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 Width(self, col):
        """Return the maximum width of values in the column

        The return value is the the maximum length of string representation 
        of the values in the column (represented by index or name)."""
        max = 0
        
        type  = self.column_map[col].type
        iname = self.column_map[col].internal_name
        cursor = self.db.cursor()
        cursor.execute("SELECT %s FROM %s;" % (iname, self.tablename))
        values = [ i[0] for i in cursor.fetchall()]
        if not values:
            return None

        if type == sql_type_map[table.FIELDTYPE_DOUBLE]:
            format = "%.12f"
        elif type == sql_type_map[table.FIELDTYPE_INT]:
            format = "%d"
        else:
            format = "%s"
        for value in values:
            if value is None: continue
            l = len(format % value)
            if l > max:
                max = l

        return max

    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,)

    def Width(self, col):
        return self.table.Width(col)
1	bh	765	# 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	jan	1020	from base import TitledObject
26
27	bh	765	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	bh	777	if self.conn is not None:
59	bh	765	self.conn.close()
60	bh	777	self.conn = None
61	bh	765
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	bh	818	class TransientTableBase(table.OldTableInterfaceMixin):
91	bh	765
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	bh	785	self.read_record_last_result = None
102	bh	765
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	bh	818	self.column_map = {}
110	bh	765
111			# Create the column objects and fill various maps and lists
112	bh	818	for index in range(len(self.columns)):
113			col = self.columns[index]
114	bh	765	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	bh	818	self.column_map[col.name] = col
119			self.column_map[index] = col
120	bh	765
121			# Build the CREATE TABLE statement and create the table in the
122			# database
123	bh	841	table_types = ["id INTEGER PRIMARY KEY"]
124	bh	765	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	bh	818	def NumColumns(self):
148	bh	765	return len(self.columns)
149
150	bh	818	def NumRows(self):
151	bh	765	result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
152			return int(result[0])
153
154	bh	818	def Columns(self):
155			return self.columns
156
157			def Column(self, col):
158			return self.column_map[col]
159
160	bh	839	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	bh	818	def ReadRowAsDict(self, index):
166	bh	849	# 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	bh	765	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	bh	785	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	bh	818	result = self.read_record_last_result
206	bh	785	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	bh	765	self.read_record_last_row = index
211	bh	785	return dict(zip(self.orig_names, result))
212	bh	765
213	bh	849	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	bh	818	def ValueRange(self, col):
225			col = self.column_map[col]
226	bh	765	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	bh	818	return (converter(min), converter(max))
231	bh	765
232	bh	818	def UniqueValues(self, col):
233			iname = self.column_map[col].internal_name
234	bh	765	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	frank	1026	def Width(self, col):
246			"""Return the maximum width of values in the column
247
248			The return value is the the maximum length of string representation
249			of the values in the column (represented by index or name)."""
250			max = 0
251
252			type = self.column_map[col].type
253			iname = self.column_map[col].internal_name
254			cursor = self.db.cursor()
255			cursor.execute("SELECT %s FROM %s;" % (iname, self.tablename))
256			values = [ i[0] for i in cursor.fetchall()]
257			if not values:
258			return None
259
260			if type == sql_type_map[table.FIELDTYPE_DOUBLE]:
261	bh	1043	format = "%.12f"
262	frank	1026	elif type == sql_type_map[table.FIELDTYPE_INT]:
263			format = "%d"
264			else:
265			format = "%s"
266			for value in values:
267			if value is None: continue
268			l = len(format % value)
269			if l > max:
270			max = l
271
272			return max
273
274	bh	841	def SimpleQuery(self, left, comparison, right):
275			"""Return the indices of all rows that matching a condition.
276	bh	765
277	bh	841	Parameters:
278			left -- The column object for the left side of the comparison
279
280			comparison -- The comparison operator as a string. It must be
