Phoenix коннектор#

Примечание

Ниже приведена оригинальная документация Trino. Скоро мы ее переведем на русский язык и дополним полезными примерами.

The Phoenix connector allows querying data stored in Apache HBase using Apache Phoenix.

Requirements#

To query HBase data through Phoenix, you need:

Network access from the Trino coordinator and workers to the ZooKeeper servers. The default port is 2181.
A compatible version of Phoenix: all 5.x versions starting from 5.1.0 are supported.

Конфигурация#

To configure the Phoenix connector, create a catalog properties file etc/catalog/phoenix.properties with the following contents, replacing host1,host2,host3 with a comma-separated list of the ZooKeeper nodes used for discovery of the HBase cluster:

connector.name=phoenix5
phoenix.connection-url=jdbc:phoenix:host1,host2,host3:2181:/hbase
phoenix.config.resources=/path/to/hbase-site.xml

The optional paths to Hadoop resource files, such as hbase-site.xml are used to load custom Phoenix client connection properties.

The following Phoenix-specific configuration properties are available:

Property name	Required	Description
`phoenix.connection-url`	Yes	`jdbc:phoenix[:zk_quorum][:zk_port][:zk_hbase_path]`. The `zk_quorum` is a comma separated list of ZooKeeper servers. The `zk_port` is the ZooKeeper port. The `zk_hbase_path` is the HBase root znode path, that is configurable using `hbase-site.xml`. By default the location is `/hbase`
`phoenix.config.resources`	No	Comma-separated list of configuration files (e.g. `hbase-site.xml`) to use for connection properties. These files must exist on the machines running Trino.
`phoenix.max-scans-per-split`	No	Maximum number of HBase scans that will be performed in a single split. Default is 20. Lower values will lead to more splits in Trino. Can also be set via session propery `max_scans_per_split`. For details see: https://phoenix.apache.org/update_statistics.html. (This setting has no effect when guideposts are disabled in Phoenix.)

General configuration properties#

The following table describes general catalog configuration properties for the connector:

Property name	Description	Default value
`case-insensitive-name-matching`	Support case insensitive schema and table names.	`false`
`case-insensitive-name-matching.cache-ttl`		`1m`
`case-insensitive-name-matching.config-file`	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.	`null`
`case-insensitive-name-matching.config-file.refresh-period`	Frequency with which Trino checks the name matching configuration file for changes.	`0` (refresh disabled)
`metadata.cache-ttl`	Duration for which metadata, including table and column statistics, is cached.	`0` (caching disabled)
`metadata.cache-missing`	Cache the fact that metadata, including table and column statistics, is not available	`false`
`metadata.cache-maximum-size`	Maximum number of objects stored in the metadata cache	`10000`
`write.batch-size`	Maximum number of statements in a batched execution. Do not change this setting from the default. Non-default values may negatively impact performance.	`1000`
`dynamic-filtering.enabled`	Push down dynamic filters into JDBC queries	`true`
`dynamic-filtering.wait-timeout`	Maximum duration for which Trino will wait 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.	`20s`

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 5000 for this threshold.

Procedures#

system.flush_metadata_cache()

Flush JDBC metadata caches. For example, the following system call flushes the metadata caches for all schemas in the example catalog
```
USE example.myschema;
CALL system.flush_metadata_cache();
```

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

Non-transactional INSERT#

The connector supports adding rows using INSERT statements. By default, data insertion is performed by writing data to a temporary table. You can skip this step to improve performance and write directly to the target table. Set the insert.non-transactional-insert.enabled catalog property or the corresponding non_transactional_insert catalog session property to true.

Note that with this property enabled, data can be corrupted in rare cases where exceptions occur during the insert operation. With transactions disabled, no rollback can be performed.

Querying Phoenix tables#

The default empty schema in Phoenix maps to a schema named default in Trino. You can see the available Phoenix schemas by running SHOW SCHEMAS:

SHOW SCHEMAS FROM phoenix;

If you have a Phoenix schema named web, you can view the tables in this schema by running SHOW TABLES:

SHOW TABLES FROM phoenix.web;

You can see a list of the columns in the clicks table in the web schema using either of the following:

DESCRIBE phoenix.web.clicks;
SHOW COLUMNS FROM phoenix.web.clicks;

Finally, you can access the clicks table in the web schema:

SELECT * FROM phoenix.web.clicks;

If you used a different name for your catalog properties file, use that catalog name instead of phoenix in the above examples.

Type mapping#

Because Trino and Phoenix 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.

