Thuban/Model/transientdb.py

# Copyright (C) 2003 by Intevation GmbH
# Authors:
# Bernhard Herzog <[email protected]>
#
# This program is free software under the GPL (>=v2)
# Read the file COPYING coming with the software for details.

"""Database for transient data

This database is intended for data representations needed during the
lifetime of a Thuban session but which is not permanent. Examples of
this are for instance a join of two DBF files where the DBF files are
the permanent representation of the data and the join only exists in the
Thuban session and is reconstructed when the session is opened.
"""

__version__ = "$Revision$"
# $Source$
# $Id$

import os
import weakref
from sqlite import connect

from base import TitledObject

import table

sql_type_map = {
    table.FIELDTYPE_INT: "INTEGER",
    table.FIELDTYPE_STRING: "VARCHAR",
    table.FIELDTYPE_DOUBLE: "FLOAT",
    }

type_converter_map = {
    table.FIELDTYPE_INT: int,
    table.FIELDTYPE_STRING: str,
    table.FIELDTYPE_DOUBLE: float,
    }

class TransientDatabase:

    def __init__(self, filename):
        self.filename = filename
        self.conn = connect(filename)
        # Counters to produce unique table and column names
        self.num_tables = 0
        self.num_cols = 0
        # Since there's only once process using the SQLite database, we
        # might be able to get a tad more speed with default_synchronous
        # OFF. So far I haven't seen any measurable speedup, though.
        #self.execute("PRAGMA default_synchronous = OFF")

    def __del__(self):
        self.close()

    def close(self):
        if self.conn is not None:
            self.conn.close()
            self.conn = None

    def new_table_name(self):
        self.num_tables += 1
        return "Table%03d" % self.num_tables

    def new_column_name(self):
        self.num_cols += 1
        return "Col%03d" % self.num_cols

    def execute(self, *args):
        """execute the SQL statement in the database and return the result"""
        cursor = self.conn.cursor()
        cursor.execute(*args)
        result = cursor.fetchone()
        self.conn.commit()
        return result

    def cursor(self):
        return self.conn.cursor()


class ColumnReference:

    def __init__(self, name, type, internal_name):
        self.name = name
        self.type = type
        self.internal_name = internal_name


class TransientTableBase(table.OldTableInterfaceMixin):

    """Base class for tables in the transient database"""

    def __init__(self, transient_db):
        """Initialize the table for use with the given transient db"""
        self.db = transient_db
        self.tablename = self.db.new_table_name()
        self.indexed_columns = {}
        self.read_record_cursor = None
        self.read_record_last_row = None
        self.read_record_last_result = None

    def create(self, columns):
        self.columns = columns
        self.name_to_column = {}
        self.orig_names = []
        self.internal_to_orig = {}
        self.orig_to_internal = {}
        self.column_map = {}

        # Create the column objects and fill various maps and lists
        for index in range(len(self.columns)):
            col = self.columns[index]
            self.name_to_column[col.name] = col
            self.orig_names.append(col.name)
            self.internal_to_orig[col.internal_name] = col.name
            self.orig_to_internal[col.name] = col.internal_name
            self.column_map[col.name] = col
            self.column_map[index] = col

        # Build the CREATE TABLE statement and create the table in the
        # database
        table_types = ["id INTEGER PRIMARY KEY"]
        for col in self.columns:
            table_types.append("%s %s" % (col.internal_name,
                                          sql_type_map[col.type]))
        table_stmt = "CREATE TABLE %s (\n    %s\n);" % (self.tablename,
                                                   ",\n    ".join(table_types))
        self.db.execute(table_stmt)

    def transient_table(self):
        """
        Return a table whose underlying implementation is in the transient db
        """
        return self

    def ensure_index(self, column):
        """Ensure that there's an index on the given column"""
        if not column in self.indexed_columns:
            internal_name = self.orig_to_internal[column]
            indexname = "Index_%s_%s" % (self.tablename, internal_name)
            stmt = "CREATE INDEX %s ON %s (%s);" % (indexname, self.tablename,
                                                    internal_name)
            self.db.execute(stmt)
            self.indexed_columns[column] = 1

    def NumColumns(self):
        return len(self.columns)

    def NumRows(self):
        result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
        return int(result[0])

    def Columns(self):
        return self.columns

    def Column(self, col):
        return self.column_map[col]

    def HasColumn(self, col):
        """Return whether the table has a column with the given name or index
        """
        return self.column_map.has_key(col)

    def ReadRowAsDict(self, index):
        # Implementation Strategy: Executing a completely new select
        # statement every time this method is called is too slow. The
        # most important usage is to read the records more or less
        # sequentially. This happens e.g. when drawing a layer with a
        # classification where the shapes are drawn in order of the
        # shape ids. Another pattern is that the same row is requested
        # several times in a row. This happens in the table view, for
        # instance.

