lewismc commented on a change in pull request #156: GORA 411 - Add exists(key)
to DataStore interface
URL: https://github.com/apache/gora/pull/156#discussion_r270284347
##########
File path:
gora-cassandra/src/main/java/org/apache/gora/cassandra/serializers/CassandraQueryFactory.java
##########
@@ -313,6 +313,24 @@ static String
getSelectObjectWithFieldsQuery(CassandraMapping mapping, String[]
String[] columnNames = getColumnNames(mapping, keyFields);
return processKeys(columnNames, select);
}
+
+ /**
+ * This method returns CQL Select query to check if a key exists.
+ * This method is used for Avro Serialization
+ * refer:
http://docs.datastax.com/en/cql/3.3/cql/cql_reference/cqlSelect.html
+ *
+ * @param mapping Cassandra Mapping {@link CassandraMapping}
+ * @param keyFields key fields
+ * @return CQL Query
+ */
+ static String getCheckExistsQuery(CassandraMapping mapping, List<String>
keyFields) {
+ Select select =
QueryBuilder.select().countAll().from(mapping.getKeySpace().getName(),
mapping.getCoreName());
+ if (Boolean.parseBoolean(mapping.getProperty("allowFiltering"))) {
Review comment:
We need some example showing this or maybe for documentation somewhere to
reflect this otherwise no-one is going to know it exists.
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