/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/transientdb.py
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revision 765 by bh, Tue Apr 29 12:42:14 2003 UTC revision 1020 by jan, Fri May 23 13:03:07 2003 UTC
# Line 22  import os Line 22  import os
22  import weakref  import weakref
23  from sqlite import connect  from sqlite import connect
24    
25    from base import TitledObject
26    
27  import table  import table
28    
29  sql_type_map = {  sql_type_map = {
# Line 53  class TransientDatabase: Line 55  class TransientDatabase:
55          self.close()          self.close()
56    
57      def close(self):      def close(self):
58          if self.conn:          if self.conn is not None:
59              self.conn.close()              self.conn.close()
60                self.conn = None
61    
62      def new_table_name(self):      def new_table_name(self):
63          self.num_tables += 1          self.num_tables += 1
# Line 84  class ColumnReference: Line 87  class ColumnReference:
87          self.internal_name = internal_name          self.internal_name = internal_name
88    
89    
90  class TransientTableBase:  class TransientTableBase(table.OldTableInterfaceMixin):
91    
92      """Base class for tables in the transient database"""      """Base class for tables in the transient database"""
93    
# Line 95  class TransientTableBase: Line 98  class TransientTableBase:
98          self.indexed_columns = {}          self.indexed_columns = {}
99          self.read_record_cursor = None          self.read_record_cursor = None
100          self.read_record_last_row = None          self.read_record_last_row = None
101            self.read_record_last_result = None
102    
103      def create(self, columns):      def create(self, columns):
104          self.columns = columns          self.columns = columns
# Line 102  class TransientTableBase: Line 106  class TransientTableBase:
106          self.orig_names = []          self.orig_names = []
107          self.internal_to_orig = {}          self.internal_to_orig = {}
108          self.orig_to_internal = {}          self.orig_to_internal = {}
109            self.column_map = {}
110    
111          # Create the column objects and fill various maps and lists          # Create the column objects and fill various maps and lists
112          for col in self.columns:          for index in range(len(self.columns)):
113                col = self.columns[index]
114              self.name_to_column[col.name] = col              self.name_to_column[col.name] = col
115              self.orig_names.append(col.name)              self.orig_names.append(col.name)
116              self.internal_to_orig[col.internal_name] = col.name              self.internal_to_orig[col.internal_name] = col.name
117              self.orig_to_internal[col.name] = col.internal_name              self.orig_to_internal[col.name] = col.internal_name
118                self.column_map[col.name] = col
119                self.column_map[index] = col
120    
121          # Build the CREATE TABLE statement and create the table in the          # Build the CREATE TABLE statement and create the table in the
122          # database          # database
123          table_types = []          table_types = ["id INTEGER PRIMARY KEY"]
124          for col in self.columns:          for col in self.columns:
125              table_types.append("%s %s" % (col.internal_name,              table_types.append("%s %s" % (col.internal_name,
126                                            sql_type_map[col.type]))                                            sql_type_map[col.type]))
# Line 136  class TransientTableBase: Line 144  class TransientTableBase:
144              self.db.execute(stmt)              self.db.execute(stmt)
145              self.indexed_columns[column] = 1              self.indexed_columns[column] = 1
146    
147      def field_count(self):      def NumColumns(self):
148          return len(self.columns)          return len(self.columns)
149    
150      def field_info(self, i):      def NumRows(self):
         col = self.columns[i]  
         return col.type, col.name, 0, 0  
   
     def field_info_by_name(self, name):  
         for col in self.columns:  
             if col.name == name:  
                 return col.type, col.name, 0, 0  
         else:  
             return None  
   
     def record_count(self):  
151          result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)          result = self.db.execute("SELECT count(*) FROM %s;" % self.tablename)
152          return int(result[0])          return int(result[0])
153    
154      def read_record(self, index):      def Columns(self):
155            return self.columns
156    
157        def Column(self, col):
158            return self.column_map[col]
159    
160        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        def ReadRowAsDict(self, index):
166            # 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          if self.read_record_cursor is None or index <self.read_record_last_row:          if self.read_record_cursor is None or index <self.read_record_last_row:
191              stmt = ("SELECT %s FROM %s;"              stmt = ("SELECT %s FROM %s;"
192                      % (", ".join([c.internal_name for c in self.columns]),                      % (", ".join([c.internal_name for c in self.columns]),
# Line 162  class TransientTableBase: Line 194  class TransientTableBase:
194              self.read_record_cursor = self.db.cursor()              self.read_record_cursor = self.db.cursor()
195              self.read_record_cursor.execute(stmt)              self.read_record_cursor.execute(stmt)
196              self.read_record_last_row = -1              self.read_record_last_row = -1
197          for i in range(index - self.read_record_last_row):              self.read_record_last_result = None
198              result = self.read_record_cursor.fetchone()  
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                result = self.read_record_last_result
206            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          self.read_record_last_row = index          self.read_record_last_row = index
211          result = dict(zip(self.orig_names, result))          return dict(zip(self.orig_names, result))
212          return result  
213        def ReadValue(self, row, col):
214            """Return the value of the specified row and column
215    
216      def field_range(self, colname):          The col parameter may be the index of the column or its name.
