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 == table.FIELDTYPE_DOUBLE:
            format = "%.12f"
        elif type == 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,
        however, the column names of the right table may be changed
        slightly to make them unique in the joined table. This is
        currently done by appending a sufficient number of underscores
        ('_').
        """
        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 in (self.left_table, self.right_table):
            for col in table.Columns():
                colname = col.name
                # 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 colname in visited:
                    colname = colname + '_'
                columns.append((table.tablename, col))
                newcol = ColumnReference(colname, col.type,
                                            "Col%03d" % (len(newcolumns)+1))
                newcolumns.append(newcol)
                visited[colname] = 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

    def JoinType(self):
        """Return the type of the join (either 'INNER' or 'LEFT OUTER')"""
        if self.outer_join:
            return "LEFT OUTER"
        else:
            return "INNER"


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	bh	1381	The return value is the the maximum length of string
249			representation of the values in the column (represented by index
250			or name).
251			"""
252	frank	1026	max = 0
253	bh	1381
254	frank	1026	type = self.column_map[col].type
255			iname = self.column_map[col].internal_name
256			cursor = self.db.cursor()
257			cursor.execute("SELECT %s FROM %s;" % (iname, self.tablename))
258			values = [ i[0] for i in cursor.fetchall()]
259			if not values:
260			return None
261
262	bh	1381	if type == table.FIELDTYPE_DOUBLE:
263	bh	1043	format = "%.12f"
264	bh	1381	elif type == table.FIELDTYPE_INT:
265	frank	1026	format = "%d"
266			else:
267			format = "%s"
268			for value in values:
269			if value is None: continue
270			l = len(format % value)
271			if l > max:
272			max = l
273
274			return max
275
276	bh	841	def SimpleQuery(self, left, comparison, right):
277			"""Return the indices of all rows that matching a condition.
278	bh	765
279	bh	841	Parameters:
280			left -- The column object for the left side of the comparison
281
282			comparison -- The comparison operator as a string. It must be
283			one of '==', '!=', '<', '<=', '>=', '>'
284
285			right -- The right hand side of the comparison. It must be
286			either a column object or a value, i.e. a string,
287			int or float.
288
289			The return value is a sorted list of the indices of the rows
290			where the condition is true.
291			"""
292			if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
293			raise ValueError("Comparison operator %r not allowed" % comparison)
294
295			if hasattr(right, "internal_name"):
296			right_template = right.internal_name
297			params = ()
298			else:
299			right_template = "%s"
300			params = (right,)
301
302			query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
303			% (self.tablename, left.internal_name, comparison,
304			right_template)
305
306			cursor = self.db.cursor()
307			cursor.execute(query, params)
308			result = []
309			while 1:
310			row = cursor.fetchone()
311			if row is None:
312			break
313			result.append(row[0])
314			return result
315
316	bh	984	def Dependencies(self):
317			"""Placeholder for a method in a derived class.
318	bh	841
319	bh	984	Return a sequence with the tables and other data objects that
320			self depends on.
321			"""
322			raise NotImplementedError
323
324
325	jan	1020	class TransientTable(TitledObject, TransientTableBase):
326	bh	765
327			"""A Table in a transient DB that starts as the copy of a Thuban Table."""
328
329			def __init__(self, transient_db, table):
330			"""Create a new table in the given transient DB as a copy of table
331
332			The table argument can be any object implementing the Table
333			interface.