        # We can exploit this to make access faster by having one cursor
        # open all the time and keeping the last row read around in case
        # the same row is accessed again the next time and if the row
        # index is larger than the row we have read last we simply fetch
        # rows from the cursor until we've reached the requested row. If
        # the requested row index is smaller then we start a new cursor.

        # FIXME: So far this scheme seems to work well enough. Obvious
        # improvements would be to start the cursor at exactly the
        # requested row (should be efficient and easy to do now that the
        # id is the primary key) and to perhaps to also start a new
        # cursor if the requested index is much larger than the last row
        # so that we don't read and discard lots of the rows.

        # Check whether we have to start a new cursor
        if self.read_record_cursor is None or index <self.read_record_last_row:
            stmt = ("SELECT %s FROM %s;"
                    % (", ".join([c.internal_name for c in self.columns]),
                       self.tablename))
            self.read_record_cursor = self.db.cursor()
            self.read_record_cursor.execute(stmt)
            self.read_record_last_row = -1
            self.read_record_last_result = None

        # Now we should have a cursor at a position less than or equal
        # to the index so the following if statement will always set
        # result to a suitable value
        assert index >= self.read_record_last_row

        if index == self.read_record_last_row:
            result = self.read_record_last_result
        else:
            for i in range(index - self.read_record_last_row):
                result = self.read_record_cursor.fetchone()
                self.read_record_last_result = result
        self.read_record_last_row = index
        return dict(zip(self.orig_names, result))

    def ReadValue(self, row, col):
        """Return the value of the specified row and column

        The col parameter may be the index of the column or its name.
        """
        # Depending on the actual access patterns of the table data, it
        # might be a bit faster in some circumstances to not implement
        # this via ReadRowAsDict, but this simple implementation should
        # be fast enough for most purposes.
        return self.ReadRowAsDict(row)[self.column_map[col].name]

    def ValueRange(self, col):
        col = self.column_map[col]
        iname = col.internal_name
        min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"
                                   % (iname, iname, self.tablename))
        converter = type_converter_map[col.type]
        return (converter(min), converter(max))

    def UniqueValues(self, col):
        iname = self.column_map[col].internal_name
        cursor = self.db.cursor()
        cursor.execute("SELECT %s FROM %s GROUP BY %s;"
                       % (iname, self.tablename, iname))
        result = []
        while 1:
            row = cursor.fetchone()
            if row is None:
                break
            result.append(row[0])
        return result

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

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

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

        return max

    def Precision(self, col):
        """Return the precision of the column

        The return value is the maximum number of numeric characters after the
        decimal if column type is double. Else precision zero is returned.
        The column can be represented by index or name.
        """
    
        type  = self.column_map[col].type
        if type == sql_type_map[table.FIELDTYPE_DOUBLE]:
            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 0
            
            max = 0
            for value in values:
                if value is None: continue
                l = len(str(value % 1))
                if l > max:
                    max = l
            if max > 2:
                return max - 2
            else:
                return 0
        else:
            return 0

    def SimpleQuery(self, left, comparison, right):
        """Return the indices of all rows that matching a condition.

        Parameters:
           left -- The column object for the left side of the comparison

           comparison -- The comparison operator as a string. It must be
                         one of '==', '!=', '<', '<=', '>=', '>'

           right -- The right hand side of the comparison. It must be
                    either a column object or a value, i.e. a string,
                    int or float.

        The return value is a sorted list of the indices of the rows
        where the condition is true.
        """
        if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
            raise ValueError("Comparison operator %r not allowed" % comparison)

        if hasattr(right, "internal_name"):
            right_template = right.internal_name
            params = ()
        else:
            right_template = "%s"
            params = (right,)

        query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
                % (self.tablename, left.internal_name, comparison,
                   right_template)

        cursor = self.db.cursor()
        cursor.execute(query, params)
        result = []
        while 1:
            row = cursor.fetchone()
            if row is None:
                break
            result.append(row[0])
        return result

    def Dependencies(self):
        """Placeholder for a method in a derived class.