217          col = self.name_to_column[colname]          """
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        def ValueRange(self, col):
225            col = self.column_map[col]
226          iname = col.internal_name          iname = col.internal_name
227          min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"          min, max = self.db.execute("SELECT min(%s), max(%s) FROM %s;"
228                                     % (iname, iname, self.tablename))                                     % (iname, iname, self.tablename))
229          converter = type_converter_map[col.type]          converter = type_converter_map[col.type]
230          return ((converter(min), None), (converter(max), None))          return (converter(min), converter(max))
231    
232      def GetUniqueValues(self, colname):      def UniqueValues(self, col):
233          iname = self.orig_to_internal[colname]          iname = self.column_map[col].internal_name
234          cursor = self.db.cursor()          cursor = self.db.cursor()
235          cursor.execute("SELECT %s FROM %s GROUP BY %s;"          cursor.execute("SELECT %s FROM %s GROUP BY %s;"
236                         % (iname, self.tablename, iname))                         % (iname, self.tablename, iname))
# Line 189  class TransientTableBase: Line 242  class TransientTableBase:
242              result.append(row[0])              result.append(row[0])
243          return result          return result
244    
245        def SimpleQuery(self, left, comparison, right):
246            """Return the indices of all rows that matching a condition.
247    
248            Parameters:
249               left -- The column object for the left side of the comparison
250    
251               comparison -- The comparison operator as a string. It must be
252                             one of '==', '!=', '<', '<=', '>=', '>'
253    
254  class TransientTable(TransientTableBase):             right -- The right hand side of the comparison. It must be
255                        either a column object or a value, i.e. a string,
256                        int or float.
257    
258            The return value is a sorted list of the indices of the rows
259            where the condition is true.
260            """
261            if comparison not in ("==", "!=", "<", "<=", ">=", ">"):
262                raise ValueError("Comparison operator %r not allowed" % comparison)
263    
264            if hasattr(right, "internal_name"):
265                right_template = right.internal_name
266                params = ()
267            else:
268                right_template = "%s"
269                params = (right,)
270    
271            query = "SELECT id FROM %s WHERE %s %s %s ORDER BY id;" \
272                    % (self.tablename, left.internal_name, comparison,
273                       right_template)
274    
275            cursor = self.db.cursor()
276            cursor.execute(query, params)
277            result = []
278            while 1:
279                row = cursor.fetchone()
280                if row is None:
281                    break
282                result.append(row[0])
283            return result
284    
285        def Dependencies(self):
286            """Placeholder for a method in a derived class.
287    
288            Return a sequence with the tables and other data objects that
289            self depends on.
290            """
291            raise NotImplementedError
292    
293    
294    class TransientTable(TitledObject, TransientTableBase):
295    
296      """A Table in a transient DB that starts as the copy of a Thuban Table."""      """A Table in a transient DB that starts as the copy of a Thuban Table."""
297    
# Line 201  class TransientTable(TransientTableBase) Line 302  class TransientTable(TransientTableBase)
302          interface.          interface.
