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https://issues.apache.org/jira/browse/CASSANDRA-19814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17870702#comment-17870702
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Dmitry Konstantinov commented on CASSANDRA-19814:
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I am going to share a patch which makes UDT codec behaviour for 4.x driver
similar to 3.x version.
> UDT codec decode is too restrictive in decoding of unknown fields
> -----------------------------------------------------------------
>
> Key: CASSANDRA-19814
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19814
> Project: Cassandra
> Issue Type: Bug
> Components: Client/java-driver
> Reporter: Dmitry Konstantinov
> Assignee: Dmitry Konstantinov
> Priority: Normal
>
> The current UDT code logic in driver 4.x expects the number of UDT fields
> exactly equal to the number of fields in the schema version used to create
> the codec.
> As a result it makes applications less friendly to a live upgrade logic when
> we change DB schema and do a rolling restart of applications to switch from
> an old app version to a new one. In this scenario we can add a new field to
> UDT (backward compatible change) and a new application version can write this
> UDT with a new field filled but the old application version will fail to
> decode such UDT with the extra unknown field.
> Driver 3.x UDT codec has a different behaviour - the UDT codec logic reads
> known UDT fields received from network and ignores the unknown tail, which
> makes in tolerant to such schema changes:
> https://github.com/apache/cassandra-java-driver/blob/3.x/driver-core/src/main/java/com/datastax/driver/core/TypeCodec.java#L2202
> A code example to illustrate the issue:
> Schema
> {code:java}
> CREATE TYPE test_keyspace.basicInfoInner (
> weight text,
> height text
> );
> CREATE TYPE test_keyspace.basicInfo (
> birthday timestamp,
> nationality text,
> inner frozen<basicInfoInner>
> );
> CREATE TABLE test_keyspace.tableWithUdt
> (
> id varchar,
> value frozen<list<basicInfo>>,
> PRIMARY KEY (id)
> ); {code}
> Code:
> {code:java}
> CqlSession session = getSession();
> UdtCodec udtCodec = new UdtCodec(userDefinedType);
> TypeCodec<List<UdtValue>> listOfUdtCodec = TypeCodecs.listOf(udtCodec);
> {
> ResultSet resultSet = session.execute("select id, value from
> tableWithUdt");
> for (Row row : resultSet) {
> String id = row.getString(0);
> List<UdtValue> udtValueList = row.get(1, listOfUdtCodec);
> }
> }
> session.execute("ALTER TYPE basicInfo ADD details text");
> session.execute("INSERT INTO tableWithUdt (id, value) VALUES ('4', [\n" +
> " { birthday : '1993-06-18', " +
> " nationality : 'New Zealand', " +
> " inner: { weight : '70', height : '70' } " +
> " },\n" +
> " { birthday : '1993-06-19', " +
> " nationality : null, " +
> " inner: { weight : '70', height : null }, " +
> " details: 'added details'" + // <=== insert a value for the new
> added UDT field
> " }\n" +
> " ])");
> {
> ResultSet resultSet = session.execute("select id, value from
> tableWithUdt");
> for (Row row : resultSet) {
> String id = row.getString(0);
> // ==== UdtCodec throws IllegalArgumentException: Too many fields in
> encoded UDT value, expected 3 ====
> List<UdtValue> udtValueList = row.get(1, listOfUdtCodec);
> }
> }
> private static UserDefinedType getUserDefinedType(CqlSession session, String
> udtName) {
> return session.getMetadata()
> .getKeyspace(session.getKeyspace().orElseThrow(() -> new
> IllegalArgumentException("Udt name " + udtName + " can't be loaded due to
> null keyspace")))
> .orElseThrow(() -> new IllegalArgumentException("Metadata is not
> found"))
> .getUserDefinedType(udtName)
> .orElseThrow(() -> new IllegalArgumentException("Udt name " +
> udtName + " isn't found"));
> }
> {code}
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