334			"""
335			TransientTableBase.__init__(self, transient_db)
336	jan	1020	TitledObject.__init__(self, table.Title())
337	bh	765	self.create(table)
338
339			def create(self, table):
340			columns = []
341	bh	818	for col in table.Columns():
342			columns.append(ColumnReference(col.name, col.type,
343	bh	765	self.db.new_column_name()))
344			TransientTableBase.create(self, columns)
345
346			# copy the input table to the transient db
347	bh	841
348			# A key to insert to use for the formatting of the insert
349			# statement. The key must not be equal to any of the column
350			# names so we construct one by building a string of x's that is
351			# longer than any of the column names
352			id_key = max([len(col.name) for col in self.columns]) * "x"
353
354			insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
355	bh	765	% (self.tablename,
356			", ".join([col.internal_name
357			for col in self.columns]),
358	bh	841	id_key,
359	bh	765	", ".join(["%%(%s)s" % col.name
360			for col in self.columns]))
361			cursor = self.db.cursor()
362	bh	818	for i in range(table.NumRows()):
363	bh	841	row = table.ReadRowAsDict(i)
364			row[id_key] = i
365			cursor.execute(insert_template, row)
366	bh	765	self.db.conn.commit()
367
368
369
370	jan	1020	class TransientJoinedTable(TitledObject, TransientTableBase):
371	bh	765
372			"""A Table in the transient DB that contains a join of two tables"""
373
374			def __init__(self, transient_db, left_table, left_field,
375	frank	1009	right_table, right_field = None, outer_join = False):
376	bh	765	"""Create a new table in the transient DB as a join of two tables.
377
378			Both input tables, left_table and right_table must have a
379			transient_table method that returns a table object for a table
380	frank	1002	in the transient database. The join is performed on the condition
381	bh	765	that the value of the left_field column the the left table is
382			equal to the value of the right_field in the right_table.
383
384	bh	1364	The joined table contains all columns of the input tables,
385			however, the column names of the right table may be changed
386			slightly to make them unique in the joined table. This is
387			currently done by appending a sufficient number of underscores
388			('_').
389	bh	765	"""
390			TransientTableBase.__init__(self, transient_db)
391	bh	984	self.dependencies = (left_table, right_table)
392	bh	765	self.left_table = left_table.transient_table()
393			self.left_field = left_field
394			self.right_table = right_table.transient_table()
395			if right_field:
396			self.right_field = right_field
397			else:
398			self.right_field = self.left_field
399	frank	1009	self.outer_join = outer_join
400	jan	1020
401			title = "Join of %(left)s and %(right)s" \
402			% {"left": self.left_table.Title(),
403			"right": self.right_table.Title()}
404			TitledObject.__init__(self, title)
405
406	bh	765	self.create()
407
408			def create(self):
409			"""Internal: Create the table with the joined data"""
410			self.tablename = self.db.new_table_name()
411
412			self.right_table.ensure_index(self.right_field)
413
414	bh	1328	# determine the internal column names to join on before
415			# coalescing the column information because if the external
416			# column names are the same they will be mapped to the same
417			# internal name afterwards.
418			internal_left_col = self.left_table.orig_to_internal[self.left_field]
419	bh	1364	internal_right_col =self.right_table.orig_to_internal[self.right_field]
420	bh	1328
421	bh	765	# Coalesce the column information
422			visited = {}
423			columns = []
424	frank	1333	newcolumns = []
425	bh	1364	for table in (self.left_table, self.right_table):
426			for col in table.Columns():
427			colname = col.name
428			# We can't allow multiple columns with the same
429			# original name, so append '_' to this one until
430			# it is unique.
431			# FIXME: There should be a better solution.
432			while colname in visited:
433			colname = colname + '_'
434			columns.append((table.tablename, col))
435			newcol = ColumnReference(colname, col.type,
436			"Col%03d" % (len(newcolumns)+1))
437			newcolumns.append(newcol)
438			visited[colname] = 1
439	frank	1333	TransientTableBase.create(self, newcolumns)
440	bh	765
441			# Copy the joined data to the table.
