Oracle connector

Zipstack Cloud features a powerful SQL querying engine on top of many types of connectors, including those from Trino, some custom connectors and connectors from the open source Airbyte project. The underlying native connectors are Trino's connectors. Additionally, some parts of the documentation for these connectors have been adapted from the connector documentation found in Trino's open source project.

info

Please reach out to [email protected] if you need Oracle with keystore based authentication. This requires provisioning Zipstack Cloud with extra modules/properties.

The Oracle connector allows querying and creating tables in an external Oracle database. Connectors let Trino join data provided by different databases, like Oracle and Hive, or different Oracle database instances.

Requirements

To connect to Oracle, you need:

• Oracle 12 or higher.

• Network access from Zipstack Cloud to Oracle. Port 1521 is the default port.

Configuration

To configure the Oracle connector create a data source with type Oracle. Include the following minimum properties in the file:

# The correct syntax of the connection-url varies by Oracle version and
# configuration. The following example URL connects to an Oracle SID named
# "orcl".
connection-url=jdbc:oracle:thin:@example.net:1521:orcl
connection-user=root
connection-password=secret

The connection-url defines the connection information and parameters to pass to the JDBC driver. The Oracle connector uses the Oracle JDBC Thin driver, and the syntax of the URL may be different depending on your Oracle configuration. For example, the connection URL is different if you are connecting to an Oracle SID or an Oracle service name. See the Oracle Database JDBC driver documentation for more information.

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 </security/secrets> to avoid actual values in the catalog properties files.

::: note ::: title Note :::

Oracle does not expose metadata comment via REMARKS column by default in JDBC driver. You can enable it using remarks-reporting.enabled config option. See Additional Oracle Performance Extensions for more details. :::

By default, the Oracle connector uses connection pooling for performance improvement. The below configuration shows the typical default values. To update them, change the properties in the catalog configuration file:

connection-pool.max-size=30
connection-pool.min-size=1
connection-pool.inactive-timeout=20m

To disable connection pooling, update properties to include the following:

connection-pool.enabled=false

Data source authentication

The connector can provide credentials for the data source connection in multiple ways:

• inline, in the connector configuration file

• in a separate properties file

• in a key store file

• as extra credentials set when connecting to Trino

You can use secrets </security/secrets> to avoid storing sensitive values in the catalog properties files.

The following table describes configuration properties for connection credentials:

Property name	Description
credential-provider.type	Type of the credential provider. Must be one of INLINE, FILE, or KEYSTORE; defaults to INLINE.
connection-user	Connection user name.
connection-password	Connection password.
user-credential-name	Name of the extra credentials property, whose value to use as the user name. See extraCredentials in Parameter reference.
password-credential-name	Name of the extra credentials property, whose value to use as the password.
connection-credential-file	Location of the properties file where credentials are present. It must contain the connection-user and connection-password properties.
keystore-file-path	The location of the Java Keystore file, from which to read credentials.
keystore-type	File format of the keystore file, for example JKS or PEM.
keystore-password	Password for the key store.
keystore-user-credential-name	Name of the key store entity to use as the user name.
keystore-user-credential-password	Password for the user name key store entity.
keystore-password-credential-name	Name of the key store entity to use as the password.
keystore-password-credential-password	Password for the password key store entity.

Multiple Oracle servers

If you want to connect to multiple Oracle servers, configure another instance of the Oracle connector as a separate catalog.

To add another Oracle catalog, create a new properties file. For example, if you name the property file sales.properties, Trino creates a catalog named sales.

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	This value should be a duration.	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. This value should be a duration.	(refresh disabled)
metadata.cache-ttl	The duration for which metadata, including table and column statistics, is cached.	0s (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 </admin/dynamic-filtering>. The domain-compaction-threshold catalog configuration property or the domain_compaction_threshold catalog session property <session-properties-definition> can be used to adjust the default value of 32 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.example_schema;
  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 </sql/insert>. 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 Oracle

The Oracle connector provides a schema for every Oracle database.

Run SHOW SCHEMAS to see the available Oracle databases:

SHOW SCHEMAS FROM example;

If you used a different name for your catalog properties file, use that catalog name instead of example.

note

The Oracle user must have access to the table in order to access it from Trino. The user configuration, in the connection properties file, determines your privileges in these schemas.

