
94	def __init__(self, transient_db):
95	"""Initialize the table for use with the given transient db"""
96	self.db = transient_db
97	self.tablename = self.db.new_table_name()
98	self.indexed_columns = {}
99	self.read_record_cursor = None
100	self.read_record_last_row = None
101	self.read_record_last_result = None
102
103	def create(self, columns):
104	self.columns = columns
105	self.name_to_column = {}
106	self.orig_names = []
107	self.internal_to_orig = {}
108	self.orig_to_internal = {}
109	self.column_map = {}
110
111	# Create the column objects and fill various maps and lists
112	for index in range(len(self.columns)):
113	col = self.columns[index]
114	self.name_to_column[col.name] = col
115	self.orig_names.append(col.name)
116	self.internal_to_orig[col.internal_name] = col.name
117	self.orig_to_internal[col.name] = col.internal_name
118	self.column_map[col.name] = col
119	self.column_map[index] = col
120
121	# Build the CREATE TABLE statement and create the table in the
122	# database
123	table_types = ["id INTEGER PRIMARY KEY"]
124	for col in self.columns:
125	table_types.append("%s %s" % (col.internal_name,
126	sql_type_map[col.type]))
127	table_stmt = "CREATE TABLE %s (\n %s\n);" % (self.tablename,
128	",\n ".join(table_types))
129	self.db.execute(table_stmt)
130
131	def transient_table(self):
132	"""
133	Return a table whose underlying implementation is in the transient db
134	"""
135	return self
136
137	def ensure_index(self, column):
138	"""Ensure that there's an index on the given column"""
139	if not column in self.indexed_columns:
140	internal_name = self.orig_to_internal[column]
141	indexname = "Index_%s_%s" % (self.tablename, internal_name)
142	stmt = "CREATE INDEX %s ON %s (%s);" % (indexname, self.tablename,
143	internal_name)
144	self.db.execute(stmt)
145	self.indexed_columns[column] = 1
146
147	def NumColumns(self):
148	return len(self.columns)
149
150	def NumRows(self):
151	result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
152	return int(result[0])
153
154	def Columns(self):
155	return self.columns
156
157	def Column(self, col):
158	return self.column_map[col]
159
160	def HasColumn(self, col):
161	"""Return whether the table has a column with the given name or index
162	"""
163	return self.column_map.has_key(col)
164
165	def ReadRowAsDict(self, index):
166	# Implementation Strategy: Executing a completely new select
167	# statement every time this method is called is too slow. The
168	# most important usage is to read the records more or less
169	# sequentially. This happens e.g. when drawing a layer with a
170	# classification where the shapes are drawn in order of the
171	# shape ids. Another pattern is that the same row is requested
172	# several times in a row. This happens in the table view, for
173	# instance.
174
175	# We can exploit this to make access faster by having one cursor
176	# open all the time and keeping the last row read around in case
177	# the same row is accessed again the next time and if the row
178	# index is larger than the row we have read last we simply fetch
179	# rows from the cursor until we've reached the requested row. If
180	# the requested row index is smaller then we start a new cursor.
181
182	# FIXME: So far this scheme seems to work well enough. Obvious
183	# improvements would be to start the cursor at exactly the
184	# requested row (should be efficient and easy to do now that the
185	# id is the primary key) and to perhaps to also start a new
186	# cursor if the requested index is much larger than the last row
187	# so that we don't read and discard lots of the rows.
188
189	# Check whether we have to start a new cursor
190	if self.read_record_cursor is None or index <self.read_record_last_row:
191	stmt = ("SELECT %s FROM %s;"
192	% (", ".join([c.internal_name for c in self.columns]),
193	self.tablename))
194	self.read_record_cursor = self.db.cursor()
195	self.read_record_cursor.execute(stmt)
196	self.read_record_last_row = -1
197	self.read_record_last_result = None
198
199	# Now we should have a cursor at a position less than or equal
200	# to the index so the following if statement will always set
201	# result to a suitable value
202	assert index >= self.read_record_last_row
203
204	if index == self.read_record_last_row:
205	result = self.read_record_last_result
206	else:
207	for i in range(index - self.read_record_last_row):
208	result = self.read_record_cursor.fetchone()
209	self.read_record_last_result = result
210	self.read_record_last_row = index
211	return dict(zip(self.orig_names, result))
212
213	def ReadValue(self, row, col):
214	"""Return the value of the specified row and column
215
216	The col parameter may be the index of the column or its name.
217	"""
218	# Depending on the actual access patterns of the table data, it
219	# might be a bit faster in some circumstances to not implement
220	# this via ReadRowAsDict, but this simple implementation should
221	# be fast enough for most purposes.
