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# Source code for rdflib.plugins.sparql.update

    """

    Code for carrying out Update Operations

    """

    from rdflib import Graph, Variable

    from rdflib.plugins.sparql.sparql import QueryContext
    from rdflib.plugins.sparql.evalutils import _fillTemplate, _join
    from rdflib.plugins.sparql.evaluate import evalBGP, evalPart

    def _graphOrDefault(ctx, g):
        if g == 'DEFAULT':
            return ctx.graph
        else:
            return ctx.dataset.get_context(g)

    def _graphAll(ctx, g):
        """
        return a list of graphs
        """
        if g == 'DEFAULT':
            return [ctx.graph]
        elif g == 'NAMED':
            return [c for c in ctx.dataset.contexts()
                    if c.identifier != ctx.graph.identifier]
        elif g == 'ALL':
            return list(ctx.dataset.contexts())
        else:
            return [ctx.dataset.get_context(g)]

    def evalLoad(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#load
        """

        if u.graphiri:
            ctx.load(u.iri, default=False, publicID=u.graphiri)
        else:
            ctx.load(u.iri, default=True)

    def evalCreate(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#create
        """
        g = ctx.datset.get_context(u.graphiri)
        if len(g) > 0:
            raise Exception("Graph %s already exists." % g.identifier)
        raise Exception("Create not implemented!")

    def evalClear(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#clear
        """

        for g in _graphAll(ctx, u.graphiri):
            g.remove((None, None, None))

    def evalDrop(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#drop
        """
        if ctx.dataset.store.graph_aware:
            for g in _graphAll(ctx, u.graphiri):
                ctx.dataset.store.remove_graph(g)
        else:
            evalClear(ctx, u)

    def evalInsertData(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#insertData
        """
        # add triples
        g = ctx.graph
        g += u.triples

        # add quads
        # u.quads is a dict of graphURI=>[triples]
        for g in u.quads:
            cg = ctx.dataset.get_context(g)
            cg += u.quads[g]

    def evalDeleteData(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#deleteData
        """
        # remove triples
        g = ctx.graph
        g -= u.triples

        # remove quads
        # u.quads is a dict of graphURI=>[triples]
        for g in u.quads:
            cg = ctx.dataset.get_context(g)
            cg -= u.quads[g]

    def evalDeleteWhere(ctx, u):
        """
        http://www.w3.org/TR/sparql11-update/#deleteWhere
        """

        res = evalBGP(ctx, u.triples)
        for g in u.quads:
            cg = ctx.dataset.get_context(g)
            c = ctx.pushGraph(cg)
            res = _join(res, list(evalBGP(c, u.quads[g])))

        for c in res:
            g = ctx.graph
            g -= _fillTemplate(u.triples, c)

            for g in u.quads:
                cg = ctx.dataset.get_context(c.get(g))
                cg -= _fillTemplate(u.quads[g], c)

    def evalModify(ctx, u):

        originalctx = ctx

        # Using replaces the dataset for evaluating the where-clause
        if u.using:
            otherDefault = False
            for d in u.using:
                if d.default:

                    if not otherDefault:
                        # replace current default graph
                        dg = Graph()
                        ctx = ctx.pushGraph(dg)
                        otherDefault = True

                    ctx.load(d.default, default=True)

                elif d.named:
                    g = d.named
                    ctx.load(g, default=False)

        # "The WITH clause provides a convenience for when an operation
        # primarily refers to a single graph. If a graph name is specified
        # in a WITH clause, then - for the purposes of evaluating the
        # WHERE clause - this will define an RDF Dataset containing a
        # default graph with the specified name, but only in the absence
        # of USING or USING NAMED clauses. In the presence of one or more
        # graphs referred to in USING clauses and/or USING NAMED clauses,
        # the WITH clause will be ignored while evaluating the WHERE
        # clause."
        if not u.using and u.withClause:
            g = ctx.dataset.get_context(u.withClause)
            ctx = ctx.pushGraph(g)

