JENA-1773: Remove any previous prefix setting.

jena-db/jena-dboe-storage/src/main/java/org/apache/jena/dboe/storage/prefixes/PrefixEntry.java

@@ -39,4 +39,9 @@ public String getPrefix() {
     public String getUri() {
         return uri;
     }
+
+    @Override
+    public String toString() {
+        return "PrefixEntry["+prefix+": <"+uri+">]";
+    }
 }

jena-db/jena-dboe-storage/src/main/java/org/apache/jena/dboe/storage/prefixes/PrefixLib.java

@@ -17,6 +17,8 @@
 
 package org.apache.jena.dboe.storage.prefixes;
 
+import java.util.Objects;
+
 import org.apache.jena.atlas.lib.Pair;
 import org.apache.jena.dboe.storage.StoragePrefixes;
 import org.apache.jena.graph.Node;
@@ -40,11 +42,23 @@ public static String canonicalPrefix(String prefix) {
 
     /** Canonical name for graphs */
     public static Node canonicalGraphName(Node graphName) {
+        if ( graphName == StoragePrefixes.nodeDefaultGraph) 
+            return graphName;
         if ( graphName == null || Quad.isDefaultGraph(graphName) )
             return StoragePrefixes.nodeDefaultGraph;
         return graphName;
     }
 
+    /**
+     * Is this the canonical, internal marker for the default graph for storage
+     * prefixes? ({@link StoragePrefixes#nodeDefaultGraph})
+     * 
+     * @param graphName
+     */
+    public static boolean isNodeDefaultGraph(Node graphName) {
+        return Objects.equals(StoragePrefixes.nodeDefaultGraph, graphName);
+    }
+
     /** abbreviate a uriStr, giving a string as a short form. If not possible return null.
      * This does not guarantee that the result is suitable for all RDF syntaxes.
      * Further checking for the rules of a particular syntax are necessary.

jena-db/jena-tdb2/src/main/java/org/apache/jena/tdb2/store/GraphViewSwitchable.java

@@ -136,7 +136,7 @@ class PrefixMapTDB2 extends PrefixMapBase {
         @Override
         protected StoragePrefixMap spm() {
             StoragePrefixes prefixes = getDSG().getPrefixes();
-            StoragePrefixMap view = Quad.isDefaultGraph(graphName)
+            StoragePrefixMap view = PrefixLib.isNodeDefaultGraph(graphName)
                 ? StoragePrefixesView.viewDefaultGraph(prefixes)
                 : StoragePrefixesView.viewGraph(prefixes, graphName);
             return view;

jena-db/jena-tdb2/src/main/java/org/apache/jena/tdb2/store/StoragePrefixesTDB.java

@@ -91,6 +91,8 @@ public void add_ext(Node graphNode, String prefix, String iriStr) {
         graphNode = PrefixLib.canonicalGraphName(graphNode);
         Node p = NodeFactory.createLiteral(prefix);
         Node u = NodeFactory.createURI(iriStr);
+        // Delete any existing old mapping of prefix.
+        remove_ext(graphNode, p, Node.ANY);
         prefixTable.addRow(graphNode,p,u);
     }
 
@@ -111,7 +113,7 @@ private void remove(Node g, Node p, Node u) {
     }
 
     /** Remove without checks - used by the bulkloader when it takes control of the transaction. */  
-    public void remove_ext(Node g, Node p, Node u) {
+    private void remove_ext(Node g, Node p, Node u) {
         // See add_ext
         g = PrefixLib.canonicalGraphName(g);
         Iterator<Tuple<Node>> iter = prefixTable.find(g, p, u);