222	return self.ReadRowAsDict(row)[self.column_map[col].name]
223
224	def ValueRange(self, col):
225	col = self.column_map[col]
226	iname = col.internal_name
227	min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"
228	% (iname, iname, self.tablename))
229	converter = type_converter_map[col.type]
230	return (converter(min), converter(max))
231
232	def UniqueValues(self, col):
233	iname = self.column_map[col].internal_name
234	cursor = self.db.cursor()
235	cursor.execute("SELECT %s FROM %s GROUP BY %s;"
236	% (iname, self.tablename, iname))
237	result = []
238	while 1:
239	row = cursor.fetchone()
240	if row is None:
241	break
242	result.append(row[0])
243	return result
244
245	def SimpleQuery(self, left, comparison, right):
246	"""Return the indices of all rows that matching a condition.
247
248	Parameters:
249	left -- The column object for the left side of the comparison
250
251	comparison -- The comparison operator as a string. It must be
252	one of '==', '!=', '<', '<=', '>=', '>'
253
254	right -- The right hand side of the comparison. It must be
255	either a column object or a value, i.e. a string,
256	int or float.
257
258	The return value is a sorted list of the indices of the rows
259	where the condition is true.
260	"""
261	if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
262	raise ValueError("Comparison operator %r not allowed" % comparison)
263
264	if hasattr(right, "internal_name"):
265	right_template = right.internal_name
266	params = ()
267	else:
268	right_template = "%s"
269	params = (right,)
270
271	query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
272	% (self.tablename, left.internal_name, comparison,
273	right_template)
274
275	cursor = self.db.cursor()
276	cursor.execute(query, params)
277	result = []
278	while 1:
279	row = cursor.fetchone()
280	if row is None:
281	break
282	result.append(row[0])
283	return result
284
285	def Dependencies(self):
286	"""Placeholder for a method in a derived class.
287
288	Return a sequence with the tables and other data objects that
289	self depends on.
290	"""
291	raise NotImplementedError
292
293
294	class TransientTable(TitledObject, TransientTableBase):
295
296	"""A Table in a transient DB that starts as the copy of a Thuban Table."""
297
298	def __init__(self, transient_db, table):
299	"""Create a new table in the given transient DB as a copy of table
300
301	The table argument can be any object implementing the Table
302	interface.
303	"""
304	TransientTableBase.__init__(self, transient_db)
305	TitledObject.__init__(self, table.Title())
306	self.create(table)
307
308	def create(self, table):
309	columns = []
310	for col in table.Columns():
311	columns.append(ColumnReference(col.name, col.type,
312	self.db.new_column_name()))
313	TransientTableBase.create(self, columns)
314
315	# copy the input table to the transient db
316
317	# A key to insert to use for the formatting of the insert
318	# statement. The key must not be equal to any of the column
319	# names so we construct one by building a string of x's that is
320	# longer than any of the column names
321	id_key = max([len(col.name) for col in self.columns]) * "x"
322
323	insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
324	% (self.tablename,
325	", ".join([col.internal_name
326	for col in self.columns]),
327	id_key,
328	", ".join(["%%(%s)s" % col.name
329	for col in self.columns]))
330	cursor = self.db.cursor()
331	for i in range(table.NumRows()):
332	row = table.ReadRowAsDict(i)
333	row[id_key] = i
334	cursor.execute(insert_template, row)
335	self.db.conn.commit()
336
337
338
339	class TransientJoinedTable(TitledObject, TransientTableBase):
340
341	"""A Table in the transient DB that contains a join of two tables"""
342
343	def __init__(self, transient_db, left_table, left_field,
344	right_table, right_field = None, outer_join = False):
345	"""Create a new table in the transient DB as a join of two tables.
346
347	Both input tables, left_table and right_table must have a
348	transient_table method that returns a table object for a table
349	in the transient database. The join is performed on the condition
350	that the value of the left_field column the the left table is
351	equal to the value of the right_field in the right_table.
352
353	The joined table contains all columns of the input tables with
354	one exception: Any column in the right_table with the same name
355	as one of the columns in the left_table will be omitted. This is
356	somewhat of an implementation detail, but is done so that the
357	column names of the joined table can be the same as the column
358	names of the input tables without having to create prefixes.