442	frank	1333	newinternal_names = [col.internal_name for col in self.columns]
443			internal_references = ["%s.%s" % (table, col.internal_name)
444			for table, col in columns]
445	frank	1009	if self.outer_join:
446			join_operator = 'LEFT OUTER JOIN'
447			else:
448			join_operator = 'JOIN'
449	bh	841	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
450	frank	1333	" %s %s ON %s.%s = %s.%s;"
451	bh	841	% (self.tablename,
452	frank	1333	", ".join(newinternal_names),
453	bh	841	self.left_table.tablename,
454	frank	1333	", ".join(internal_references),
455	bh	841	self.left_table.tablename,
456	frank	1009	join_operator,
457	bh	841	self.right_table.tablename,
458	frank	1333	self.left_table.tablename,
459	bh	1328	internal_left_col,
460	frank	1333	self.right_table.tablename,
461	bh	1328	internal_right_col))
462	bh	765	self.db.execute(stmt)
463
464	bh	984	def Dependencies(self):
465			"""Return a tuple with the two tables the join depends on."""
466			return self.dependencies
467	bh	765
468	bh	1375	def JoinType(self):
469			"""Return the type of the join (either 'INNER' or 'LEFT OUTER')"""
470			if self.outer_join:
471			return "LEFT OUTER"
472			else:
473			return "INNER"
474	bh	984
475	bh	1375
476	jan	1020	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
477	bh	765
478			"""Table that copies data to a transient table on demand.
479
480			The AutoTransientTable takes another table as input and copies data
481			to a table in a TransientDatabase instance on demand.
482			"""
483
484			def __init__(self, transient_db, table):
485	jan	1020	TitledObject.__init__(self, table.Title())
486	bh	765	self.transient_db = transient_db
487			self.table = table
488			self.t_table = None
489
490	bh	818	def Columns(self):
491			return self.table.Columns()
492	bh	765
493	bh	818	def Column(self, col):
494			return self.table.Column(col)
495	bh	765
496	bh	839	def HasColumn(self, col):
497			"""Return whether the table has a column with the given name or index
498			"""
499			return self.table.HasColumn(col)
500
501	bh	818	def NumRows(self):
502			return self.table.NumRows()
503	bh	765
504	bh	818	def NumColumns(self):
505			return self.table.NumColumns()
506	bh	765
507	bh	818	def ReadRowAsDict(self, record):
508	bh	765	"""Return the record no. record as a dict mapping field names to values
509			"""
510			if self.t_table is not None:
511	bh	839	return self.t_table.ReadRowAsDict(record)
512	bh	765	else:
513	bh	818	return self.table.ReadRowAsDict(record)
514	bh	765
515	bh	849	def ReadValue(self, row, col):
516			"""Return the value of the specified row and column
517
518			The col parameter may be the index of the column or its name.
519			"""
520			if self.t_table is not None:
521			return self.t_table.ReadValue(row, col)
522			else:
523			return self.table.ReadValue(row, col)
524
525	bh	765	def copy_to_transient(self):
526			"""Internal: Create a transient table and copy the data into it"""
527			self.t_table = TransientTable(self.transient_db, self)
528
529			def transient_table(self):
530			"""
531			Return a table whose underlying implementation is in the transient db
532			"""
533			if self.t_table is None:
534			self.copy_to_transient()
535			return self.t_table
536
537	bh	818	def ValueRange(self, col):
538	bh	765	if self.t_table is None:
539			self.copy_to_transient()
540	bh	839	return self.t_table.ValueRange(col)
541	bh	765
542	bh	839	def UniqueValues(self, col):
543	bh	765	if self.t_table is None:
544			self.copy_to_transient()
545	bh	839	return self.t_table.UniqueValues(col)
546	bh	844
547			def SimpleQuery(self, left, comparison, right):
548			if self.t_table is None:
549			self.copy_to_transient()
550			# Make sure to use the column object of the transient table. The
551			# left argument is always a column object so we can just ask the
552			# t_table for the right object.
553	jonathan	933	if hasattr(right, "name"):
554			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
555			comparison,
556			self.t_table.Column(right.name))
557			else:
558			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
559			comparison, right)
560	bh	984
561			def Dependencies(self):
562			"""Return a tuple containing the original table"""
563			return (self.table,)
564	frank	1026
565	bh	1043	def Width(self, col):
566			return self.table.Width(col)
Name	Value
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svn:keywords	Author Date Id Revision