Finding Subnodes on All Levels
The next example will search a slightly more complex set of subnodes. We’ll add new child node "dogs" to ^myNames and use it as the target node for this example:
^myNames (valueless root node)
^myNames("dogs") (valueless level 1 node)
^myNames("dogs","Balto") = 6
^myNames("dogs","Hachiko") = 8
^myNames("dogs","Lassie") (valueless level 2 node)
^myNames("dogs","Lassie","Timmy") = 10 (level 3 node)
^myNames("dogs","Whitefang") = 7
^myNames("people") (valueless level 1 node)
[five child nodes] (as listed in previous example)
Target node ^myNames("dogs") has five subnodes, but only four of them are child nodes. In addition to the four level 2 subnodes, there is also a level 3 subnode, ^myNames("dogs","Lassie","Timmy"). The search will not find "Timmy" because this subnode is the child of "Lassie" (not "dogs"), and therefore is not a sibling of the others.
Note:
Subscript Lists and Node Levels
The term node level refers to the number of subscripts in the subscript list. For example, ^myGlobal("a","b","c") is a “level 3 node,” which is just another way of saying “a node with three subscripts.”
Although node ^myNames("dogs","Lassie") has a child node, it does not have a value. A call to getValue() will return null in this case. The following example searches for children of ^myNames("dogs") in reverse collation order:
Get nodes in reverse order from last node under ^myNames("dogs")
// Read child nodes in descending order while iter.next() is true
System.out.print("Descend from last node:");
try {
IRISIterator iter = irisjv.getIRISIterator("myNames","dogs");
while (iter.hasPrevious()) {
iter.previous();
System.out.print(" \"" + iter.getSubscriptValue() + "\"");
if (iter.getValue()!=null) System.out.print("=" + iter.getValue());
};
} catch (Exception e) {
System.out.println( e.getMessage());
}
This code prints the following line:
Descend from last node: "Whitefang"=7 "Lassie" "Hachiko"=8 "Balto"=6
In the previous example, the search misses several of the nodes in global array ^myNames because the scope of the search is restricted in various ways:
-
Node ^myNames("dogs","Lassie","Timmy") is not found because it is not a level 2 subnode of ^myNames("dogs").
-
Level 2 nodes under ^myNames("people") are not found because they are not siblings of the level 2 nodes under ^myNames("dogs").
The problem in both cases is that previous() and next() only find nodes that are under the same parent and on the same level as the starting address. You must specify a different starting address for each group of sibling nodes.
In most cases, you will probably be processing a known structure, and will traverse the various levels with simple nested calls. In the less common case where a structure has an arbitrary number of levels, the following jdbc.IRIS method can be used to determine if a given node has subnodes:
If isDefined() returns 10 or 11, subnodes exist and can be processed by creating an iterator as described in the previous examples. A recursive algorithm could use this test to process any number of levels.
