Skip to content

Commit

Permalink
Add support for query pass-through function in ClickHouse
Browse files Browse the repository at this point in the history
  • Loading branch information
ebyhr committed Jun 30, 2024
1 parent ed6a609 commit 35cb1a2
Show file tree
Hide file tree
Showing 3 changed files with 40 additions and 1 deletion.
36 changes: 36 additions & 0 deletions docs/src/main/sphinx/connector/clickhouse.md
Original file line number Diff line number Diff line change
Expand Up @@ -332,6 +332,42 @@ statements, the connector supports the following features:
```{include} alter-schema-limitation.fragment
```

## Table functions

The connector provides specific {doc}`table functions </functions/table>` to
access ClickHouse.

(clickhouse-query-function)=
### `query(varchar) -> table`

The `query` function allows you to query the underlying database directly. It
requires syntax native to ClickHouse, because the full query is pushed down and
processed in ClickHouse. This can be useful for accessing native features which
are not available in Trino or for improving query performance in situations
where running a query natively may be faster.

```{include} query-passthrough-warning.fragment
```

As a simple example, query the `example` catalog and select an entire table:

```
SELECT
*
FROM
TABLE(
example.system.query(
query => 'SELECT
*
FROM
tpch.nation'
)
);
```

```{include} query-table-function-ordering.fragment
```

## Performance

The connector includes a number of performance improvements, detailed in the
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -29,10 +29,13 @@
import io.trino.plugin.jdbc.JdbcClient;
import io.trino.plugin.jdbc.JdbcMetadataConfig;
import io.trino.plugin.jdbc.credential.CredentialProvider;
import io.trino.plugin.jdbc.ptf.Query;
import io.trino.spi.function.table.ConnectorTableFunction;

import java.util.Properties;

import static com.clickhouse.client.config.ClickHouseClientOption.USE_BINARY_STRING;
import static com.google.inject.multibindings.Multibinder.newSetBinder;
import static io.airlift.configuration.ConfigBinder.configBinder;
import static io.trino.plugin.clickhouse.ClickHouseClient.DEFAULT_DOMAIN_COMPACTION_THRESHOLD;
import static io.trino.plugin.jdbc.JdbcModule.bindSessionPropertiesProvider;
Expand All @@ -50,6 +53,7 @@ public void configure(Binder binder)
bindTablePropertiesProvider(binder, ClickHouseTableProperties.class);
configBinder(binder).bindConfigDefaults(JdbcMetadataConfig.class, config -> config.setDomainCompactionThreshold(DEFAULT_DOMAIN_COMPACTION_THRESHOLD));
binder.install(new DecimalModule());
newSetBinder(binder, ConnectorTableFunction.class).addBinding().toProvider(Query.class).in(Scopes.SINGLETON);
}

@Provides
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,6 @@ protected boolean hasBehavior(TestingConnectorBehavior connectorBehavior)
SUPPORTS_ARRAY,
SUPPORTS_DELETE,
SUPPORTS_DROP_NOT_NULL_CONSTRAINT,
SUPPORTS_NATIVE_QUERY,
SUPPORTS_NEGATIVE_DATE,
SUPPORTS_PREDICATE_PUSHDOWN_WITH_VARCHAR_INEQUALITY,
SUPPORTS_ROW_TYPE,
Expand Down

0 comments on commit 35cb1a2

Please sign in to comment.