Examples

If you have an Oracle database named web, run SHOW TABLES to see the tables it contains:

SHOW TABLES FROM example.web;

To see a list of the columns in the clicks table in the web database, run either of the following:

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

To access the clicks table in the web database, run the following:

SELECT * FROM example.web.clicks;

Type mapping

Because Trino and Oracle each support types that the other does not, this connector modifies some types <type-mapping-overview> 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.

Oracle to Trino type mapping

Trino supports selecting Oracle database types. This table shows the Oracle to Trino data type mapping:

Oracle database type	Trino type	Notes
NUMBER(p, s)	DECIMAL(p, s)	See Mapping numeric types
NUMBER(p)	DECIMAL(p, 0)	See Mapping numeric types
FLOAT[(p)]	DOUBLE
BINARY_FLOAT	REAL
BINARY_DOUBLE	DOUBLE
VARCHAR2(n CHAR)	VARCHAR(n)
VARCHAR2(n BYTE)	VARCHAR(n)
NVARCHAR2(n)	VARCHAR(n)
CHAR(n)	CHAR(n)
NCHAR(n)	CHAR(n)
CLOB	VARCHAR
NCLOB	VARCHAR
RAW(n)	VARBINARY
BLOB	VARBINARY
DATE	TIMESTAMP(0)	See Mapping datetime types
TIMESTAMP(p)	TIMESTAMP	See Mapping datetime types
TIMESTAMP(p) WITH TIME ZONE	TIMESTAMP WITH TIME ZONE	See Mapping datetime types

No other types are supported.

Trino to Oracle type mapping

Trino supports creating tables with the following types in an Oracle database. The table shows the mappings from Trino to Oracle data types:

note

For types not listed in the table below, Trino can't perform the CREATE TABLE <table> AS SELECT operations. When data is inserted into existing tables, Oracle to Trino type mapping is used.

Trino type	Oracle database type	Notes
TINYINT	NUMBER(3)
SMALLINT	NUMBER(5)
INTEGER	NUMBER(10)
BIGINT	NUMBER(19)
DECIMAL(p, s)	NUMBER(p, s)
REAL	BINARY_FLOAT
DOUBLE	BINARY_DOUBLE
VARCHAR	NCLOB
VARCHAR(n)	VARCHAR2(n CHAR) or NCLOB	See Mapping character types
CHAR(n)	CHAR(n CHAR) or NCLOB	See Mapping character types
VARBINARY	BLOB
DATE	DATE	See Mapping datetime types
TIMESTAMP	TIMESTAMP(3)	See Mapping datetime types
TIMESTAMP WITH TIME ZONE	TIMESTAMP(3) WITH TIME ZONE	See Mapping datetime types

No other types are supported.

An Oracle NUMBER(p, s) maps to Trino's DECIMAL(p, s) except in these conditions:

• No precision is specified for the column (example: NUMBER or NUMBER(*)), unless number.default-scale is set.

• Scale (s ) is greater than precision.

• Precision (p ) is greater than 38.

• Scale is negative and the difference between p and s is greater than 38, unless number.rounding-mode is set to a different value than UNNECESSARY.

If s is negative, NUMBER(p, s) maps to DECIMAL(p + s, 0).

For Oracle NUMBER (without precision and scale), you can change number.default-scale=s and map the column to DECIMAL(38, s).

Selecting a timestamp with fractional second precision (p) greater than 3 truncates the fractional seconds to three digits instead of rounding it.

Oracle DATE type stores hours, minutes, and seconds, so it is mapped to Trino TIMESTAMP(0).

caution

Due to date and time differences in the libraries used by Trino and the Oracle JDBC driver, attempting to insert or select a datetime value earlier than 1582-10-15 results in an incorrect date inserted.

Trino's VARCHAR(n) maps to VARCHAR2(n CHAR) if n is no greater than 4000. A larger or unbounded VARCHAR maps to NCLOB.

Trino's CHAR(n) maps to CHAR(n CHAR) if n is no greater than 2000. A larger CHAR maps to NCLOB.

Using CREATE TABLE AS to create an NCLOB column from a CHAR value removes the trailing spaces from the initial values for the column. Inserting CHAR values into existing NCLOB columns keeps the trailing spaces. For example:

CREATE TABLE vals AS SELECT CAST('A' as CHAR(2001)) col;
INSERT INTO vals (col) VALUES (CAST('BB' as CHAR(2001)));
SELECT LENGTH(col) FROM vals;

_col0

 2001
    1
(2 rows)

Attempting to write a CHAR that doesn’t fit in the column’s actual size fails. This is also true for the equivalent VARCHAR types.

