The HBase translator translates INSERT as UPSERT, which is an "alias" for both INSERT and UPDATE statement. It means, if user issues same INSERT statement twice, no exception is thrown [1]. I expect that [2] could rewrite the data.

Additional note: I was not able to verify my assumption because of https://issues.jboss.org/browse/TEIID-3619

[1]
INSERT INTO smalla (intkey) VALUES (55) is translated as UPSERT INTO smalla (intkey) VALUES (55)
http://phoenix.apache.org/language/index.html#upsert_values

[2]
INSERT INTO smalla (intkey, name) VALUES (1, 'name1')
INSERT INTO smalla (intkey, name) VALUES (1, 'name2')