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	# 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	from base import TitledObject
24
25	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	if self.conn is not None:
57	self.conn.close()
58	self.conn = None
59
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	class TransientTableBase(table.OldTableInterfaceMixin):
89
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	self.read_record_last_result = None
100
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	self.column_map = {}
108
109	# Create the column objects and fill various maps and lists
110	for index in range(len(self.columns)):
111	col = self.columns[index]
112	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	self.column_map[col.name] = col
117	self.column_map[index] = col
118
119	# Build the CREATE TABLE statement and create the table in the
120	# database
121	table_types = ["id INTEGER PRIMARY KEY"]
122	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	def NumColumns(self):
146	return len(self.columns)
147
148	def NumRows(self):
149	result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
150	return int(result[0])
151
152	def Columns(self):
153	return self.columns
154
155	def Column(self, col):
156	return self.column_map[col]
157
158	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	def ReadRowAsDict(self, index):
164	# 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	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	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	result = self.read_record_last_result
204	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	self.read_record_last_row = index
209	return dict(zip(self.orig_names, result))
210
211	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	def ValueRange(self, col):
223	col = self.column_map[col]
224	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	return (converter(min), converter(max))
229
230	def UniqueValues(self, col):
231	iname = self.column_map[col].internal_name
232	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	def Width(self, col):
244	"""Return the maximum width of values in the column
245
246	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	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 == table.FIELDTYPE_DOUBLE:
261	format = "%.12f"
262	elif type == 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	def SimpleQuery(self, left, comparison, right):
275	"""Return the indices of all rows that matching a condition.
276
277	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	def Dependencies(self):
315	"""Placeholder for a method in a derived class.
316
317	Return a sequence with the tables and other data objects that
318	self depends on.
319	"""
320	raise NotImplementedError
321
322
323	class TransientTable(TitledObject, TransientTableBase):
324
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	TitledObject.__init__(self, table.Title())
335	self.create(table)
336
337	def create(self, table):
338	columns = []
339	for col in table.Columns():
340	columns.append(ColumnReference(col.name, col.type,
341	self.db.new_column_name()))
342	TransientTableBase.create(self, columns)
343
344	# copy the input table to the transient db
345
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	% (self.tablename,
354	", ".join([col.internal_name
355	for col in self.columns]),
356	id_key,
357	", ".join(["%%(%s)s" % col.name
358	for col in self.columns]))
359	cursor = self.db.cursor()
360	for i in range(table.NumRows()):
361	row = table.ReadRowAsDict(i)
362	row[id_key] = i
363	cursor.execute(insert_template, row)
364	self.db.conn.commit()
365
366
367
368	class TransientJoinedTable(TitledObject, TransientTableBase):
369
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	right_table, right_field = None, outer_join = False):
374	"""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	in the transient database. The join is performed on the condition
379	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,
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	"""
388	TransientTableBase.__init__(self, transient_db)
389	self.dependencies = (left_table, right_table)
390	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	self.outer_join = outer_join
398
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	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	# 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	internal_right_col =self.right_table.orig_to_internal[self.right_field]
418
419	# Coalesce the column information
420	visited = {}
421	columns = []
422	newcolumns = []
423	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	TransientTableBase.create(self, newcolumns)
438
439	# Copy the joined data to the table.
440	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	if self.outer_join:
444	join_operator = 'LEFT OUTER JOIN'
445	else:
446	join_operator = 'JOIN'
447	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
448	" %s %s ON %s.%s = %s.%s;"
449	% (self.tablename,
450	", ".join(newinternal_names),
451	self.left_table.tablename,
452	", ".join(internal_references),
453	self.left_table.tablename,
454	join_operator,
455	self.right_table.tablename,
456	self.left_table.tablename,
457	internal_left_col,
458	self.right_table.tablename,
459	internal_right_col))
460	self.db.execute(stmt)
461
462	def Dependencies(self):
463	"""Return a tuple with the two tables the join depends on."""
464	return self.dependencies
465
466	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
473
474	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
475
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	TitledObject.__init__(self, table.Title())
484	self.transient_db = transient_db
485	self.table = table
486	self.t_table = None
487
488	def Columns(self):
489	return self.table.Columns()
490
491	def Column(self, col):
492	return self.table.Column(col)
493
494	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	def NumRows(self):
500	return self.table.NumRows()
501
502	def NumColumns(self):
503	return self.table.NumColumns()
504
505	def ReadRowAsDict(self, record):
506	"""Return the record no. record as a dict mapping field names to values
507	"""
508	if self.t_table is not None:
509	return self.t_table.ReadRowAsDict(record)
510	else:
511	return self.table.ReadRowAsDict(record)
512
513	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	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	def ValueRange(self, col):
536	if self.t_table is None:
537	self.copy_to_transient()
538	return self.t_table.ValueRange(col)
539
540	def UniqueValues(self, col):
541	if self.t_table is None:
542	self.copy_to_transient()
543	return self.t_table.UniqueValues(col)
544
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	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
559	def Dependencies(self):
560	"""Return a tuple containing the original table"""
561	return (self.table,)
562
563	def Width(self, col):
564	return self.table.Width(col)
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