Class

org.apache.spark.sql.jdbc

JdbcDialect

Related Doc: package jdbc

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abstract class JdbcDialect extends Serializable

:: DeveloperApi :: Encapsulates everything (extensions, workarounds, quirks) to handle the SQL dialect of a certain database or jdbc driver. Lots of databases define types that aren't explicitly supported by the JDBC spec. Some JDBC drivers also report inaccurate information---for instance, BIT(n>1) being reported as a BIT type is quite common, even though BIT in JDBC is meant for single-bit values. Also, there does not appear to be a standard name for an unbounded string or binary type; we use BLOB and CLOB by default but override with database-specific alternatives when these are absent or do not behave correctly.

Currently, the only thing done by the dialect is type mapping. getCatalystType is used when reading from a JDBC table and getJDBCType is used when writing to a JDBC table. If getCatalystType returns null, the default type handling is used for the given JDBC type. Similarly, if getJDBCType returns (null, None), the default type handling is used for the given Catalyst type.

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@DeveloperApi() @Evolving()
Source
JdbcDialects.scala
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Instance Constructors

  1. new JdbcDialect()

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Abstract Value Members

  1. abstract def canHandle(url: String): Boolean

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    Check if this dialect instance can handle a certain jdbc url.

    Check if this dialect instance can handle a certain jdbc url.

    url

    the jdbc url.

    returns

    True if the dialect can be applied on the given jdbc url.

    Exceptions thrown

    NullPointerException if the url is null.

Concrete Value Members

  1. final def !=(arg0: Any): Boolean

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  2. final def ##(): Int

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  3. final def ==(arg0: Any): Boolean

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  4. final def asInstanceOf[T0]: T0

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  5. def beforeFetch(connection: Connection, properties: Map[String, String]): Unit

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    Override connection specific properties to run before a select is made.

    Override connection specific properties to run before a select is made. This is in place to allow dialects that need special treatment to optimize behavior.

    connection

    The connection object

    properties

    The connection properties. This is passed through from the relation.

  6. def clone(): AnyRef

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    protected[java.lang]
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    @throws( ... )
  7. def compileValue(value: Any): Any

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    Converts value to SQL expression.

    Converts value to SQL expression.

    value

    The value to be converted.

    returns

    Converted value.

    Annotations
    @Since( "2.3.0" )
  8. final def eq(arg0: AnyRef): Boolean

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  9. def equals(arg0: Any): Boolean

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  10. def escapeSql(value: String): String

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    Escape special characters in SQL string literals.

    Escape special characters in SQL string literals.

    value

    The string to be escaped.

    returns

    Escaped string.

    Attributes
    protected[org.apache.spark.sql.jdbc]
    Annotations
    @Since( "2.3.0" )
  11. def finalize(): Unit

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    @throws( classOf[java.lang.Throwable] )
  12. def getCatalystType(sqlType: Int, typeName: String, size: Int, md: MetadataBuilder): Option[DataType]

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    Get the custom datatype mapping for the given jdbc meta information.

    Get the custom datatype mapping for the given jdbc meta information.

    sqlType

    The sql type (see java.sql.Types)

    typeName

    The sql type name (e.g. "BIGINT UNSIGNED")

    size

    The size of the type.

    md

    Result metadata associated with this type.

    returns

    The actual DataType (subclasses of org.apache.spark.sql.types.DataType) or null if the default type mapping should be used.

  13. final def getClass(): Class[_]

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  14. def getJDBCType(dt: DataType): Option[JdbcType]

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    Retrieve the jdbc / sql type for a given datatype.

    Retrieve the jdbc / sql type for a given datatype.

    dt

    The datatype (e.g. org.apache.spark.sql.types.StringType)

    returns

    The new JdbcType if there is an override for this DataType

  15. def getSchemaQuery(table: String): String

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    The SQL query that should be used to discover the schema of a table.

    The SQL query that should be used to discover the schema of a table. It only needs to ensure that the result set has the same schema as the table, such as by calling "SELECT * ...". Dialects can override this method to return a query that works best in a particular database.

    table

    The name of the table.

    returns

    The SQL query to use for discovering the schema.

    Annotations
    @Since( "2.1.0" )
  16. def getTableExistsQuery(table: String): String

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    Get the SQL query that should be used to find if the given table exists.

    Get the SQL query that should be used to find if the given table exists. Dialects can override this method to return a query that works best in a particular database.

    table

    The name of the table.

    returns

    The SQL query to use for checking the table.

  17. def getTruncateQuery(table: String, cascade: Option[Boolean] = isCascadingTruncateTable): String

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    The SQL query that should be used to truncate a table.

    The SQL query that should be used to truncate a table. Dialects can override this method to return a query that is suitable for a particular database. For PostgreSQL, for instance, a different query is used to prevent "TRUNCATE" affecting other tables.

    table

    The table to truncate

    cascade

    Whether or not to cascade the truncation

    returns

    The SQL query to use for truncating a table

    Annotations
    @Since( "2.4.0" )
  18. def getTruncateQuery(table: String): String

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    The SQL query that should be used to truncate a table.

    The SQL query that should be used to truncate a table. Dialects can override this method to return a query that is suitable for a particular database. For PostgreSQL, for instance, a different query is used to prevent "TRUNCATE" affecting other tables.

    table

    The table to truncate

    returns

    The SQL query to use for truncating a table

    Annotations
    @Since( "2.3.0" )
  19. def hashCode(): Int

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  20. def isCascadingTruncateTable(): Option[Boolean]

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    Return Some[true] iff TRUNCATE TABLE causes cascading default.

    Return Some[true] iff TRUNCATE TABLE causes cascading default. Some[true] : TRUNCATE TABLE causes cascading. Some[false] : TRUNCATE TABLE does not cause cascading. None: The behavior of TRUNCATE TABLE is unknown (default).

  21. final def isInstanceOf[T0]: Boolean

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  22. final def ne(arg0: AnyRef): Boolean

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  23. final def notify(): Unit

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  24. final def notifyAll(): Unit

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  25. def quoteIdentifier(colName: String): String

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    Quotes the identifier.

    Quotes the identifier. This is used to put quotes around the identifier in case the column name is a reserved keyword, or in case it contains characters that require quotes (e.g. space).

  26. final def synchronized[T0](arg0: ⇒ T0): T0

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  27. def toString(): String

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  28. final def wait(): Unit

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    @throws( ... )
  29. final def wait(arg0: Long, arg1: Int): Unit

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  30. final def wait(arg0: Long): Unit

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