        Return a sequence with the tables and other data objects that
        self depends on.
        """
        raise NotImplementedError


class TransientTable(TitledObject, TransientTableBase):

    """A Table in a transient DB that starts as the copy of a Thuban Table."""

    def __init__(self, transient_db, table):
        """Create a new table in the given transient DB as a copy of table

        The table argument can be any object implementing the Table
        interface.
        """
        TransientTableBase.__init__(self, transient_db)
        TitledObject.__init__(self, table.Title())
        self.create(table)

    def create(self, table):
        columns = []
        for col in table.Columns():
            columns.append(ColumnReference(col.name, col.type,
                                           self.db.new_column_name()))
        TransientTableBase.create(self, columns)

        # copy the input table to the transient db

        # A key to insert to use for the formatting of the insert
        # statement. The key must not be equal to any of the column
        # names so we construct one by building a string of x's that is
        # longer than any of the column names
        id_key = max([len(col.name) for col in self.columns]) * "x"

        insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
                               % (self.tablename,
                                  ", ".join([col.internal_name
                                             for col in self.columns]),
                                  id_key,
                                  ", ".join(["%%(%s)s" % col.name
                                             for col in self.columns]))
        cursor = self.db.cursor()
        for i in range(table.NumRows()):
            row = table.ReadRowAsDict(i)
            row[id_key] = i
            cursor.execute(insert_template, row)
        self.db.conn.commit()


class TransientJoinedTable(TitledObject, TransientTableBase):

    """A Table in the transient DB that contains a join of two tables"""

    def __init__(self, transient_db, left_table, left_field,
                 right_table, right_field = None, outer_join = False):
        """Create a new table in the transient DB as a join of two tables.

        Both input tables, left_table and right_table must have a
        transient_table method that returns a table object for a table
        in the transient database. The join is performed on the condition
        that the value of the left_field column the the left table is
        equal to the value of the right_field in the right_table.

        The joined table contains all columns of the input tables with
        one exception: Any column in the right_table with the same name
        as one of the columns in the left_table will be omitted. This is
        somewhat of an implementation detail, but is done so that the
        column names of the joined table can be the same as the column
        names of the input tables without having to create prefixes.
        """
        TransientTableBase.__init__(self, transient_db)
        self.dependencies = (left_table, right_table)
        self.left_table = left_table.transient_table()
        self.left_field = left_field
        self.right_table = right_table.transient_table()
        if right_field:
            self.right_field = right_field
        else:
            self.right_field = self.left_field
        self.outer_join = outer_join

        title = "Join of %(left)s and %(right)s" \
                % {"left": self.left_table.Title(),
                   "right": self.right_table.Title()}
        TitledObject.__init__(self, title)

        self.create()

    def create(self):
        """Internal: Create the table with the joined data"""
        self.tablename = self.db.new_table_name()

        self.right_table.ensure_index(self.right_field)

        # Coalesce the column information
        visited = {}
        columns = []
        for col in self.left_table.columns + self.right_table.columns:
            if col.name in visited:
                # We can't allow multiple columns with the same original
                # name, so omit this one. FIXME: There should be a
                # better solution.
                continue
            columns.append(col)
        TransientTableBase.create(self, columns)

        # Copy the joined data to the table.
        internal_names = [col.internal_name for col in self.columns]
        if self.outer_join:
            join_operator = 'LEFT OUTER JOIN'
        else:
            join_operator = 'JOIN'
        stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
                " %s %s ON %s = %s;"
                % (self.tablename,
                   ", ".join(internal_names),
                   self.left_table.tablename,
                   ", ".join(internal_names),
                   self.left_table.tablename,
                   join_operator,
                   self.right_table.tablename,
                   self.orig_to_internal[self.left_field],
                   self.orig_to_internal[self.right_field]))
        self.db.execute(stmt)

    def Dependencies(self):
        """Return a tuple with the two tables the join depends on."""
        return self.dependencies


class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):

    """Table that copies data to a transient table on demand.

