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)

        # determine the internal column names to join on before
        # coalescing the column information because if the external
        # column names are the same they will be mapped to the same
        # internal name afterwards.
        internal_left_col = self.left_table.orig_to_internal[self.left_field]
        internal_right_col = self.right_table.orig_to_internal[self.right_field]

        # Coalesce the column information
        visited = {}
        columns = []
        newcolumns = []
        for table, col in (
            [ (self.left_table.tablename, c) for c in self.left_table.columns ] 
            + [ (self.right_table.tablename, c) for c in self.right_table.columns]):
            if col.name in visited:
                if col.name == self.left_field:
                    continue
                else:
                    # We can't allow multiple columns with the same original
                    # name, so append '_' to this one until it is unique. 
                    # FIXME: There should be a better solution. 
                    while col.name in visited:
                        col.name = col.name + '_'
            columns.append((table, col))
            newcol = ColumnReference(col.name, col.type,
                                        "Col%03d" % (len(newcolumns)+1))
            newcolumns.append(newcol)
            visited[col.name] = 1
        TransientTableBase.create(self, newcolumns)

        # Copy the joined data to the table.
        newinternal_names = [col.internal_name for col in self.columns]
        internal_references = ["%s.%s" % (table, col.internal_name) 
                                                    for table, col in 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 = %s.%s;"
                % (self.tablename,
                   ", ".join(newinternal_names),
                   self.left_table.tablename,
                   ", ".join(internal_references),
                   self.left_table.tablename,
                   join_operator,
                   self.right_table.tablename,
                   self.left_table.tablename,
                   internal_left_col,
                   self.right_table.tablename,
                   internal_right_col))
        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	bh	1328	# determine the internal column names to join on before
414			# coalescing the column information because if the external
415			# column names are the same they will be mapped to the same
416			# internal name afterwards.
417			internal_left_col = self.left_table.orig_to_internal[self.left_field]
418	frank	1333	internal_right_col = self.right_table.orig_to_internal[self.right_field]
419	bh	1328
420	bh	765	# Coalesce the column information
421			visited = {}
422			columns = []
423	frank	1333	newcolumns = []
424			for table, col in (
425			[ (self.left_table.tablename, c) for c in self.left_table.columns ]
426			+ [ (self.right_table.tablename, c) for c in self.right_table.columns]):
427	bh	765	if col.name in visited:
428	frank	1333	if col.name == self.left_field:
429			continue
430			else:
431			# We can't allow multiple columns with the same original
432			# name, so append '_' to this one until it is unique.
433			# FIXME: There should be a better solution.
434			while col.name in visited:
435			col.name = col.name + '_'
436			columns.append((table, col))
437			newcol = ColumnReference(col.name, col.type,
438			"Col%03d" % (len(newcolumns)+1))
439			newcolumns.append(newcol)
440	bh	1328	visited[col.name] = 1
441	frank	1333	TransientTableBase.create(self, newcolumns)
442	bh	765
443			# Copy the joined data to the table.
444	frank	1333	newinternal_names = [col.internal_name for col in self.columns]
445			internal_references = ["%s.%s" % (table, col.internal_name)
446			for table, col in columns]
447	frank	1009	if self.outer_join:
448			join_operator = 'LEFT OUTER JOIN'
449			else:
450			join_operator = 'JOIN'
451	bh	841	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
452	frank	1333	" %s %s ON %s.%s = %s.%s;"
453	bh	841	% (self.tablename,
454	frank	1333	", ".join(newinternal_names),
455	bh	841	self.left_table.tablename,
456	frank	1333	", ".join(internal_references),
457	bh	841	self.left_table.tablename,
458	frank	1009	join_operator,
459	bh	841	self.right_table.tablename,
460	frank	1333	self.left_table.tablename,
461	bh	1328	internal_left_col,
462	frank	1333	self.right_table.tablename,
463	bh	1328	internal_right_col))
464	bh	765	self.db.execute(stmt)
465
466	bh	984	def Dependencies(self):
467			"""Return a tuple with the two tables the join depends on."""
468			return self.dependencies
469	bh	765
470	bh	984
471	jan	1020	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
472	bh	765
473			"""Table that copies data to a transient table on demand.
474
475			The AutoTransientTable takes another table as input and copies data
476			to a table in a TransientDatabase instance on demand.
477			"""
478
479			def __init__(self, transient_db, table):
480	jan	1020	TitledObject.__init__(self, table.Title())
481	bh	765	self.transient_db = transient_db
482			self.table = table
483			self.t_table = None
484
485	bh	818	def Columns(self):
486			return self.table.Columns()
487	bh	765
488	bh	818	def Column(self, col):
489			return self.table.Column(col)
490	bh	765
491	bh	839	def HasColumn(self, col):
492			"""Return whether the table has a column with the given name or index
493			"""
494			return self.table.HasColumn(col)
495
496	bh	818	def NumRows(self):
497			return self.table.NumRows()
498	bh	765
499	bh	818	def NumColumns(self):
500			return self.table.NumColumns()
501	bh	765
502	bh	818	def ReadRowAsDict(self, record):
503	bh	765	"""Return the record no. record as a dict mapping field names to values
504			"""
505			if self.t_table is not None:
506	bh	839	return self.t_table.ReadRowAsDict(record)
507	bh	765	else:
508	bh	818	return self.table.ReadRowAsDict(record)
509	bh	765
510	bh	849	def ReadValue(self, row, col):
511			"""Return the value of the specified row and column
512
513			The col parameter may be the index of the column or its name.
514			"""
515			if self.t_table is not None:
516			return self.t_table.ReadValue(row, col)
517			else:
518			return self.table.ReadValue(row, col)
519
520	bh	765	def copy_to_transient(self):
521			"""Internal: Create a transient table and copy the data into it"""
522			self.t_table = TransientTable(self.transient_db, self)
523
524			def transient_table(self):
525			"""
526			Return a table whose underlying implementation is in the transient db
527			"""
528			if self.t_table is None:
529			self.copy_to_transient()
530			return self.t_table
531
532	bh	818	def ValueRange(self, col):
533	bh	765	if self.t_table is None:
534			self.copy_to_transient()
535	bh	839	return self.t_table.ValueRange(col)
536	bh	765
537	bh	839	def UniqueValues(self, col):
538	bh	765	if self.t_table is None:
539			self.copy_to_transient()
540	bh	839	return self.t_table.UniqueValues(col)
541	bh	844
542			def SimpleQuery(self, left, comparison, right):
543			if self.t_table is None:
544			self.copy_to_transient()
545			# Make sure to use the column object of the transient table. The
546			# left argument is always a column object so we can just ask the
547			# t_table for the right object.
548	jonathan	933	if hasattr(right, "name"):
549			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
550			comparison,
551			self.t_table.Column(right.name))
552			else:
553			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
554			comparison, right)
555	bh	984
556			def Dependencies(self):
557			"""Return a tuple containing the original table"""
558			return (self.table,)
559	frank	1026
560	bh	1043	def Width(self, col):
561			return self.table.Width(col)
Name	Value
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svn:keywords	Author Date Id Revision