303          """          """
304          TransientTableBase.__init__(self, transient_db)          TransientTableBase.__init__(self, transient_db)
305            TitledObject.__init__(self, table.Title())
306          self.create(table)          self.create(table)
307    
308      def create(self, table):      def create(self, table):
309          columns = []          columns = []
310          for i in range(table.field_count()):          for col in table.Columns():
311              type, name = table.field_info(i)[:2]              columns.append(ColumnReference(col.name, col.type,
             columns.append(ColumnReference(name, type,  
312                                             self.db.new_column_name()))                                             self.db.new_column_name()))
313          TransientTableBase.create(self, columns)          TransientTableBase.create(self, columns)
314    
315          # copy the input table to the transient db          # copy the input table to the transient db
316          insert_template = "INSERT INTO %s (%s) VALUES (%s);" \  
317            # A key to insert to use for the formatting of the insert
318            # statement. The key must not be equal to any of the column
319            # names so we construct one by building a string of x's that is
320            # longer than any of the column names
321            id_key = max([len(col.name) for col in self.columns]) * "x"
322    
323            insert_template = "INSERT INTO %s (id, %s) VALUES (%%(%s)s, %s);" \
324                                 % (self.tablename,                                 % (self.tablename,
325                                    ", ".join([col.internal_name                                    ", ".join([col.internal_name
326                                               for col in self.columns]),                                               for col in self.columns]),
327                                      id_key,
328                                    ", ".join(["%%(%s)s" % col.name                                    ", ".join(["%%(%s)s" % col.name
329                                               for col in self.columns]))                                               for col in self.columns]))
330          cursor = self.db.cursor()          cursor = self.db.cursor()
331          for i in range(table.record_count()):          for i in range(table.NumRows()):
332              cursor.execute(insert_template, table.read_record(i))              row = table.ReadRowAsDict(i)
333                row[id_key] = i
334                cursor.execute(insert_template, row)
335          self.db.conn.commit()          self.db.conn.commit()
336    
337    
338    
339  class TransientJoinedTable(TransientTableBase):  class TransientJoinedTable(TitledObject, TransientTableBase):
340    
341      """A Table in the transient DB that contains a join of two tables"""      """A Table in the transient DB that contains a join of two tables"""
342    
343      def __init__(self, transient_db, left_table, left_field,      def __init__(self, transient_db, left_table, left_field,
344                   right_table, right_field = None):                   right_table, right_field = None, outer_join = False):
345          """Create a new table in the transient DB as a join of two tables.          """Create a new table in the transient DB as a join of two tables.
346    
347          Both input tables, left_table and right_table must have a          Both input tables, left_table and right_table must have a
348          transient_table method that returns a table object for a table          transient_table method that returns a table object for a table
349          in the trnsient database. The join is performed on the condition          in the transient database. The join is performed on the condition
350          that the value of the left_field column the the left table is          that the value of the left_field column the the left table is
351          equal to the value of the right_field in the right_table.          equal to the value of the right_field in the right_table.
352    
# Line 247  class TransientJoinedTable(TransientTabl Line 358  class TransientJoinedTable(TransientTabl
358          names of the input tables without having to create prefixes.          names of the input tables without having to create prefixes.
359          """          """
360          TransientTableBase.__init__(self, transient_db)          TransientTableBase.__init__(self, transient_db)
361            self.dependencies = (left_table, right_table)
362          self.left_table = left_table.transient_table()          self.left_table = left_table.transient_table()
363          self.left_field = left_field          self.left_field = left_field
364          self.right_table = right_table.transient_table()          self.right_table = right_table.transient_table()
# Line 254  class TransientJoinedTable(TransientTabl Line 366  class TransientJoinedTable(TransientTabl
366              self.right_field = right_field              self.right_field = right_field
367          else:          else:
368              self.right_field = self.left_field              self.right_field = self.left_field
369            self.outer_join = outer_join
370    
371            title = "Join of %(left)s and %(right)s" \
372                    % {"left": self.left_table.Title(),
373                       "right": self.right_table.Title()}
374            TitledObject.__init__(self, title)
375    
376          self.create()          self.create()
377    
378      def create(self):      def create(self):
# Line 267  class TransientJoinedTable(TransientTabl Line 386  class TransientJoinedTable(TransientTabl
386          columns = []          columns = []
387          for col in self.left_table.columns + self.right_table.columns:          for col in self.left_table.columns + self.right_table.columns:
388              if col.name in visited:              if col.name in visited:
389                    # We can't allow multiple columns with the same original
390                    # name, so omit this one. FIXME: There should be a
391                    # better solution.
392                  continue                  continue
393              columns.append(col)              columns.append(col)
394          TransientTableBase.create(self, columns)          TransientTableBase.create(self, columns)
395    
396          # Copy the joined data to the table.          # Copy the joined data to the table.
397          internal_names = [col.internal_name for col in self.columns]          internal_names = [col.internal_name for col in self.columns]
398          stmt = "INSERT INTO %s (%s) SELECT %s FROM %s JOIN %s ON %s = %s;" \          if self.outer_join:
399                 % (self.tablename,              join_operator = 'LEFT OUTER JOIN'
400                    ", ".join(internal_names),          else:
401                    ", ".join(internal_names),              join_operator = 'JOIN'
402                    self.left_table.tablename,          stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
403                    self.right_table.tablename,                  " %s %s ON %s = %s;"
404                    self.orig_to_internal[self.left_field],                  % (self.tablename,
405                    self.orig_to_internal[self.right_field])                     ", ".join(internal_names),
406                       self.left_table.tablename,
407                       ", ".join(internal_names),
408                       self.left_table.tablename,
409                       join_operator,
410                       self.right_table.tablename,
411                       self.orig_to_internal[self.left_field],
412                       self.orig_to_internal[self.right_field]))
413          self.db.execute(stmt)          self.db.execute(stmt)
414    
415        def Dependencies(self):
416            """Return a tuple with the two tables the join depends on."""