    The AutoTransientTable takes another table as input and copies data
    to a table in a TransientDatabase instance on demand.
    """

    def __init__(self, transient_db, table):
        TitledObject.__init__(self, table.Title())
        self.transient_db = transient_db
        self.table = table
        self.t_table = None

    def Columns(self):
        return self.table.Columns()

    def Column(self, col):
        return self.table.Column(col)

    def HasColumn(self, col):
        """Return whether the table has a column with the given name or index
        """
        return self.table.HasColumn(col)

    def NumRows(self):
        return self.table.NumRows()

    def NumColumns(self):
        return self.table.NumColumns()

    def ReadRowAsDict(self, record):
        """Return the record no. record as a dict mapping field names to values
        """
        if self.t_table is not None:
            return self.t_table.ReadRowAsDict(record)
        else:
            return self.table.ReadRowAsDict(record)

    def ReadValue(self, row, col):
        """Return the value of the specified row and column

        The col parameter may be the index of the column or its name.
        """
        if self.t_table is not None:
            return self.t_table.ReadValue(row, col)
        else:
            return self.table.ReadValue(row, col)

    def copy_to_transient(self):
        """Internal: Create a transient table and copy the data into it"""
        self.t_table = TransientTable(self.transient_db, self)

    def transient_table(self):
        """
        Return a table whose underlying implementation is in the transient db
        """
        if self.t_table is None:
            self.copy_to_transient()
        return self.t_table

    def ValueRange(self, col):
        if self.t_table is None:
            self.copy_to_transient()
        return self.t_table.ValueRange(col)

    def UniqueValues(self, col):
        if self.t_table is None:
            self.copy_to_transient()
        return self.t_table.UniqueValues(col)

    def SimpleQuery(self, left, comparison, right):
        if self.t_table is None:
            self.copy_to_transient()
        # Make sure to use the column object of the transient table. The
        # left argument is always a column object so we can just ask the
        # t_table for the right object.
        if hasattr(right, "name"):
            return self.t_table.SimpleQuery(self.t_table.Column(left.name),
                                            comparison, 
                                            self.t_table.Column(right.name))
        else:
            return self.t_table.SimpleQuery(self.t_table.Column(left.name),
                                            comparison, right)

    def Dependencies(self):
        """Return a tuple containing the original table"""
        return (self.table,)