281			one of '==', '!=', '<', '<=', '>=', '>'
282
283			right -- The right hand side of the comparison. It must be
284			either a column object or a value, i.e. a string,
285			int or float.
286
287			The return value is a sorted list of the indices of the rows
288			where the condition is true.
289			"""
290			if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
291			raise ValueError("Comparison operator %r not allowed" % comparison)
292
293			if hasattr(right, "internal_name"):
294			right_template = right.internal_name
295			params = ()
296			else:
297			right_template = "%s"
298			params = (right,)
299
300			query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
301			% (self.tablename, left.internal_name, comparison,
302			right_template)
303
304			cursor = self.db.cursor()
305			cursor.execute(query, params)
306			result = []
307			while 1:
308			row = cursor.fetchone()
309			if row is None:
310			break
311			result.append(row[0])
312			return result
313
314	bh	984	def Dependencies(self):
315			"""Placeholder for a method in a derived class.
316	bh	841
317	bh	984	Return a sequence with the tables and other data objects that
318			self depends on.
319			"""
320			raise NotImplementedError
321
322
323	jan	1020	class TransientTable(TitledObject, TransientTableBase):
324	bh	765
325			"""A Table in a transient DB that starts as the copy of a Thuban Table."""
326
327			def __init__(self, transient_db, table):
328			"""Create a new table in the given transient DB as a copy of table
329
330			The table argument can be any object implementing the Table
331			interface.
332			"""
333			TransientTableBase.__init__(self, transient_db)
334	jan	1020	TitledObject.__init__(self, table.Title())
335	bh	765	self.create(table)
336
337			def create(self, table):
338			columns = []
339	bh	818	for col in table.Columns():
340			columns.append(ColumnReference(col.name, col.type,
341	bh	765	self.db.new_column_name()))
342			TransientTableBase.create(self, columns)
343
344			# copy the input table to the transient db
345	bh	841
346			# A key to insert to use for the formatting of the insert
347			# statement. The key must not be equal to any of the column
348			# names so we construct one by building a string of x's that is
349			# longer than any of the column names
350			id_key = max([len(col.name) for col in self.columns]) * "x"
351
352			insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
353	bh	765	% (self.tablename,
354			", ".join([col.internal_name
355			for col in self.columns]),
356	bh	841	id_key,
357	bh	765	", ".join(["%%(%s)s" % col.name
358			for col in self.columns]))
359			cursor = self.db.cursor()
360	bh	818	for i in range(table.NumRows()):
361	bh	841	row = table.ReadRowAsDict(i)
362			row[id_key] = i
363			cursor.execute(insert_template, row)
364	bh	765	self.db.conn.commit()
365
366
367
368	jan	1020	class TransientJoinedTable(TitledObject, TransientTableBase):
369	bh	765
370			"""A Table in the transient DB that contains a join of two tables"""
371
372			def __init__(self, transient_db, left_table, left_field,
373	frank	1009	right_table, right_field = None, outer_join = False):
374	bh	765	"""Create a new table in the transient DB as a join of two tables.
375
376			Both input tables, left_table and right_table must have a
377			transient_table method that returns a table object for a table
378	frank	1002	in the transient database. The join is performed on the condition
379	bh	765	that the value of the left_field column the the left table is
380			equal to the value of the right_field in the right_table.
381
382			The joined table contains all columns of the input tables with
383			one exception: Any column in the right_table with the same name
384			as one of the columns in the left_table will be omitted. This is
385			somewhat of an implementation detail, but is done so that the
386			column names of the joined table can be the same as the column
387			names of the input tables without having to create prefixes.
388			"""
389			TransientTableBase.__init__(self, transient_db)
390	bh	984	self.dependencies = (left_table, right_table)
391	bh	765	self.left_table = left_table.transient_table()
392			self.left_field = left_field
393			self.right_table = right_table.transient_table()
394			if right_field:
395			self.right_field = right_field
396			else:
397			self.right_field = self.left_field
398	frank	1009	self.outer_join = outer_join
399	jan	1020
400			title = "Join of %(left)s and %(right)s" \
401			% {"left": self.left_table.Title(),
402			"right": self.right_table.Title()}
403			TitledObject.__init__(self, title)
404
405	bh	765	self.create()