        res = evalPart(ctx, u.where)

        if u.using:
            if otherDefault:
                ctx = originalctx  # restore original default graph
            if u.withClause:
                g = ctx.dataset.get_context(u.withClause)
                ctx = ctx.pushGraph(g)

        for c in res:
            dg = ctx.graph
            if u.delete:
                dg -= _fillTemplate(u.delete.triples, c)

                for g, q in u.delete.quads.iteritems():
                    cg = ctx.dataset.get_context(c.get(g))
                    cg -= _fillTemplate(q, c)

            if u.insert:
                dg += _fillTemplate(u.insert.triples, c)

                for g, q in u.insert.quads.iteritems():
                    cg = ctx.dataset.get_context(c.get(g))
                    cg += _fillTemplate(q, c)

    def evalAdd(ctx, u):
        """

        add all triples from src to dst

        http://www.w3.org/TR/sparql11-update/#add
        """
        src, dst = u.graph

        srcg = _graphOrDefault(ctx, src)
        dstg = _graphOrDefault(ctx, dst)

        if srcg.identifier == dstg.identifier:
            return

        dstg += srcg

    def evalMove(ctx, u):
        """

        remove all triples from dst
        add all triples from src to dst
        remove all triples from src

        http://www.w3.org/TR/sparql11-update/#move
        """

        src, dst = u.graph

        srcg = _graphOrDefault(ctx, src)
        dstg = _graphOrDefault(ctx, dst)

        if srcg.identifier == dstg.identifier:
            return

        dstg.remove((None, None, None))

        dstg += srcg

        if ctx.dataset.store.graph_aware:
            ctx.dataset.store.remove_graph(srcg)
        else:
            srcg.remove((None, None, None))

    def evalCopy(ctx, u):
        """

        remove all triples from dst
        add all triples from src to dst

        http://www.w3.org/TR/sparql11-update/#copy
        """

        src, dst = u.graph

        srcg = _graphOrDefault(ctx, src)
        dstg = _graphOrDefault(ctx, dst)

        if srcg.identifier == dstg.identifier:
            return

        dstg.remove((None, None, None))

        dstg += srcg

    def evalUpdate(graph, update, initBindings=None):
        """

        http://www.w3.org/TR/sparql11-update/#updateLanguage

        'A request is a sequence of operations [...] Implementations MUST
        ensure that operations of a single request are executed in a
        fashion that guarantees the same effects as executing them in
        lexical order.

        Operations all result either in success or failure.

        If multiple operations are present in a single request, then a
        result of failure from any operation MUST abort the sequence of
        operations, causing the subsequent operations to be ignored.'

        This will return None on success and raise Exceptions on error

        """

        for u in update:

            ctx = QueryContext(graph)
            ctx.prologue = u.prologue

            if initBindings:
                for k, v in initBindings.iteritems():
                    if not isinstance(k, Variable):
                        k = Variable(k)
                    ctx[k] = v
                # ctx.push()  # nescessary?

            try:
                if u.name == 'Load':
                    evalLoad(ctx, u)
                elif u.name == 'Clear':
                    evalClear(ctx, u)
                elif u.name == 'Drop':
                    evalDrop(ctx, u)
                elif u.name == 'Create':
                    evalCreate(ctx, u)
                elif u.name == 'Add':
                    evalAdd(ctx, u)
                elif u.name == 'Move':
                    evalMove(ctx, u)
                elif u.name == 'Copy':
                    evalCopy(ctx, u)
                elif u.name == 'InsertData':
                    evalInsertData(ctx, u)
                elif u.name == 'DeleteData':
                    evalDeleteData(ctx, u)
                elif u.name == 'DeleteWhere':
                    evalDeleteWhere(ctx, u)
                elif u.name == 'Modify':
                    evalModify(ctx, u)
                else:
                    raise Exception('Unknown update operation: %s' % (u,))
            except:
                if not u.silent:
                    raise

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