Apache Ignite Continuous Queries : How to get the field names and field values in the listener updates when there are dynamic fields? - sql

Question

I am working on a POC on whether or not we should go ahead with Apache Ignite both for commerical and enterprise use. There is a use case though that we are trying to find an answer for.
Preconditions
Dynamically creation of tables i.e. there may be new fields that come to be put into the cache. Meaning there is no precompiled POJO(Model) defining the attributes of the table/cache.
Use case
I would like to write a SELECT continuous query where it gives me the results that are modified. So I wrote that query but the problem is that when the listener gets a notification, I am not able to find all the field names that are modified from any method call. I would like to be able to get all the field names and field values in some sort of Map, which I can use and then submit to other systems.

Answer 1

You could track all modified field values using binary object and continuous query:
IgniteCache<Integer, BinaryObject> cache = ignite.cache("person").withKeepBinary();
ContinuousQuery<Integer, BinaryObject> query = new ContinuousQuery<>();
query.setLocalListener(events -> {
for (CacheEntryEvent<? extends Integer, ? extends BinaryObject> event : events) {
BinaryType type = ignite.binary().type("Person");
if (event.getOldValue() != null && event.getValue() != null) {
HashMap<String,Object> oldProps = new HashMap<>();
HashMap<String,Object> newProps = new HashMap<>();
for (String field : type.fieldNames()) {
oldProps.put(field,event.getOldValue().field(field));
newProps.put(field,event.getValue().field(field));
}
com.google.common.collect.MapDifference<Object, Object> diff = com.google.common.collect.Maps.difference(oldProps, newProps);
System.out.println(diff.entriesDiffering());
}
}
});
cache.query(query);
cache.put(1, ignite.binary().builder("Person").setField("name","Alice").build());
cache.put(1, ignite.binary().builder("Person").setField("name","Bob").build());