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__ = "$Revision$"
# $Source$
# $Id$

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			from sqlite import connect
22
23	jan	1020	from base import TitledObject
24
25	bh	765	import table
26
27			sql_type_map = {
28			table.FIELDTYPE_INT: "INTEGER",
29			table.FIELDTYPE_STRING: "VARCHAR",
30			table.FIELDTYPE_DOUBLE: "FLOAT",
31			}
32
33			type_converter_map = {
34			table.FIELDTYPE_INT: int,
35			table.FIELDTYPE_STRING: str,
36			table.FIELDTYPE_DOUBLE: float,
37			}
38
39			class TransientDatabase:
40
41			def __init__(self, filename):
42			self.filename = filename
43			self.conn = connect(filename)
44			# Counters to produce unique table and column names
45			self.num_tables = 0
46			self.num_cols = 0
47			# Since there's only once process using the SQLite database, we
48			# might be able to get a tad more speed with default_synchronous
49			# OFF. So far I haven't seen any measurable speedup, though.
50			#self.execute("PRAGMA default_synchronous = OFF")
51
52			def __del__(self):
53			self.close()
54
55			def close(self):
56	bh	777	if self.conn is not None:
57	bh	765	self.conn.close()
58	bh	777	self.conn = None
59	bh	765
60			def new_table_name(self):
61			self.num_tables += 1
62			return "Table%03d" % self.num_tables
63
64			def new_column_name(self):
65			self.num_cols += 1
66			return "Col%03d" % self.num_cols
67
68			def execute(self, *args):
69			"""execute the SQL statement in the database and return the result"""
70			cursor = self.conn.cursor()
71			cursor.execute(*args)
72			result = cursor.fetchone()
73			self.conn.commit()
74			return result
75
76			def cursor(self):
77			return self.conn.cursor()
78
79
80			class ColumnReference:
81
82			def __init__(self, name, type, internal_name):
83			self.name = name
84			self.type = type
85			self.internal_name = internal_name
86
87
88	bh	818	class TransientTableBase(table.OldTableInterfaceMixin):
89	bh	765
90			"""Base class for tables in the transient database"""
91
92			def __init__(self, transient_db):
93			"""Initialize the table for use with the given transient db"""
94			self.db = transient_db
95			self.tablename = self.db.new_table_name()
96			self.indexed_columns = {}
97			self.read_record_cursor = None
98			self.read_record_last_row = None
99	bh	785	self.read_record_last_result = None
100	bh	765
101			def create(self, columns):
102			self.columns = columns
103			self.name_to_column = {}
104			self.orig_names = []
105			self.internal_to_orig = {}
106			self.orig_to_internal = {}
107	bh	818	self.column_map = {}
108	bh	765
109			# Create the column objects and fill various maps and lists
110	bh	818	for index in range(len(self.columns)):
111			col = self.columns[index]
112	bh	765	self.name_to_column[col.name] = col
113			self.orig_names.append(col.name)
114			self.internal_to_orig[col.internal_name] = col.name
115			self.orig_to_internal[col.name] = col.internal_name
116	bh	818	self.column_map[col.name] = col
117			self.column_map[index] = col
118	bh	765
119			# Build the CREATE TABLE statement and create the table in the
120			# database
121	bh	841	table_types = ["id INTEGER PRIMARY KEY"]
122	bh	765	for col in self.columns:
123			table_types.append("%s %s" % (col.internal_name,
124			sql_type_map[col.type]))
125			table_stmt = "CREATE TABLE %s (\n %s\n);" % (self.tablename,
126			",\n ".join(table_types))
127			self.db.execute(table_stmt)
128
129			def transient_table(self):
130			"""
131			Return a table whose underlying implementation is in the transient db
132			"""
133			return self
134
135			def ensure_index(self, column):
136			"""Ensure that there's an index on the given column"""
137			if not column in self.indexed_columns:
138			internal_name = self.orig_to_internal[column]
139			indexname = "Index_%s_%s" % (self.tablename, internal_name)
140			stmt = "CREATE INDEX %s ON %s (%s);" % (indexname, self.tablename,
141			internal_name)
142			self.db.execute(stmt)
143			self.indexed_columns[column] = 1
144
145	bh	818	def NumColumns(self):
146	bh	765	return len(self.columns)
147
148	bh	818	def NumRows(self):
149	bh	765	result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
150			return int(result[0])
151
152	bh	818	def Columns(self):
153			return self.columns
154
155			def Column(self, col):
156			return self.column_map[col]
157
158	bh	839	def HasColumn(self, col):
159			"""Return whether the table has a column with the given name or index
160			"""
161			return self.column_map.has_key(col)
162
163	bh	818	def ReadRowAsDict(self, index):
164	bh	849	# Implementation Strategy: Executing a completely new select
165			# statement every time this method is called is too slow. The
166			# most important usage is to read the records more or less
167			# sequentially. This happens e.g. when drawing a layer with a
168			# classification where the shapes are drawn in order of the
169			# shape ids. Another pattern is that the same row is requested
170			# several times in a row. This happens in the table view, for
171			# instance.
