Iteration and update conflict with set based IOMemory store #286
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Umm, I'm now trying to figure out why Python 3 doesn't have a problem with this. |
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It probably has something to do with the API changes regarding iterators in Python 3. Methods like iteritems() and itervalues() are gone, and methods like values() and items() return now iterators in Py 3. But at a quick glance I couldn't find any details whether an iterator will become invalid when changing the dict. |
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Ok no surprise that it works in Py 3. I assume the 2to3 translator is changing this line: for tset in self.__subjectIndex.itervalues():into: for tset in list(self.__subjectIndex.values()):which means the iterator / view is turned into a list before it is being iterated. Furthermore after some tests, and reading on python 3 views. The modification of a datastructure while iterating over it is undefined. Some of my tests where successful, some failed, and others returned really surprising results. In any way, I think we either have to copy the list of items to iterate (as the 2to3 translator does), or live with possible exceptions or even surprising results. |
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didn't break in py3 as 2to3 correctly handles the .values() by surrounding it with list() as gweis pointed out. |
mamash
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Feb 15, 2014
2013/12/31 RELEASE 4.1 ====================== This is a new minor version RDFLib, which includes a handful of new features: * A TriG parser was added (we already had a serializer) - it is up-to-date wrt. to the newest spec from: http://www.w3.org/TR/trig/ * The Turtle parser was made up to date wrt. to the latest Turtle spec. * Many more tests have been added - RDFLib now has over 2000 (passing!) tests. This is mainly thanks to the NT, Turtle, TriG, NQuads and SPARQL test-suites from W3C. This also included many fixes to the nt and nquad parsers. * ```ConjunctiveGraph``` and ```Dataset``` now support directly adding/removing quads with ```add/addN/remove``` methods. * ```rdfpipe``` command now supports datasets, and reading/writing context sensitive formats. * Optional graph-tracking was added to the Store interface, allowing empty graphs to be tracked for Datasets. The DataSet class also saw a general clean-up, see: RDFLib/rdflib#309 * After long deprecation, ```BackwardCompatibleGraph``` was removed. Minor enhancements/bugs fixed: ------------------------------ * Many code samples in the documentation were fixed thanks to @PuckCh * The new ```IOMemory``` store was optimised a bit * ```SPARQL(Update)Store``` has been made more generic. * MD5 sums were never reinitialized in ```rdflib.compare``` * Correct default value for empty prefix in N3 [#312]RDFLib/rdflib#312 * Fixed tests when running in a non UTF-8 locale [#344]RDFLib/rdflib#344 * Prefix in the original turtle have an impact on SPARQL query resolution [#313]RDFLib/rdflib#313 * Duplicate BNode IDs from N3 Parser [#305]RDFLib/rdflib#305 * Use QNames for TriG graph names [#330]RDFLib/rdflib#330 * \uXXXX escapes in Turtle/N3 were fixed [#335]RDFLib/rdflib#335 * A way to limit the number of triples retrieved from the ```SPARQLStore``` was added [#346]RDFLib/rdflib#346 * Dots in localnames in Turtle [#345]RDFLib/rdflib#345 [#336]RDFLib/rdflib#336 * ```BNode``` as Graph's public ID [#300]RDFLib/rdflib#300 * Introduced ordering of ```QuotedGraphs``` [#291]RDFLib/rdflib#291 2013/05/22 RELEASE 4.0.1 ======================== Following RDFLib tradition, some bugs snuck into the 4.0 release. This is a bug-fixing release: * the new URI validation caused lots of problems, but is nescessary to avoid ''RDF injection'' vulnerabilities. In the spirit of ''be liberal in what you accept, but conservative in what you produce", we moved validation to serialisation time. * the ```rdflib.tools``` package was missing from the ```setup.py``` script, and was therefore not included in the PYPI tarballs. * RDF parser choked on empty namespace URI [#288](RDFLib/rdflib#288) * Parsing from ```sys.stdin``` was broken [#285](RDFLib/rdflib#285) * The new IO store had problems with concurrent modifications if several graphs used the same store [#286](RDFLib/rdflib#286) * Moved HTML5Lib dependency to the recently released 1.0b1 which support python3 2013/05/16 RELEASE 4.0 ====================== This release includes several major changes: * The new SPARQL 1.1 engine (rdflib-sparql) has been included in the core distribution. SPARQL 1.1 queries and updates should work out of the box. * SPARQL paths are exposed as operators on ```URIRefs```, these can then be be used with graph.triples and friends: ```py # List names of friends of Bob: g.triples(( bob, FOAF.knows/FOAF.name , None )) # All super-classes: g.triples(( cls, RDFS.subClassOf * '+', None )) ``` * a new ```graph.update``` method will apply SPARQL update statements * Several RDF 1.1 features are available: * A new ```DataSet``` class * ```XMLLiteral``` and ```HTMLLiterals``` * ```BNode``` (de)skolemization is supported through ```BNode.skolemize```, ```URIRef.de_skolemize```, ```Graph.skolemize``` and ```Graph.de_skolemize``` * Handled of Literal equality was split into lexical comparison (for normal ```==``` operator) and value space (using new ```Node.eq``` methods). This introduces some slight backwards incomaptible changes, but was necessary, as the old version had inconsisten hash and equality methods that could lead the literals not working correctly in dicts/sets. The new way is more in line with how SPARQL 1.1 works. For the full details, see: https://github.com/RDFLib/rdflib/wiki/Literal-reworking * Iterating over ```QueryResults``` will generate ```ResultRow``` objects, these allow access to variable bindings as attributes or as a dict. I.e. ```py for row in graph.query('select ... ') : print row.age, row["name"] ``` * "Slicing" of Graphs and Resources as syntactic sugar: ([#271](RDFLib/rdflib#271)) ```py graph[bob : FOAF.knows/FOAF.name] -> generator over the names of Bobs friends ``` * The ```SPARQLStore``` and ```SPARQLUpdateStore``` are now included in the RDFLib core * The documentation has been given a major overhaul, and examples for most features have been added. Minor Changes: -------------- * String operations on URIRefs return new URIRefs: ([#258](RDFLib/rdflib#258)) ```py >>> URIRef('http://example.org/')+'test rdflib.term.URIRef('http://example.org/test') ``` * Parser/Serializer plugins are also found by mime-type, not just by plugin name: ([#277](RDFLib/rdflib#277)) * ```Namespace``` is no longer a subclass of ```URIRef``` * URIRefs and Literal language tags are validated on construction, avoiding some "RDF-injection" issues ([#266](RDFLib/rdflib#266)) * A new memory store needs much less memory when loading large graphs ([#268](RDFLib/rdflib#268)) * Turtle/N3 serializer now supports the base keyword correctly ([#248](RDFLib/rdflib#248)) * py2exe support was fixed ([#257](RDFLib/rdflib#257)) * Several bugs in the TriG serializer were fixed * Several bugs in the NQuads parser were fixed
This was referenced Jan 16, 2017
This was referenced Mar 16, 2017
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Hi,
When you try to iterate over a Graph and modify another Graph, and both Graphs are backed by the same IOMemory instance, then you might easily run into a problem where the index dictionaries that are used to iterrate, are being modified. (Resulting in a RuntimeError)
here is a little code snippet that demonstrates the issue.
This can be fixed by using .values() instead of .itervalues() in all graph iterating methods.
The question however is, what the desired behaviour would be. Current behaviour with the RuntimeError is IMO equally valid as the other where you would expect that this code should run cleanly. (I could see this causing some confusion with ConjunctiveGraph as well)
Any Suggestions?
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