[ https://issues.apache.org/jira/browse/CASSANDRA-14638?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Aleksey Yeschenko updated CASSANDRA-14638: ------------------------------------------ Fix Version/s: 3.11.x 3.0.x > 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: Aleksey Yeschenko > Priority: Major > Fix For: 3.0.x, 3.11.x > > > 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} > > > > -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org