172
173			# We can exploit this to make access faster by having one cursor
174			# open all the time and keeping the last row read around in case
175			# the same row is accessed again the next time and if the row
176			# index is larger than the row we have read last we simply fetch
177			# rows from the cursor until we've reached the requested row. If
178			# the requested row index is smaller then we start a new cursor.
179
180			# FIXME: So far this scheme seems to work well enough. Obvious
181			# improvements would be to start the cursor at exactly the
182			# requested row (should be efficient and easy to do now that the
183			# id is the primary key) and to perhaps to also start a new
184			# cursor if the requested index is much larger than the last row
185			# so that we don't read and discard lots of the rows.
186
187			# Check whether we have to start a new cursor
188	bh	765	if self.read_record_cursor is None or index <self.read_record_last_row:
189			stmt = ("SELECT %s FROM %s;"
190			% (", ".join([c.internal_name for c in self.columns]),
191			self.tablename))
192			self.read_record_cursor = self.db.cursor()
193			self.read_record_cursor.execute(stmt)
194			self.read_record_last_row = -1
195	bh	785	self.read_record_last_result = None
196
197			# Now we should have a cursor at a position less than or equal
198			# to the index so the following if statement will always set
199			# result to a suitable value
200			assert index >= self.read_record_last_row
201
202			if index == self.read_record_last_row:
203	bh	818	result = self.read_record_last_result
204	bh	785	else:
205			for i in range(index - self.read_record_last_row):
206			result = self.read_record_cursor.fetchone()
207			self.read_record_last_result = result
208	bh	765	self.read_record_last_row = index
209	bh	785	return dict(zip(self.orig_names, result))
210	bh	765
211	bh	849	def ReadValue(self, row, col):
212			"""Return the value of the specified row and column
213
214			The col parameter may be the index of the column or its name.
215			"""
216			# Depending on the actual access patterns of the table data, it
217			# might be a bit faster in some circumstances to not implement
218			# this via ReadRowAsDict, but this simple implementation should
219			# be fast enough for most purposes.
220			return self.ReadRowAsDict(row)[self.column_map[col].name]
221
222	bh	818	def ValueRange(self, col):
223			col = self.column_map[col]
224	bh	765	iname = col.internal_name
225			min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"
226			% (iname, iname, self.tablename))
227			converter = type_converter_map[col.type]
228	bh	818	return (converter(min), converter(max))
229	bh	765
230	bh	818	def UniqueValues(self, col):
231			iname = self.column_map[col].internal_name
232	bh	765	cursor = self.db.cursor()
233			cursor.execute("SELECT %s FROM %s GROUP BY %s;"
234			% (iname, self.tablename, iname))
235			result = []
236			while 1:
237			row = cursor.fetchone()
238			if row is None:
239			break
240			result.append(row[0])
241			return result
242
243	frank	1026	def Width(self, col):
244			"""Return the maximum width of values in the column
245
246	bh	1381	The return value is the the maximum length of string
247			representation of the values in the column (represented by index
248			or name).
249			"""
250	frank	1026	max = 0
251	bh	1381
252	frank	1026	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	bh	1381	if type == table.FIELDTYPE_DOUBLE:
261	bh	1043	format = "%.12f"
262	bh	1381	elif type == table.FIELDTYPE_INT:
263	frank	1026	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	bh	1364	The joined table contains all columns of the input tables,
383			however, the column names of the right table may be changed
384			slightly to make them unique in the joined table. This is
385			currently done by appending a sufficient number of underscores
386			('_').
387	bh	765	"""
388			TransientTableBase.__init__(self, transient_db)
389	bh	984	self.dependencies = (left_table, right_table)
390	bh	765	self.left_table = left_table.transient_table()
391			self.left_field = left_field
392			self.right_table = right_table.transient_table()
393			if right_field:
394			self.right_field = right_field
395			else:
396			self.right_field = self.left_field
397	frank	1009	self.outer_join = outer_join
398	jan	1020
399			title = "Join of %(left)s and %(right)s" \
400			% {"left": self.left_table.Title(),
401			"right": self.right_table.Title()}
402			TitledObject.__init__(self, title)
403
404	bh	765	self.create()
405
406			def create(self):
407			"""Internal: Create the table with the joined data"""
408			self.tablename = self.db.new_table_name()
409
410			self.right_table.ensure_index(self.right_field)
411
412	bh	1328	# determine the internal column names to join on before
413			# coalescing the column information because if the external
414			# column names are the same they will be mapped to the same
415			# internal name afterwards.
416			internal_left_col = self.left_table.orig_to_internal[self.left_field]
417	bh	1364	internal_right_col =self.right_table.orig_to_internal[self.right_field]
418	bh	1328
419	bh	765	# Coalesce the column information
420			visited = {}
421			columns = []
422	frank	1333	newcolumns = []
423	bh	1364	for table in (self.left_table, self.right_table):
424			for col in table.Columns():
425			colname = col.name
426			# We can't allow multiple columns with the same
427			# original name, so append '_' to this one until
428			# it is unique.
