Upgrading Impala

Upgrading Impala involves building or acquiring new Impala-related binaries, and then restarting Impala services.

Upgrading Impala

Shut down all Impala-related daemons on all relevant hosts in the cluster:
1. Stop impalad on each Impala node in your cluster:
```
$ sudo service impala-server stop
```
2. Stop any instances of the state store in your cluster:
```
$ sudo service impala-state-store stop
```
3. Stop any instances of the catalog service in your cluster:
```
$ sudo service impala-catalog stop
```
Follow the build procedure in the README.md file to produce new Impala binaries.
Replace the binaries for all Impala-related daemons on all relevant hosts in the cluster.
Check if there are new recommended or required configuration settings to put into place in the configuration files, typically under /etc/impala/conf. See Post-Installation Configuration for Impala for settings related to performance and scalability.
Restart all Impala-related daemons on all relevant hosts in the cluster:
1. Restart the Impala state store service on the desired nodes in your cluster. Expect to see a process named statestored if the service started successfully.
```
$ sudo service impala-state-store start
$ ps ax | grep [s]tatestored
 6819 ?        Sl     0:07 /usr/lib/impala/sbin/statestored -log_dir=/var/log/impala -state_store_port=24000
```
  Restart the state store service before the Impala server service to avoid "Not connected" errors when you run impala-shell.
2. Restart the Impala catalog service on whichever host it runs on in your cluster. Expect to see a process named catalogd if the service started successfully.
```
$ sudo service impala-catalog restart
$ ps ax | grep [c]atalogd
 6068 ?        Sl     4:06 /usr/lib/impala/sbin/catalogd
```
3. Restart the Impala daemon service on each node in your cluster. Expect to see a process named impalad if the service started successfully.
```
$ sudo service impala-server start
$ ps ax | grep [i]mpalad
 7936 ?        Sl     0:12 /usr/lib/impala/sbin/impalad -log_dir=/var/log/impala -state_store_port=24000
 -state_store_host=127.0.0.1 -be_port=22000
```

Note:

If the services did not start successfully (even though the sudo service command might display [OK]), check for errors in the Impala log file, typically in /var/log/impala.

Impala Upgrade Considerations

List of Reserved Words Updated in Impala 3.0

The list of reserved words in Impala was updated in Impala 3.0. If you need to use a reserved word as an identifier, e.g. a table name, enclose the word in back-ticks.

If you need to use the reserved words from previous versions of Impala, set the impalad and catalogd startup flag. Note that this startup option will be deprecated in a future release.

--reserved_words_version=2.11.0

Decimal V2 Used by Default in Impala 3.0

In Impala, two different implementations of DECIMAL types are supported. Starting in Impala 3.0, DECIMAL V2 is used by default. See DECIMAL Type for detail information.

If you need to continue using the first version of the DECIMAL type for the backward compatibility of your queries, set the DECIMAL_V2 query option to FALSE:

SET DECIMAL_V2=FALSE;

Behavior of Column Aliases Changed in Impala 3.0

To conform to the SQL standard, Impala no longer performs alias substitution in the subexpressions of GROUP BY, HAVING, and ORDER BY. See Overview of Impala Aliases for examples of supported and unsupported aliases syntax.

Default PARQUET_ARRAY_RESOLUTION Changed in Impala 3.0

The default value for the PARQUET_ARRAY_RESOLUTION was changed to THREE_LEVEL in Impala 3.0, to match the Parquet standard 3-level encoding.

See PARQUET_ARRAY_RESOLUTION Query Option (Impala 2.9 or higher only) for the information about the query option.

Enable Clustering Hint for Inserts

In Impala 3.0, the clustered hint is enabled by default. The hint adds a local sort by the partitioning columns to a query plan.

The clustered hint is only effective for HDFS and Kudu tables.

As in previous versions, the noclustered hint prevents clustering. If a table has ordering columns defined, the noclustered hint is ignored with a warning.

Deprecated Query Options Removed in Impala 3.0

The following query options have been deprecated for several releases and removed:

DEFAULT_ORDER_BY_LIMIT
ABORT_ON_DEFAULT_LIMIT_EXCEEDED
V_CPU_CORES
RESERVATION_REQUEST_TIMEOUT
RM_INITIAL_MEM
SCAN_NODE_CODEGEN_THRESHOLD
MAX_IO_BUFFERS
RM_INITIAL_MEM
DISABLE_CACHED_READS

Fine-grained Privileges Added in Impala 3.0

Starting in Impala 3.0, finer grained privileges are enforced, such as the REFRESH, CREATE, DROP, and ALTER privileges. In particular, running REFRESH or INVALIDATE METADATA now requires the new REFRESH privilege. Users who did not previously have the ALL privilege will no longer be able to run REFRESH or INVALIDATE METADATA after an upgrade. Those users need to have the REFRESH or ALL privilege granted to run REFRESH or INVALIDATE METADATA.

See GRANT Statement (Impala 2.0 or higher only) for the new privileges, the scope, and other information about the new privileges.

refresh_after_connect Impala Shell Option Removed in Impala 3.0

The deprecated refresh_after_connect option was removed from Impala Shell in Impala 3.0

Default Setting Changes

Release Changed	Setting	Default Value
Impala 2.12	`compact_catalog_topic` `impalad` flag	`true`
Impala 2.12	`max_cached_file_handles` `impalad` flag	`20000`
Impala 3.0	`PARQUET_ARRAY_RESOLUTION` query option	`THREE_LEVEL`