1	bh	765	# Copyright (C) 2003 by Intevation GmbH
2			# Authors:
3			# Bernhard Herzog <[email protected]>
4			#
5			# This program is free software under the GPL (>=v2)
6			# Read the file COPYING coming with the software for details.
7
8			"""Database for transient data
9
10			This database is intended for data representations needed during the
11			lifetime of a Thuban session but which is not permanent. Examples of
12			this are for instance a join of two DBF files where the DBF files are
13			the permanent representation of the data and the join only exists in the
14			Thuban session and is reconstructed when the session is opened.
15			"""
16
17			__version__ = "$Revision$"
18			# $Source$
19			# $Id$
20
21			import os
22			import weakref
23			from sqlite import connect
24
25	jan	1020	from base import TitledObject
26
27	bh	765	import table
28
29			sql_type_map = {
30			table.FIELDTYPE_INT: "INTEGER",
31			table.FIELDTYPE_STRING: "VARCHAR",
32			table.FIELDTYPE_DOUBLE: "FLOAT",
33			}
34
35			type_converter_map = {
36			table.FIELDTYPE_INT: int,
37			table.FIELDTYPE_STRING: str,
38			table.FIELDTYPE_DOUBLE: float,
39			}
40
41			class TransientDatabase:
42
43			def __init__(self, filename):
44			self.filename = filename
45			self.conn = connect(filename)
46			# Counters to produce unique table and column names
47			self.num_tables = 0
48			self.num_cols = 0
49			# Since there's only once process using the SQLite database, we
50			# might be able to get a tad more speed with default_synchronous
51			# OFF. So far I haven't seen any measurable speedup, though.
52			#self.execute("PRAGMA default_synchronous = OFF")
53
54			def __del__(self):
55			self.close()
56
57			def close(self):
58	bh	777	if self.conn is not None:
59	bh	765	self.conn.close()
60	bh	777	self.conn = None
61	bh	765
62			def new_table_name(self):
63			self.num_tables += 1
64			return "Table%03d" % self.num_tables
65
66			def new_column_name(self):
67			self.num_cols += 1
68			return "Col%03d" % self.num_cols
69
70			def execute(self, *args):
71			"""execute the SQL statement in the database and return the result"""
72			cursor = self.conn.cursor()
73			cursor.execute(*args)
74			result = cursor.fetchone()
75			self.conn.commit()
76			return result
77
78			def cursor(self):
79			return self.conn.cursor()
80
81
82			class ColumnReference:
83
84			def __init__(self, name, type, internal_name):
85			self.name = name
86			self.type = type
87			self.internal_name = internal_name
88
89
90	bh	818	class TransientTableBase(table.OldTableInterfaceMixin):
91	bh	765
92			"""Base class for tables in the transient database"""
93
94			def __init__(self, transient_db):
95			"""Initialize the table for use with the given transient db"""
96			self.db = transient_db
97			self.tablename = self.db.new_table_name()
98			self.indexed_columns = {}
99			self.read_record_cursor = None
100			self.read_record_last_row = None
101	bh	785	self.read_record_last_result = None
102	bh	765
103			def create(self, columns):
104			self.columns = columns
105			self.name_to_column = {}
106			self.orig_names = []
107			self.internal_to_orig = {}
108			self.orig_to_internal = {}
109	bh	818	self.column_map = {}
110	bh	765
111			# Create the column objects and fill various maps and lists
112	bh	818	for index in range(len(self.columns)):
113			col = self.columns[index]
114	bh	765	self.name_to_column[col.name] = col
115			self.orig_names.append(col.name)
116			self.internal_to_orig[col.internal_name] = col.name
117			self.orig_to_internal[col.name] = col.internal_name
118	bh	818	self.column_map[col.name] = col
119			self.column_map[index] = col
120	bh	765
121			# Build the CREATE TABLE statement and create the table in the
122			# database
123	bh	841	table_types = ["id INTEGER PRIMARY KEY"]
124	bh	765	for col in self.columns:
125			table_types.append("%s %s" % (col.internal_name,
126			sql_type_map[col.type]))
127			table_stmt = "CREATE TABLE %s (\n %s\n);" % (self.tablename,
128			",\n ".join(table_types))
129			self.db.execute(table_stmt)
130
131			def transient_table(self):
132			"""
133			Return a table whose underlying implementation is in the transient db
134			"""
135			return self
136
137			def ensure_index(self, column):
138			"""Ensure that there's an index on the given column"""
139			if not column in self.indexed_columns:
140			internal_name = self.orig_to_internal[column]
141			indexname = "Index_%s_%s" % (self.tablename, internal_name)
142			stmt = "CREATE INDEX %s ON %s (%s);" % (indexname, self.tablename,
143			internal_name)
144			self.db.execute(stmt)
145			self.indexed_columns[column] = 1
146
147	bh	818	def NumColumns(self):
148	bh	765	return len(self.columns)
149
150	bh	818	def NumRows(self):
151	bh	765	result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
152			return int(result[0])
153
154	bh	818	def Columns(self):
155			return self.columns
156
157			def Column(self, col):
158			return self.column_map[col]
159
160	bh	839	def HasColumn(self, col):