Phoenix type to Trino type mapping#

The connector maps Phoenix types to the corresponding Trino types following this table:

Phoenix type to Trino type mapping#
Phoenix database type	Trino type
`BOOLEAN`	`BOOLEAN`
`TINYINT`	`TINYINT`
`UNSIGNED_TINYINT`	`TINYINT`
`SMALLINT`	`SMALLINT`
`UNSIGNED_SMALLINT`	`SMALLINT`
`INTEGER`	`INTEGER`
`UNSIGNED_INT`	`INTEGER`
`BIGINT`	`BIGINT`
`UNSIGNED_LONG`	`BIGINT`
`FLOAT`	`REAL`
`UNSIGNED_FLOAT`	`REAL`
`DOUBLE`	`DOUBLE`
`UNSIGNED_DOUBLE`	`DOUBLE`
`DECIMAL(p,s)`	`DECIMAL(p,s)`
`CHAR(n)`	`CHAR(n)`
`VARCHAR(n)`	`VARCHAR(n)`
`BINARY`	`VARBINARY`
`VARBINARY`	`VARBINARY`
`DATE`	`DATE`
`UNSIGNED_DATE`	`DATE`
`ARRAY`	`ARRAY`

No other types are supported.

Trino type to Phoenix type mapping#

The Phoenix fixed length BINARY data type is mapped to the Trino variable length VARBINARY data type. There is no way to create a Phoenix table in Trino that uses the BINARY data type, as Trino does not have an equivalent type.

The connector maps Trino types to the corresponding Phoenix types following this table:

Trino type to Phoenix type mapping#
Trino database type	Phoenix type
`BOOLEAN`	`BOOLEAN`
`TINYINT`	`TINYINT`
`SMALLINT`	`SMALLINT`
`INTEGER`	`INTEGER`
`BIGINT`	`BIGINT`
`REAL`	`FLOAT`
`DOUBLE`	`DOUBLE`
`DECIMAL(p,s)`	`DECIMAL(p,s)`
`CHAR(n)`	`CHAR(n)`
`VARCHAR(n)`	`VARCHAR(n)`
`VARBINARY`	`VARBINARY`
`TIME`	`TIME`
`DATE`	`DATE`
`ARRAY`	`ARRAY`

No other types are supported.

Decimal type handling#

DECIMAL types with unspecified precision or scale are mapped to a Trino DECIMAL with a default precision of 38 and default scale of 0. The scale can be changed by setting the decimal-mapping configuration property or the decimal_mapping session property to allow_overflow. The scale of the resulting type is controlled via the decimal-default-scale configuration property or the decimal-rounding-mode session property. The precision is always 38.

By default, values that require rounding or truncation to fit will cause a failure at runtime. This behavior is controlled via the decimal-rounding-mode configuration property or the decimal_rounding_mode session property, which can be set to UNNECESSARY (the default), UP, DOWN, CEILING, FLOOR, HALF_UP, HALF_DOWN, or HALF_EVEN (see RoundingMode).

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

unsupported-type-handling

Configure how unsupported column data types are handled:

IGNORE, column is not accessible.
CONVERT_TO_VARCHAR, column is converted to unbounded VARCHAR.

The respective catalog session property is unsupported_type_handling.

IGNORE

jdbc-types-mapped-to-varchar

Allow forced mapping of comma separated lists of data types to convert to unbounded VARCHAR

Table properties - Phoenix#

Table property usage example:

CREATE TABLE myschema.scientists (
  recordkey VARCHAR,
  birthday DATE,
  name VARCHAR,
  age BIGINT
)
WITH (
  rowkeys = 'recordkey,birthday',
  salt_buckets = 10
);

The following are supported Phoenix table properties from https://phoenix.apache.org/language/index.html#options

Property name	Default value	Description
`rowkeys`	`ROWKEY`	Comma-separated list of primary key columns. See further description below
`split_on`	(none)	List of keys to presplit the table on. See Split Point.
`salt_buckets`	(none)	Number of salt buckets for this table.
`disable_wal`	false	Whether to disable WAL writes in HBase for this table.
`immutable_rows`	false	Declares whether this table has rows which are write-once, append-only.
`default_column_family`	`0`	Default column family name to use for this table.

`rowkeys`#

This is a comma-separated list of columns to be used as the table’s primary key. If not specified, a BIGINT primary key column named ROWKEY is generated , as well as a sequence with the same name as the table suffixed with _seq (i.e. <schema>.<table>_seq) , which is used to automatically populate the ROWKEY for each row during insertion.

Table properties - HBase#

The following are the supported HBase table properties that are passed through by Phoenix during table creation. Use them in the same way as above: in the WITH clause of the CREATE TABLE statement.

Property name	Default value	Description
`versions`	`1`	The maximum number of versions of each cell to keep.
`min_versions`	`0`	The minimum number of cell versions to keep.
`compression`	`NONE`	Compression algorithm to use. Valid values are `NONE` (default), `SNAPPY`, `LZO`, `LZ4`, or `GZ`.
`data_block_encoding`	`FAST_DIFF`	Block encoding algorithm to use. Valid values are: `NONE`, `PREFIX`, `DIFF`, `FAST_DIFF` (default), or `ROW_INDEX_V1`.
`ttl`	`FOREVER`	Time To Live for each cell.
`bloomfilter`	`NONE`	Bloomfilter to use. Valid values are `NONE` (default), `ROW`, or `ROWCOL`.

SQL support#

The connector provides read and write access to data and metadata in Phoenix. In addition to the globally available and read operation statements, the connector supports the following features:

SQL DELETE#

If a WHERE clause is specified, the DELETE operation only works if the predicate in the clause can be fully pushed down to the data source.