406
407			def create(self):
408			"""Internal: Create the table with the joined data"""
409			self.tablename = self.db.new_table_name()
410
411			self.right_table.ensure_index(self.right_field)
412
413			# Coalesce the column information
414			visited = {}
415			columns = []
416			for col in self.left_table.columns + self.right_table.columns:
417			if col.name in visited:
418	bh	841	# We can't allow multiple columns with the same original
419			# name, so omit this one. FIXME: There should be a
420			# better solution.
421	bh	765	continue
422			columns.append(col)
423			TransientTableBase.create(self, columns)
424
425			# Copy the joined data to the table.
426			internal_names = [col.internal_name for col in self.columns]
427	frank	1009	if self.outer_join:
428			join_operator = 'LEFT OUTER JOIN'
429			else:
430			join_operator = 'JOIN'
431	bh	841	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
432	frank	1009	" %s %s ON %s = %s;"
433	bh	841	% (self.tablename,
434			", ".join(internal_names),
435			self.left_table.tablename,
436			", ".join(internal_names),
437			self.left_table.tablename,
438	frank	1009	join_operator,
439	bh	841	self.right_table.tablename,
440			self.orig_to_internal[self.left_field],
441			self.orig_to_internal[self.right_field]))
442	bh	765	self.db.execute(stmt)
443
444	bh	984	def Dependencies(self):
445			"""Return a tuple with the two tables the join depends on."""
446			return self.dependencies
447	bh	765
448	bh	984
449	jan	1020	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
450	bh	765
451			"""Table that copies data to a transient table on demand.
452
453			The AutoTransientTable takes another table as input and copies data
454			to a table in a TransientDatabase instance on demand.
455			"""
456
457			def __init__(self, transient_db, table):
458	jan	1020	TitledObject.__init__(self, table.Title())
459	bh	765	self.transient_db = transient_db
460			self.table = table
461			self.t_table = None
462
463	bh	818	def Columns(self):
464			return self.table.Columns()
465	bh	765
466	bh	818	def Column(self, col):
467			return self.table.Column(col)
468	bh	765
469	bh	839	def HasColumn(self, col):
470			"""Return whether the table has a column with the given name or index
471			"""
472			return self.table.HasColumn(col)
473
474	bh	818	def NumRows(self):
475			return self.table.NumRows()
476	bh	765
477	bh	818	def NumColumns(self):
478			return self.table.NumColumns()
479	bh	765
480	bh	818	def ReadRowAsDict(self, record):
481	bh	765	"""Return the record no. record as a dict mapping field names to values
482			"""
483			if self.t_table is not None:
484	bh	839	return self.t_table.ReadRowAsDict(record)
485	bh	765	else:
486	bh	818	return self.table.ReadRowAsDict(record)
487	bh	765
488	bh	849	def ReadValue(self, row, col):
489			"""Return the value of the specified row and column
490
491			The col parameter may be the index of the column or its name.
492			"""
493			if self.t_table is not None:
494			return self.t_table.ReadValue(row, col)
495			else:
496			return self.table.ReadValue(row, col)
497
498	bh	765	def copy_to_transient(self):
499			"""Internal: Create a transient table and copy the data into it"""
500			self.t_table = TransientTable(self.transient_db, self)
501
502			def transient_table(self):
503			"""
504			Return a table whose underlying implementation is in the transient db
505			"""
506			if self.t_table is None:
507			self.copy_to_transient()
508			return self.t_table
509
510	bh	818	def ValueRange(self, col):
511	bh	765	if self.t_table is None:
512			self.copy_to_transient()
513	bh	839	return self.t_table.ValueRange(col)
514	bh	765
515	bh	839	def UniqueValues(self, col):
516	bh	765	if self.t_table is None:
517			self.copy_to_transient()
518	bh	839	return self.t_table.UniqueValues(col)
519	bh	844
520			def SimpleQuery(self, left, comparison, right):
521			if self.t_table is None:
522			self.copy_to_transient()
523			# Make sure to use the column object of the transient table. The
524			# left argument is always a column object so we can just ask the
525			# t_table for the right object.
526	jonathan	933	if hasattr(right, "name"):
527			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
528			comparison,
529			self.t_table.Column(right.name))
530			else:
531			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
532			comparison, right)
533	bh	984
534			def Dependencies(self):
535			"""Return a tuple containing the original table"""
536			return (self.table,)
537	frank	1026
538	bh	1043	def Width(self, col):
539			return self.table.Width(col)
Name	Value
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