161			"""Return whether the table has a column with the given name or index
162			"""
163			return self.column_map.has_key(col)
164
165	bh	818	def ReadRowAsDict(self, index):
166	bh	849	# Implementation Strategy: Executing a completely new select
167			# statement every time this method is called is too slow. The
168			# most important usage is to read the records more or less
169			# sequentially. This happens e.g. when drawing a layer with a
170			# classification where the shapes are drawn in order of the
171			# shape ids. Another pattern is that the same row is requested
172			# several times in a row. This happens in the table view, for
173			# instance.
174
175			# We can exploit this to make access faster by having one cursor
176			# open all the time and keeping the last row read around in case
177			# the same row is accessed again the next time and if the row
178			# index is larger than the row we have read last we simply fetch
179			# rows from the cursor until we've reached the requested row. If
180			# the requested row index is smaller then we start a new cursor.
181
182			# FIXME: So far this scheme seems to work well enough. Obvious
183			# improvements would be to start the cursor at exactly the
184			# requested row (should be efficient and easy to do now that the
185			# id is the primary key) and to perhaps to also start a new
186			# cursor if the requested index is much larger than the last row
187			# so that we don't read and discard lots of the rows.
188
189			# Check whether we have to start a new cursor
190	bh	765	if self.read_record_cursor is None or index <self.read_record_last_row:
191			stmt = ("SELECT %s FROM %s;"
192			% (", ".join([c.internal_name for c in self.columns]),
193			self.tablename))
194			self.read_record_cursor = self.db.cursor()
195			self.read_record_cursor.execute(stmt)
196			self.read_record_last_row = -1
197	bh	785	self.read_record_last_result = None
198
199			# Now we should have a cursor at a position less than or equal
200			# to the index so the following if statement will always set
201			# result to a suitable value
202			assert index >= self.read_record_last_row
203
204			if index == self.read_record_last_row:
205	bh	818	result = self.read_record_last_result
206	bh	785	else:
207			for i in range(index - self.read_record_last_row):
208			result = self.read_record_cursor.fetchone()
209			self.read_record_last_result = result
210	bh	765	self.read_record_last_row = index
211	bh	785	return dict(zip(self.orig_names, result))
212	bh	765
213	bh	849	def ReadValue(self, row, col):
214			"""Return the value of the specified row and column
215
216			The col parameter may be the index of the column or its name.
217			"""
218			# Depending on the actual access patterns of the table data, it
219			# might be a bit faster in some circumstances to not implement
220			# this via ReadRowAsDict, but this simple implementation should
221			# be fast enough for most purposes.
222			return self.ReadRowAsDict(row)[self.column_map[col].name]
223
224	bh	818	def ValueRange(self, col):
225			col = self.column_map[col]
226	bh	765	iname = col.internal_name
227			min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"
228			% (iname, iname, self.tablename))
229			converter = type_converter_map[col.type]
230	bh	818	return (converter(min), converter(max))
231	bh	765
232	bh	818	def UniqueValues(self, col):
233			iname = self.column_map[col].internal_name
234	bh	765	cursor = self.db.cursor()
235			cursor.execute("SELECT %s FROM %s GROUP BY %s;"
236			% (iname, self.tablename, iname))
237			result = []
238			while 1:
239			row = cursor.fetchone()
240			if row is None:
241			break
242			result.append(row[0])
243			return result
244
245	frank	1026	def Width(self, col):
246			"""Return the maximum width of values in the column
247
248			The return value is the the maximum length of string representation
249			of the values in the column (represented by index or name)."""
250			max = 0
251
252			type = self.column_map[col].type
253			iname = self.column_map[col].internal_name
254			cursor = self.db.cursor()
255			cursor.execute("SELECT %s FROM %s;" % (iname, self.tablename))
256			values = [ i[0] for i in cursor.fetchall()]
257			if not values:
258			return None
259
260			if type == sql_type_map[table.FIELDTYPE_DOUBLE]:
261			prec = self.Precision(col)
262			format = "%%.%df" % prec
263			elif type == sql_type_map[table.FIELDTYPE_INT]:
264			format = "%d"
265			else:
266			format = "%s"
267			for value in values:
268			if value is None: continue
269			l = len(format % value)
270			if l > max:
271			max = l
272
273			return max
274
275			def Precision(self, col):
276			"""Return the precision of the column
277
278			The return value is the maximum number of numeric characters after the
279			decimal if column type is double. Else precision zero is returned.
280			The column can be represented by index or name.
281			"""
282
283			type = self.column_map[col].type
284			if type == sql_type_map[table.FIELDTYPE_DOUBLE]:
