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https://issues.apache.org/jira/browse/CASSANDRA-14638?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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C. Scott Andreas reassigned CASSANDRA-14638:
--------------------------------------------
Assignee: C. Scott Andreas
> Column result order can change in 'SELECT *' results when upgrading from 2.1
> to 3.0 causing response corruption for queries using prepared statements when
> static columns are used
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-14638
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14638
> Project: Cassandra
> Issue Type: Bug
> Environment: Single C* node ccm cluster upgraded from C* 2.1.20 to
> 3.0.17
> Reporter: Andy Tolbert
> Assignee: C. Scott Andreas
> Priority: Major
>
> When performing an upgrade from C* 2.1.20 to 3.0.17 I observed that the order
> of columns returned from a 'SELECT *' query changes, particularly when static
> columns are involved.
> This may not seem like that much of a problem, however if using Prepared
> Statements, any clients that remain connected during the upgrade may
> encounter issues consuming results from these queries, as data is reordered
> and the client not aware of it. The result definition is sent in the
> original prepared statement response, so if order changes the client has no
> way of knowing (until C* 4.0 via CASSANDRA-10786) without re-preparing, which
> is non-trivial as most client drivers cache prepared statements.
> This could lead to reading the wrong values for columns, which could result
> in some kind of deserialization exception or if the data types of the
> switched columns are compatible, the wrong values. This happens even if the
> client attempts to retrieve a column value by name (i.e. row.getInt("colx")).
> Unfortunately I don't think there is an easy fix for this. If the order was
> changed back to the previous format, you risk issues for users upgrading from
> older 3.0 version. I think it would be nice to add a note in the NEWS file
> in the 3.0 upgrade section that describes this issue, and how to work around
> it (specify all column names of interest explicitly in query).
> Example schema and code to reproduce:
>
> {noformat}
> create keyspace ks with replication = {'class': 'SimpleStrategy',
> 'replication_factor': 1};
> create table ks.tbl (p0 text,
> p1 text,
> m map<text, text> static,
> t text,
> u text static,
> primary key (p0, p1)
> );
> insert into ks.tbl (p0, p1, m, t, u) values ('p0', 'p1', { 'm0' : 'm1' },
> 't', 'u');{noformat}
>
> When querying with 2.1 you'll observe the following order via cqlsh:
> {noformat}
> p0 | p1 | m | u | t
> ----+----+--------------+---+---
> p0 | p1 | {'m0': 'm1'} | u | t{noformat}
>
> With 3.0, observe that u and m are transposed:
>
> {noformat}
> p0 | p1 | u | m | t
> ----+----+---+--------------+---
> p0 | p1 | u | {'m0': 'm1'} | t{noformat}
>
>
> {code:java}
> import com.datastax.driver.core.BoundStatement;
> import com.datastax.driver.core.Cluster;
> import com.datastax.driver.core.ColumnDefinitions;
> import com.datastax.driver.core.PreparedStatement;
> import com.datastax.driver.core.ResultSet;
> import com.datastax.driver.core.Row;
> import com.datastax.driver.core.Session;
> import com.google.common.util.concurrent.Uninterruptibles;
> import java.util.concurrent.TimeUnit;
> public class LiveUpgradeTest {
> public static void main(String args[]) {
> Cluster cluster = Cluster.builder().addContactPoints("127.0.0.1").build();
> try {
> Session session = cluster.connect();
> PreparedStatement p = session.prepare("SELECT * from ks.tbl");
> BoundStatement bs = p.bind();
> // continually query every 30 seconds
> while (true) {
> try {
> ResultSet r = session.execute(bs);
> Row row = r.one();
> int i = 0;
> // iterate over the result metadata in order printing the
> // index, name, type, and length of the first row of data.
> for (ColumnDefinitions.Definition d : r.getColumnDefinitions()) {
> System.out.println(
> i++
> + ": "
> + d.getName()
> + " -> "
> + d.getType()
> + " -> val = "
> + row.getBytesUnsafe(d.getName()).array().length);
> }
> } catch (Throwable t) {
> t.printStackTrace();
> } finally {
> Uninterruptibles.sleepUninterruptibly(30, TimeUnit.SECONDS);
> }
> }
> } finally {
> cluster.close();
> }
> }
> }
> {code}
> To reproduce, set up a cluster, the schema, and run this script. Then
> upgrade the cluster to 3.0.17 (with ccm, ccm stop; ccm node1 setdir -v
> 3.0.17; ccm start works) and observe after the client is able to reconnect
> that the results are in a different order. i.e.:
>
> With 2.x:
>
> {noformat}
> 0: p0 -> varchar -> val = 2
> 1: p1 -> varchar -> val = 2
> 2: m -> map<varchar, varchar> -> val = 16
> 3: u -> varchar -> val = 1
> 4: t -> varchar -> val = 1{noformat}
>
> With 3.x:
>
> {noformat}
> 0: p0 -> varchar -> val = 2
> 1: p1 -> varchar -> val = 2
> 2: m -> map<varchar, varchar> -> val = 1
> 3: u -> varchar -> val = 16 (<-- the data for 'm' is now at index 3)
> 4: t -> varchar -> val = 1{noformat}
>
>
>
>
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