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

Number to decimal configuration properties

Configuration property name	Session property name	Description	Default
number.default-scale	number_default_scale	Default Trino DECIMAL scale for Oracle NUMBER (without precision and scale) date type. When not set then such column is treated as not supported.	not set
number.rounding-mode	number_rounding_mode	Rounding mode for the Oracle NUMBER data type. This is useful when Oracle NUMBER data type specifies higher scale than is supported in Trino. Possible values are:UNNECESSARY - Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary.CEILING - Rounding mode to round towards positive infinity.FLOOR - Rounding mode to round towards negative infinity.HALF_DOWN - Rounding mode to round towards nearest neighbor unless both neighbors are equidistant, in which case rounding down is used.HALF_EVEN - Rounding mode to round towards the nearest neighbor unless both neighbors are equidistant, in which case rounding towards the even neighbor is performed.HALF_UP - Rounding mode to round towards nearest neighbor unless both neighbors are equidistant, in which case rounding up is usedUP - Rounding mode to round towards zero.DOWN - Rounding mode to round towards zero.	UNNECESSARY

SQL support

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

• INSERT
• DELETE
• TRUNCATE
• CREATE TABLE
• CREATE TABLE AS
• DROP TABLE
• ALTER TABLE
• COMMENT

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.

ALTER TABLE

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 Oracle.

query(varchar) -> table

The query function allows you to query the underlying database directly. It requires syntax native to Oracle, because the full query is pushed down and processed in Oracle. 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.

Note

Polymorphic table functions may not preserve the order of the query result. If the table function contains a query with an ORDER BY clause, the function result may not be ordered as expected.

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

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

As a practical example, you can use the MODEL clause from Oracle SQL:

SELECT
  SUBSTR(country, 1, 20) country,
  SUBSTR(product, 1, 15) product,
  year,
  sales
FROM
  TABLE(
    example.system.query(
      query => 'SELECT
        *
      FROM
        sales_view
      MODEL
        RETURN UPDATED ROWS
        MAIN
          simple_model
        PARTITION BY
          country
        MEASURES
          sales
        RULES
          (sales['Bounce', 2001] = 1000,
          sales['Bounce', 2002] = sales['Bounce', 2001] + sales['Bounce', 2000],
          sales['Y Box', 2002] = sales['Y Box', 2001])
      ORDER BY
        country'
    )
  );

Performance

The connector includes a number of performance improvements, detailed in the following sections.

Synonyms

Based on performance reasons, Trino disables support for Oracle SYNONYM. To include SYNONYM, add the following configuration property:

synonyms.enabled=true

Pushdown

The connector supports pushdown for a number of operations:

• Join pushdown
• Limit pushdown
• Top-N pushdown

In addition, the connector supports Aggregation pushdown for the following functions:

• avg()
• count(), also count(distinct x)
• max()
• min()
• sum()

Pushdown is only supported for DOUBLE type columns with the following functions:

• stddev() and stddev_samp()
• stddev_pop()
• var_pop()
• variance() and var_samp()

Pushdown is only supported for REAL or DOUBLE type column with the following functions:

• covar_samp()
• covar_pop()

Note

The connector performs pushdown where performance may be improved, but in order to preserve correctness an operation may not be pushed down. When pushdown of an operation may result in better performance but risks correctness, the connector prioritizes correctness.

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.

Predicate pushdown support

The connector does not support pushdown of any predicates on columns that use the CLOB, NCLOB, BLOB, or RAW(n) Oracle database types, or Trino data types that map to these Oracle database types.

In the following example, the predicate is not pushed down for either query since name is a column of type VARCHAR, which maps to NCLOB in Oracle:

SHOW CREATE TABLE nation;

--             Create Table
----------------------------------------
-- CREATE TABLE oracle.trino_test.nation (
--    name varchar
-- )
-- (1 row)

SELECT * FROM nation WHERE name > 'CANADA';
SELECT * FROM nation WHERE name = 'CANADA';

In the following example, the predicate is pushed down for both queries since name is a column of type VARCHAR(25), which maps to VARCHAR2(25) in Oracle:

SHOW CREATE TABLE nation;

--             Create Table
----------------------------------------
-- CREATE TABLE oracle.trino_test.nation (
--    name varchar(25)
-- )
-- (1 row)

SELECT * FROM nation WHERE name > 'CANADA';
SELECT * FROM nation WHERE name = 'CANADA';