285			iname = self.column_map[col].internal_name
286			cursor = self.db.cursor()
287			cursor.execute("SELECT %s FROM %s;" % (iname, self.tablename))
288			values = [ i[0] for i in cursor.fetchall()]
289			if not values:
290			return 0
291
292			max = 0
293			for value in values:
294			if value is None: continue
295			l = len(str(value % 1))
296			if l > max:
297			max = l
298			if max > 2:
299			return max - 2
300			else:
301			return 0
302			else:
303			return 0
304
305	bh	841	def SimpleQuery(self, left, comparison, right):
306			"""Return the indices of all rows that matching a condition.
307	bh	765
308	bh	841	Parameters:
309			left -- The column object for the left side of the comparison
310
311			comparison -- The comparison operator as a string. It must be
312			one of '==', '!=', '<', '<=', '>=', '>'
313
314			right -- The right hand side of the comparison. It must be
315			either a column object or a value, i.e. a string,
316			int or float.
317
318			The return value is a sorted list of the indices of the rows
319			where the condition is true.
320			"""
321			if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
322			raise ValueError("Comparison operator %r not allowed" % comparison)
323
324			if hasattr(right, "internal_name"):
325			right_template = right.internal_name
326			params = ()
327			else:
328			right_template = "%s"
329			params = (right,)
330
331			query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
332			% (self.tablename, left.internal_name, comparison,
333			right_template)
334
335			cursor = self.db.cursor()
336			cursor.execute(query, params)
337			result = []
338			while 1:
339			row = cursor.fetchone()
340			if row is None:
341			break
342			result.append(row[0])
343			return result
344
345	bh	984	def Dependencies(self):
346			"""Placeholder for a method in a derived class.
347	bh	841
348	bh	984	Return a sequence with the tables and other data objects that
349			self depends on.
350			"""
351			raise NotImplementedError
352
353
354	jan	1020	class TransientTable(TitledObject, TransientTableBase):
355	bh	765
356			"""A Table in a transient DB that starts as the copy of a Thuban Table."""
357
358			def __init__(self, transient_db, table):
359			"""Create a new table in the given transient DB as a copy of table
360
361			The table argument can be any object implementing the Table
362			interface.
363			"""
364			TransientTableBase.__init__(self, transient_db)
365	jan	1020	TitledObject.__init__(self, table.Title())
366	bh	765	self.create(table)
367
368			def create(self, table):
369			columns = []
370	bh	818	for col in table.Columns():
371			columns.append(ColumnReference(col.name, col.type,
372	bh	765	self.db.new_column_name()))
373			TransientTableBase.create(self, columns)
374
375			# copy the input table to the transient db
376	bh	841
377			# A key to insert to use for the formatting of the insert
378			# statement. The key must not be equal to any of the column
379			# names so we construct one by building a string of x's that is
380			# longer than any of the column names
381			id_key = max([len(col.name) for col in self.columns]) * "x"
382
383			insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
384	bh	765	% (self.tablename,
385			", ".join([col.internal_name
386			for col in self.columns]),
387	bh	841	id_key,
388	bh	765	", ".join(["%%(%s)s" % col.name
389			for col in self.columns]))
390			cursor = self.db.cursor()
391	bh	818	for i in range(table.NumRows()):
392	bh	841	row = table.ReadRowAsDict(i)
393			row[id_key] = i
394			cursor.execute(insert_template, row)
395	bh	765	self.db.conn.commit()
396
397
398
399	jan	1020	class TransientJoinedTable(TitledObject, TransientTableBase):
400	bh	765
401			"""A Table in the transient DB that contains a join of two tables"""
402
403			def __init__(self, transient_db, left_table, left_field,
404	frank	1009	right_table, right_field = None, outer_join = False):
405	bh	765	"""Create a new table in the transient DB as a join of two tables.
406
407			Both input tables, left_table and right_table must have a
408			transient_table method that returns a table object for a table
409	frank	1002	in the transient database. The join is performed on the condition
410	bh	765	that the value of the left_field column the the left table is
411			equal to the value of the right_field in the right_table.
412
413			The joined table contains all columns of the input tables with
414			one exception: Any column in the right_table with the same name
415			as one of the columns in the left_table will be omitted. This is
416			somewhat of an implementation detail, but is done so that the
417			column names of the joined table can be the same as the column
418			names of the input tables without having to create prefixes.
419			"""
420			TransientTableBase.__init__(self, transient_db)
421	bh	984	self.dependencies = (left_table, right_table)
422	bh	765	self.left_table = left_table.transient_table()
423			self.left_field = left_field