429			# FIXME: There should be a better solution.
430			while colname in visited:
431			colname = colname + '_'
432			columns.append((table.tablename, col))
433			newcol = ColumnReference(colname, col.type,
434			"Col%03d" % (len(newcolumns)+1))
435			newcolumns.append(newcol)
436			visited[colname] = 1
437	frank	1333	TransientTableBase.create(self, newcolumns)
438	bh	765
439			# Copy the joined data to the table.
440	frank	1333	newinternal_names = [col.internal_name for col in self.columns]
441			internal_references = ["%s.%s" % (table, col.internal_name)
442			for table, col in columns]
443	frank	1009	if self.outer_join:
444			join_operator = 'LEFT OUTER JOIN'
445			else:
446			join_operator = 'JOIN'
447	bh	841	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
448	frank	1333	" %s %s ON %s.%s = %s.%s;"
449	bh	841	% (self.tablename,
450	frank	1333	", ".join(newinternal_names),
451	bh	841	self.left_table.tablename,
452	frank	1333	", ".join(internal_references),
453	bh	841	self.left_table.tablename,
454	frank	1009	join_operator,
455	bh	841	self.right_table.tablename,
456	frank	1333	self.left_table.tablename,
457	bh	1328	internal_left_col,
458	frank	1333	self.right_table.tablename,
459	bh	1328	internal_right_col))
460	bh	765	self.db.execute(stmt)
461
462	bh	984	def Dependencies(self):
463			"""Return a tuple with the two tables the join depends on."""
464			return self.dependencies
465	bh	765
466	bh	1375	def JoinType(self):
467			"""Return the type of the join (either 'INNER' or 'LEFT OUTER')"""
468			if self.outer_join:
469			return "LEFT OUTER"
470			else:
471			return "INNER"
472	bh	984
473	bh	1375
474	jan	1020	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
475	bh	765
476			"""Table that copies data to a transient table on demand.
477
478			The AutoTransientTable takes another table as input and copies data
479			to a table in a TransientDatabase instance on demand.
480			"""
481
482			def __init__(self, transient_db, table):
483	jan	1020	TitledObject.__init__(self, table.Title())
484	bh	765	self.transient_db = transient_db
485			self.table = table
486			self.t_table = None
487
488	bh	818	def Columns(self):
489			return self.table.Columns()
490	bh	765
491	bh	818	def Column(self, col):
492			return self.table.Column(col)
493	bh	765
494	bh	839	def HasColumn(self, col):
495			"""Return whether the table has a column with the given name or index
496			"""
497			return self.table.HasColumn(col)
498
499	bh	818	def NumRows(self):
500			return self.table.NumRows()
501	bh	765
502	bh	818	def NumColumns(self):
503			return self.table.NumColumns()
504	bh	765
505	bh	818	def ReadRowAsDict(self, record):
506	bh	765	"""Return the record no. record as a dict mapping field names to values
507			"""
508			if self.t_table is not None:
509	bh	839	return self.t_table.ReadRowAsDict(record)
510	bh	765	else:
511	bh	818	return self.table.ReadRowAsDict(record)
512	bh	765
513	bh	849	def ReadValue(self, row, col):
514			"""Return the value of the specified row and column
515
516			The col parameter may be the index of the column or its name.
517			"""
518			if self.t_table is not None:
519			return self.t_table.ReadValue(row, col)
520			else:
521			return self.table.ReadValue(row, col)
522
523	bh	765	def copy_to_transient(self):
524			"""Internal: Create a transient table and copy the data into it"""
525			self.t_table = TransientTable(self.transient_db, self)
526
527			def transient_table(self):
528			"""
529			Return a table whose underlying implementation is in the transient db
530			"""
531			if self.t_table is None:
532			self.copy_to_transient()
533			return self.t_table
534
535	bh	818	def ValueRange(self, col):
536	bh	765	if self.t_table is None:
537			self.copy_to_transient()
538	bh	839	return self.t_table.ValueRange(col)
539	bh	765
540	bh	839	def UniqueValues(self, col):
541	bh	765	if self.t_table is None:
542			self.copy_to_transient()
543	bh	839	return self.t_table.UniqueValues(col)
544	bh	844
545			def SimpleQuery(self, left, comparison, right):
546			if self.t_table is None:
547			self.copy_to_transient()
548			# Make sure to use the column object of the transient table. The
549			# left argument is always a column object so we can just ask the
550			# t_table for the right object.
551	jonathan	933	if hasattr(right, "name"):
552			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
553			comparison,
554			self.t_table.Column(right.name))
555			else:
556			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
557			comparison, right)
558	bh	984
559			def Dependencies(self):
560			"""Return a tuple containing the original table"""
561			return (self.table,)
562	frank	1026
563	bh	1043	def Width(self, col):
564			return self.table.Width(col)
Name	Value
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svn:keywords	Author Date Id Revision