417            return self.dependencies
418    
419    
420  class AutoTransientTable:  class AutoTransientTable(TitledObject, table.OldTableInterfaceMixin):
421    
422      """Table that copies data to a transient table on demand.      """Table that copies data to a transient table on demand.
423    
# Line 293  class AutoTransientTable: Line 426  class AutoTransientTable:
426      """      """
427    
428      def __init__(self, transient_db, table):      def __init__(self, transient_db, table):
429            TitledObject.__init__(self, table.Title())
430          self.transient_db = transient_db          self.transient_db = transient_db
431          self.table = table          self.table = table
432          self.t_table = None          self.t_table = None
433    
434      def record_count(self):      def Columns(self):
435          """Return the number of records"""          return self.table.Columns()
         return self.table.record_count()  
   
     def field_count(self):  
         """Return the number of fields in a record"""  
         return self.table.field_count()  
   
     def field_info(self, field):  
         """Return a tuple (type, name, width, prec) for the field no. field  
   
         type is the data type of the field, name the name, width the  
         field width in characters and prec the decimal precision.  
         """  
         info = self.table.field_info(field)  
         if info:  
             info = info[:2] + (0, 0)  
         return info  
   
     def field_info_by_name(self, fieldName):  
         info = self.table.field_info_by_name(fieldName)  
         if info:  
             info = info[:2] + (0, 0)  
         return info  
436    
437      def read_record(self, record):      def Column(self, col):
438            return self.table.Column(col)
439    
440        def HasColumn(self, col):
441            """Return whether the table has a column with the given name or index
442            """
443            return self.table.HasColumn(col)
444    
445        def NumRows(self):
446            return self.table.NumRows()
447    
448        def NumColumns(self):
449            return self.table.NumColumns()
450    
451        def ReadRowAsDict(self, record):
452          """Return the record no. record as a dict mapping field names to values          """Return the record no. record as a dict mapping field names to values
453          """          """
454          if self.t_table is not None:          if self.t_table is not None:
455              return self.t_table.read_record(record)              return self.t_table.ReadRowAsDict(record)
456          else:          else:
457              return self.table.read_record(record)              return self.table.ReadRowAsDict(record)
458    
459      def write_record(self, record, values):      def ReadValue(self, row, col):
460          raise NotImplementedError          """Return the value of the specified row and column
461    
462            The col parameter may be the index of the column or its name.
463            """
464            if self.t_table is not None:
465                return self.t_table.ReadValue(row, col)
466            else:
467                return self.table.ReadValue(row, col)
468    
469      def copy_to_transient(self):      def copy_to_transient(self):
470          """Internal: Create a transient table and copy the data into it"""          """Internal: Create a transient table and copy the data into it"""
# Line 345  class AutoTransientTable: Line 478  class AutoTransientTable:
478              self.copy_to_transient()              self.copy_to_transient()
479          return self.t_table          return self.t_table
480    
481      def field_range(self, colname):      def ValueRange(self, col):
482          if self.t_table is None:          if self.t_table is None:
483              self.copy_to_transient()              self.copy_to_transient()
484          return self.t_table.field_range(colname)          return self.t_table.ValueRange(col)
485    
486      def GetUniqueValues(self, colname):      def UniqueValues(self, col):
487          if self.t_table is None:          if self.t_table is None:
488              self.copy_to_transient()              self.copy_to_transient()
489          return self.t_table.GetUniqueValues(colname)          return self.t_table.UniqueValues(col)
490    
491        def SimpleQuery(self, left, comparison, right):
492            if self.t_table is None:
493                self.copy_to_transient()
494            # Make sure to use the column object of the transient table. The
495            # left argument is always a column object so we can just ask the
496            # t_table for the right object.
497            if hasattr(right, "name"):
498                return self.t_table.SimpleQuery(self.t_table.Column(left.name),
499                                                comparison,
500                                                self.t_table.Column(right.name))
501            else:
502                return self.t_table.SimpleQuery(self.t_table.Column(left.name),
503                                                comparison, right)
504    
505        def Dependencies(self):
506            """Return a tuple containing the original table"""
507            return (self.table,)
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