424			self.right_table = right_table.transient_table()
425			if right_field:
426			self.right_field = right_field
427			else:
428			self.right_field = self.left_field
429	frank	1009	self.outer_join = outer_join
430	jan	1020
431			title = "Join of %(left)s and %(right)s" \
432			% {"left": self.left_table.Title(),
433			"right": self.right_table.Title()}
434			TitledObject.__init__(self, title)
435
436	bh	765	self.create()
437
438			def create(self):
439			"""Internal: Create the table with the joined data"""
440			self.tablename = self.db.new_table_name()
441
442			self.right_table.ensure_index(self.right_field)
443
444			# Coalesce the column information
445			visited = {}
446			columns = []
447			for col in self.left_table.columns + self.right_table.columns:
448			if col.name in visited:
449	bh	841	# We can't allow multiple columns with the same original
450			# name, so omit this one. FIXME: There should be a
451			# better solution.
452	bh	765	continue
453			columns.append(col)
454			TransientTableBase.create(self, columns)
455
456			# Copy the joined data to the table.
457			internal_names = [col.internal_name for col in self.columns]
458	frank	1009	if self.outer_join:
459			join_operator = 'LEFT OUTER JOIN'
460			else:
461			join_operator = 'JOIN'
462	bh	841	stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
463	frank	1009	" %s %s ON %s = %s;"
464	bh	841	% (self.tablename,
465			", ".join(internal_names),
466			self.left_table.tablename,
467			", ".join(internal_names),
468			self.left_table.tablename,
469	frank	1009	join_operator,
470	bh	841	self.right_table.tablename,
471			self.orig_to_internal[self.left_field],
472			self.orig_to_internal[self.right_field]))
473	bh	765	self.db.execute(stmt)
474
475	bh	984	def Dependencies(self):
476			"""Return a tuple with the two tables the join depends on."""
477			return self.dependencies
478	bh	765
479	bh	984
480	jan	1020	class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
481	bh	765
482			"""Table that copies data to a transient table on demand.
483
484			The AutoTransientTable takes another table as input and copies data
485			to a table in a TransientDatabase instance on demand.
486			"""
487
488			def __init__(self, transient_db, table):
489	jan	1020	TitledObject.__init__(self, table.Title())
490	bh	765	self.transient_db = transient_db
491			self.table = table
492			self.t_table = None
493
494	bh	818	def Columns(self):
495			return self.table.Columns()
496	bh	765
497	bh	818	def Column(self, col):
498			return self.table.Column(col)
499	bh	765
500	bh	839	def HasColumn(self, col):
501			"""Return whether the table has a column with the given name or index
502			"""
503			return self.table.HasColumn(col)
504
505	bh	818	def NumRows(self):
506			return self.table.NumRows()
507	bh	765
508	bh	818	def NumColumns(self):
509			return self.table.NumColumns()
510	bh	765
511	bh	818	def ReadRowAsDict(self, record):
512	bh	765	"""Return the record no. record as a dict mapping field names to values
513			"""
514			if self.t_table is not None:
515	bh	839	return self.t_table.ReadRowAsDict(record)
516	bh	765	else:
517	bh	818	return self.table.ReadRowAsDict(record)
518	bh	765
519	bh	849	def ReadValue(self, row, col):
520			"""Return the value of the specified row and column
521
522			The col parameter may be the index of the column or its name.
523			"""
524			if self.t_table is not None:
525			return self.t_table.ReadValue(row, col)
526			else:
527			return self.table.ReadValue(row, col)
528
529	bh	765	def copy_to_transient(self):
530			"""Internal: Create a transient table and copy the data into it"""
531			self.t_table = TransientTable(self.transient_db, self)
532
533			def transient_table(self):
534			"""
535			Return a table whose underlying implementation is in the transient db
536			"""
537			if self.t_table is None:
538			self.copy_to_transient()
539			return self.t_table
540
541	bh	818	def ValueRange(self, col):
542	bh	765	if self.t_table is None:
543			self.copy_to_transient()
544	bh	839	return self.t_table.ValueRange(col)
545	bh	765
546	bh	839	def UniqueValues(self, col):
547	bh	765	if self.t_table is None:
548			self.copy_to_transient()
549	bh	839	return self.t_table.UniqueValues(col)
550	bh	844
551			def SimpleQuery(self, left, comparison, right):
552			if self.t_table is None:
553			self.copy_to_transient()
554			# Make sure to use the column object of the transient table. The
555			# left argument is always a column object so we can just ask the
556			# t_table for the right object.
557	jonathan	933	if hasattr(right, "name"):
558			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
559			comparison,
560			self.t_table.Column(right.name))
561			else:
562			return self.t_table.SimpleQuery(self.t_table.Column(left.name),
563			comparison, right)
564	bh	984
565			def Dependencies(self):
566			"""Return a tuple containing the original table"""
567			return (self.table,)
568	frank	1026
Name	Value
svn:eol-style	native
svn:keywords	Author Date Id Revision