359	"""
360	TransientTableBase.__init__(self, transient_db)
361	self.dependencies = (left_table, right_table)
362	self.left_table = left_table.transient_table()
363	self.left_field = left_field
364	self.right_table = right_table.transient_table()
365	if right_field:
366	self.right_field = right_field
367	else:
368	self.right_field = self.left_field
369	self.outer_join = outer_join
370
371	title = "Join of %(left)s and %(right)s" \
372	% {"left": self.left_table.Title(),
373	"right": self.right_table.Title()}
374	TitledObject.__init__(self, title)
375
376	self.create()
377
378	def create(self):
379	"""Internal: Create the table with the joined data"""
380	self.tablename = self.db.new_table_name()
381
382	self.right_table.ensure_index(self.right_field)
383
384	# Coalesce the column information
385	visited = {}
386	columns = []
387	for col in self.left_table.columns + self.right_table.columns:
388	if col.name in visited:
389	# We can't allow multiple columns with the same original
390	# name, so omit this one. FIXME: There should be a
391	# better solution.
392	continue
393	columns.append(col)
394	TransientTableBase.create(self, columns)
395
396	# Copy the joined data to the table.
397	internal_names = [col.internal_name for col in self.columns]
398	if self.outer_join:
399	join_operator = 'LEFT OUTER JOIN'
400	else:
401	join_operator = 'JOIN'
402	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
403	" %s %s ON %s = %s;"
404	% (self.tablename,
405	", ".join(internal_names),
406	self.left_table.tablename,
407	", ".join(internal_names),
408	self.left_table.tablename,
409	join_operator,
410	self.right_table.tablename,
411	self.orig_to_internal[self.left_field],
412	self.orig_to_internal[self.right_field]))
413	self.db.execute(stmt)
414
415	def Dependencies(self):
416	"""Return a tuple with the two tables the join depends on."""
417	return self.dependencies
418
419
420	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
421
422	"""Table that copies data to a transient table on demand.
423
424	The AutoTransientTable takes another table as input and copies data
425	to a table in a TransientDatabase instance on demand.
426	"""
427
428	def __init__(self, transient_db, table):
429	TitledObject.__init__(self, table.Title())
430	self.transient_db = transient_db
431	self.table = table
432	self.t_table = None
433
434	def Columns(self):
435	return self.table.Columns()
436
437	def Column(self, col):
438	return self.table.Column(col)
439
440	def HasColumn(self, col):
441	"""Return whether the table has a column with the given name or index
442	"""
443	return self.table.HasColumn(col)
444
445	def NumRows(self):
446	return self.table.NumRows()
447
448	def NumColumns(self):
449	return self.table.NumColumns()
450
451	def ReadRowAsDict(self, record):
452	"""Return the record no. record as a dict mapping field names to values
453	"""
454	if self.t_table is not None:
455	return self.t_table.ReadRowAsDict(record)
456	else:
457	return self.table.ReadRowAsDict(record)
458
459	def ReadValue(self, row, col):
460	"""Return the value of the specified row and column
461
462	The col parameter may be the index of the column or its name.
463	"""
464	if self.t_table is not None:
465	return self.t_table.ReadValue(row, col)
466	else:
467	return self.table.ReadValue(row, col)
468
469	def copy_to_transient(self):
470	"""Internal: Create a transient table and copy the data into it"""
471	self.t_table = TransientTable(self.transient_db, self)
472
473	def transient_table(self):
474	"""
475	Return a table whose underlying implementation is in the transient db
476	"""
477	if self.t_table is None:
478	self.copy_to_transient()
479	return self.t_table
480
481	def ValueRange(self, col):
482	if self.t_table is None:
483	self.copy_to_transient()
484	return self.t_table.ValueRange(col)
485
486	def UniqueValues(self, col):
487	if self.t_table is None:
488	self.copy_to_transient()
489	return self.t_table.UniqueValues(col)
490
491	def SimpleQuery(self, left, comparison, right):
492	if self.t_table is None:
493	self.copy_to_transient()
494	# Make sure to use the column object of the transient table. The
495	# left argument is always a column object so we can just ask the
496	# t_table for the right object.
497	if hasattr(right, "name"):
498	return self.t_table.SimpleQuery(self.t_table.Column(left.name),
499	comparison,
500	self.t_table.Column(right.name))
501	else:
502	return self.t_table.SimpleQuery(self.t_table.Column(left.name),
503	comparison, right)
504
505	def Dependencies(self):
506	"""Return a tuple containing the original table"""
507	return (self.table,)
Name	Value
svn:eol-style	native
svn:keywords	Author Date Id Revision