Vertica connector#
The Vertica connector allows querying a Vertica database as an external data source.
Requirements#
To connect to Vertica, you need:
Vertica 9.1.x or higher.
Network access from the coordinator and workers to the Vertica server. Port 5433 is the default port.
Configuration#
Create a catalog properties file in etc/catalog
named example.properties
to
access the configured Vertica database in the example
catalog. Replace example
with your database name or some other descriptive name of the catalog. Configure
the usage of the connector by specifying the name vertica
and replace the
connection properties as appropriate for your setup.
connector.name=vertica
connection-url=jdbc:vertica://example.net:5433/test_db
connection-user=root
connection-password=secret
The connection-user
and connection-password
are typically required and
determine the user credentials for the connection, often a service user. You can
use secrets to avoid actual values in the catalog
properties files.
General configuration properties#
The following table describes general catalog configuration properties for the connector:
Property name |
Description |
---|---|
|
Support case insensitive schema and table names. Defaults to |
|
Duration for which case insensitive schema and table
names are cached. Defaults to |
|
Path to a name mapping configuration file in JSON format that allows
Trino to disambiguate between schemas and tables with similar names in
different cases. Defaults to |
|
Frequency with which Trino checks the name matching configuration file
for changes. The duration value defaults to |
|
Duration for which metadata, including table and
column statistics, is cached. Defaults to |
|
Cache the fact that metadata, including table and column statistics, is
not available. Defaults to |
|
Duration for which schema metadata is cached.
Defaults to the value of |
|
Duration for which table metadata is cached.
Defaults to the value of |
|
Duration for which tables statistics are cached.
Defaults to the value of |
|
Maximum number of objects stored in the metadata cache. Defaults to |
|
Maximum number of statements in a batched execution. Do not change
this setting from the default. Non-default values may negatively
impact performance. Defaults to |
|
Push down dynamic filters into JDBC queries. Defaults to |
|
Maximum duration for which Trino waits for dynamic
filters to be collected from the build side of joins before starting a
JDBC query. Using a large timeout can potentially result in more detailed
dynamic filters. However, it can also increase latency for some queries.
Defaults to |
Appending query metadata#
The optional parameter query.comment-format
allows you to configure a SQL
comment that is sent to the datasource with each query. The format of this
comment can contain any characters and the following metadata:
$QUERY_ID
: The identifier of the query.$USER
: The name of the user who submits the query to Trino.$SOURCE
: The identifier of the client tool used to submit the query, for exampletrino-cli
.$TRACE_TOKEN
: The trace token configured with the client tool.
The comment can provide more context about the query. This additional
information is available in the logs of the datasource. To include environment
variables from the Trino cluster with the comment , use the
${ENV:VARIABLE-NAME}
syntax.
The following example sets a simple comment that identifies each query sent by Trino:
query.comment-format=Query sent by Trino.
With this configuration, a query such as SELECT * FROM example_table;
is
sent to the datasource with the comment appended:
SELECT * FROM example_table; /*Query sent by Trino.*/
The following example improves on the preceding example by using metadata:
query.comment-format=Query $QUERY_ID sent by user $USER from Trino.
If Jane
sent the query with the query identifier
20230622_180528_00000_bkizg
, the following comment string is sent to the
datasource:
SELECT * FROM example_table; /*Query 20230622_180528_00000_bkizg sent by user Jane from Trino.*/
Note
Certain JDBC driver settings and logging configurations might cause the comment to be removed.
Domain compaction threshold#
Pushing down a large list of predicates to the data source can compromise
performance. Trino compacts large predicates into a simpler range predicate
by default to ensure a balance between performance and predicate pushdown.
If necessary, the threshold for this compaction can be increased to improve
performance when the data source is capable of taking advantage of large
predicates. Increasing this threshold may improve pushdown of large
dynamic filters.
The domain-compaction-threshold
catalog configuration property or the
domain_compaction_threshold
catalog session property can be used to adjust the default value of
256
for this threshold.
Case insensitive matching#
When case-insensitive-name-matching
is set to true
, Trino
is able to query non-lowercase schemas and tables by maintaining a mapping of
the lowercase name to the actual name in the remote system. However, if two
schemas and/or tables have names that differ only in case (such as “customers”
and “Customers”) then Trino fails to query them due to ambiguity.
