"""
A type of parameter that represents a filter on one or more
columns of a database table.
+ Special features provide support for negation, upper and lower bounds,
+ as well as sorting and clipping.
- field should be a dictionary of field names and types, e.g.
-
- {'node_id': Parameter(int, "Node identifier"),
- 'hostname': Parameter(int, "Fully qualified hostname", max = 255),
- ...}
+ fields should be a dictionary of field names and types
Only filters on non-sequence type fields are supported.
+ example : fields = {'node_id': Parameter(int, "Node identifier"),
+ 'hostname': Parameter(int, "Fully qualified hostname", max = 255),
+ ...}
+
filter should be a dictionary of field names and values
- representing an intersection (if join_with is AND) or union (if
- join_with is OR) filter. If a value is a sequence type, then it
- should represent a list of possible values for that field.
+ representing the criteria for filtering.
+ example : filter = { 'hostname' : '*.edu' , site_id : [34,54] }
+ Whether the filter represents an intersection (AND) or a union (OR)
+ of these criteria is determined by the join_with argument
+ provided to the sql method below
+
+ Special features:
- Special forms:
* a field starting with the ~ character means negation.
- example : { '~peer_id' : None }
+ example : filter = { '~peer_id' : None }
+
* a field starting with < [ ] or > means lower than or greater than
< > uses strict comparison
[ ] is for using <= or >= instead
- example : { '>time' : 1178531418 }
- example : { ']event_id' : 2305 }
- * a field starting with [ or ] means older than or more recent than
- the associated value should be a given unix timestamp
+ example : filter = { ']event_id' : 2305 }
+ example : filter = { '>time' : 1178531418 }
+ in this example the integer value denotes a unix timestamp
+
+ * if a value is a sequence type, then it should represent
+ a list of possible values for that field
+ example : filter = { 'node_id' : [12,34,56] }
+
* a (string) value containing either a * or a % character is
treated as a (sql) pattern; * are replaced with % that is the
SQL wildcard character.
- example : { 'hostname' : '*.jp' }
+ example : filter = { 'hostname' : '*.jp' }
+
+ * fields starting with - are special and relate to row selection, i.e. sorting and clipping
+ * '-SORT' : a field name, or an ordered list of field names that are used for sorting
+ * these fields may start with + (default) or - for denoting increasing or decreasing order
+ example : filter = { '-SORT' : [ '+node_id', '-hostname' ] }
+ * '-OFFSET' : the number of first rows to be ommitted
+ * '-LIMIT' : the amount of rows to be returned
+ example : filter = { '-OFFSET' : 100, '-PAGE':25}
+
+ A realistic example would read
+ GetNodes ( { 'hostname' : '*.edu' , '-SORT' : 'hostname' , '-OFFSET' : 30 , '-PAGE' : 25 } )
+ and that would return nodes matching '*.edu' in alphabetical order from 31th to 55th
"""
def __init__(self, fields = {}, filter = {}, doc = "Attribute filter"):
else:
assert join_with in ("AND", "OR")
+ # init
+ sorts = []
+ clips = []
+
for field, value in self.iteritems():
# handle negation, numeric comparisons
# simple, 1-depth only mechanism
modifiers={'~' : False,
'<' : False, '>' : False,
'[' : False, ']' : False,
+ '-' : False,
}
for char in modifiers.keys():
field = field[1:]
break
- if field not in self.fields:
-# print 'current fields',self.fields
- raise PLCInvalidArgument, "Invalid filter field '%s'" % field
-
- if isinstance(value, (list, tuple, set)):
- # Turn empty list into (NULL) instead of invalid ()
- if not value:
- value = [None]
-
- operator = "IN"
- value = map(str, map(api.db.quote, value))
- value = "(%s)" % ", ".join(value)
+ # filter on fields
+ if not modifiers['-']:
+ if field not in self.fields:
+ raise PLCInvalidArgument, "Invalid filter field '%s'" % field
+
+ if isinstance(value, (list, tuple, set)):
+ # Turn empty list into (NULL) instead of invalid ()
+ if not value:
+ value = [None]
+
+ operator = "IN"
+ value = map(str, map(api.db.quote, value))
+ value = "(%s)" % ", ".join(value)
+ else:
+ if value is None:
+ operator = "IS"
+ value = "NULL"
+ elif isinstance(value, StringTypes) and \
+ (value.find("*") > -1 or value.find("%") > -1):
+ operator = "LIKE"
+ value = str(api.db.quote(value.replace("*", "%")))
+ else:
+ operator = "="
+ if modifiers['<']:
+ operator='<'
+ if modifiers['>']:
+ operator='>'
+ if modifiers['[']:
+ operator='<='
+ if modifiers[']']:
+ operator='>='
+ else:
+ value = str(api.db.quote(value))
+
+ clause = "%s %s %s" % (field, operator, value)
+
+ if modifiers['~']:
+ clause = " ( NOT %s ) " % (clause)
+
+ conditionals.append(clause)
+ # sorting and clipping
else:
- if value is None:
- operator = "IS"
- value = "NULL"
- elif isinstance(value, StringTypes) and \
- (value.find("*") > -1 or value.find("%") > -1):
- operator = "LIKE"
- value = str(api.db.quote(value.replace("*", "%")))
- else:
- operator = "="
- if modifiers['<']:
- operator='<'
- if modifiers['>']:
- operator='>'
- if modifiers['[']:
- operator='<='
- if modifiers[']']:
- operator='>='
- else:
- value = str(api.db.quote(value))
-
- clause = "%s %s %s" % (field, operator, value)
-
- if modifiers['~']:
- clause = " ( NOT %s ) " % (clause)
-
- conditionals.append(clause)
-
-# print 'sql=',(" %s " % join_with).join(conditionals)
- return (" %s " % join_with).join(conditionals)
+ if field not in ('SORT','OFFSET','LIMIT'):
+ raise PLCInvalidArgument, "Invalid filter, unknown sort and clip field %r"%field
+ # sorting
+ if field == 'SORT':
+ if not isinstance(value,(list,tuple,set)):
+ value=[value]
+ for field in value:
+ order = 'ASC'
+ if field[0] == '+':
+ field = field[1:]
+ elif field[0] == '-':
+ field = field[1:]
+ order = 'DESC'
+ if field not in self.fields:
+ raise PLCInvalidArgument, "Invalid field %r in SORT filter"%field
+ sorts.append("%s %s"%(field,order))
+ # clipping
+ elif field == 'OFFSET':
+ clips.append("OFFSET %d"%value)
+ # clipping continued
+ elif field == 'LIMIT' :
+ clips.append("LIMIT %d"%value)
+
+ where_part = (" %s " % join_with).join(conditionals)
+ clip_part = ""
+ if sorts:
+ clip_part += " ORDER BY " + ",".join(sorts)
+ if clips:
+ clip_part += " " + " ".join(clips)
+# print 'where_part=',where_part,'clip_part',clip_part
+ return (where_part,clip_part)
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