In these cases, use the case-insensitive-name-matching.config-file
catalog
configuration property to specify a configuration file that maps these remote
schemas/tables to their respective Trino schemas/tables:
{
"schemas": [
{
"remoteSchema": "CaseSensitiveName",
"mapping": "case_insensitive_1"
},
{
"remoteSchema": "cASEsENSITIVEnAME",
"mapping": "case_insensitive_2"
}],
"tables": [
{
"remoteSchema": "CaseSensitiveName",
"remoteTable": "tablex",
"mapping": "table_1"
},
{
"remoteSchema": "CaseSensitiveName",
"remoteTable": "TABLEX",
"mapping": "table_2"
}]
}
Queries against one of the tables or schemes defined in the mapping
attributes are run against the corresponding remote entity. For example, a query
against tables in the case_insensitive_1
schema is forwarded to the
CaseSensitiveName schema and a query against case_insensitive_2
is forwarded
to the cASEsENSITIVEnAME
schema.
At the table mapping level, a query on case_insensitive_1.table_1
as
configured above is forwarded to CaseSensitiveName.tablex
, and a query on
case_insensitive_1.table_2
is forwarded to CaseSensitiveName.TABLEX
.
By default, when a change is made to the mapping configuration file, Trino must
be restarted to load the changes. Optionally, you can set the
case-insensitive-name-mapping.refresh-period
to have Trino refresh the
properties without requiring a restart:
case-insensitive-name-mapping.refresh-period=30s
Type mapping#
Because Trino and Vertica each support types that the other does not, this connector modifies some types when reading or writing data. Data types may not map the same way in both directions between Trino and the data source. Refer to the following sections for type mapping in each direction.
Vertica to Trino type mapping#
The connector maps Vertica types to the corresponding Trino types according to the following table:
Vertica type |
Trino type |
Notes |
---|---|---|
|
|
|
|
|
Vertica treats TINYINT, SMALLINT, INTEGER, and BIGINT as synonyms for the same 64-bit BIGINT data type |
|
|
Vertica treats FLOAT and REAL as the same 64-bit IEEE FLOAT |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
No other types are supported.
Unsupported Vertica types can be converted to VARCHAR
with the
vertica.unsupported_type_handling
session property. The default value for
this property is IGNORE
.
SET SESSION vertica.unsupported_type_handling='CONVERT_TO_VARCHAR';
Trino to Vertica type mapping#
The connector maps Trino types to the corresponding Vertica types according to the following table:
Trino type |
Vertica type |
---|---|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
No other types are supported.
Type mapping configuration properties#
The following properties can be used to configure how data types from the connected data source are mapped to Trino data types and how the metadata is cached in Trino.
Property name |
Description |
Default value |
---|---|---|
|
Configure how unsupported column data types are handled:
The respective catalog session property is |
|
|
Allow forced mapping of comma separated lists of data types to convert to
unbounded |
SQL support#
The connector provides read and write access to data and metadata in Vertica. In addition to the globally available and read operation statements, the connector supports the following features:
ALTER TABLE excluding
DROP COLUMN
ALTER TABLE RENAME TO#
The connector does not support renaming tables across multiple schemas. For example, the following statement is supported:
ALTER TABLE example.schema_one.table_one RENAME TO example.schema_one.table_two
The following statement attempts to rename a table across schemas, and therefore is not supported:
ALTER TABLE example.schema_one.table_one RENAME TO example.schema_two.table_two
Table functions#
The connector provides specific table functions to access Vertica.
query(VARCHAR) -> table
#
The query
function allows you to query the underlying database directly. It
requires syntax native to the data source, because the full query is pushed down
and processed in the data source. This can be useful for accessing native
features or for improving query performance in situations where running a query
natively may be faster.
The query
table function is available in the system
schema of any
catalog that uses the Vertica connector, such as example
. The
following example passes myQuery
to the data source. myQuery
has to be a
valid query for the data source, and is required to return a table as a result:
SELECT
*
FROM
TABLE(
example.system.query(
query => 'myQuery'
)
);
Note
The query engine does not preserve the order of the results of this
function. If the passed query contains an ORDER BY
clause, the
function result may not be ordered as expected.
Performance#
The connector includes a number of performance features, detailed in the following sections.
Pushdown#
The connector supports pushdown for a number of operations:
Join pushdown#
The join-pushdown.enabled
catalog configuration property or
join_pushdown_enabled
catalog session property control whether the connector pushes
down join operations. The property defaults to false
, and enabling join
pushdowns may negatively impact performance for some queries.
Table statistics#
The cost-based optimizer can use table statistics from the Vertica database to improve query performance.
Support for table statistics is disabled by default. You can enable it with the
catalog property statistics.enabled
set to true
. In addition, the
connection-user
configured in the catalog must have superuser permissions in
Vertica to gather and populate statistics.
You can view statistics using SHOW STATS.