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()
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- JdbcDialect
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Instance Constructors
- new JdbcDialect()
Abstract Value Members
-
abstract
def
canHandle(url: String): Boolean
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
-
final
def
!=(arg0: Any): Boolean
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final
def
##(): Int
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final
def
==(arg0: Any): Boolean
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final
def
asInstanceOf[T0]: T0
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def
beforeFetch(connection: Connection, properties: Map[String, String]): Unit
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.
-
def
clone(): AnyRef
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- protected[java.lang]
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- @native() @throws( ... )
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def
compileValue(value: Any): Any
Converts value to SQL expression.
Converts value to SQL expression.
- value
The value to be converted.
- returns
Converted value.
- Annotations
- @Since( "2.3.0" )
-
final
def
eq(arg0: AnyRef): Boolean
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def
equals(arg0: Any): Boolean
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-
def
escapeSql(value: String): String
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" )
-
def
finalize(): Unit
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- protected[java.lang]
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def
getCatalystType(sqlType: Int, typeName: String, size: Int, md: MetadataBuilder): Option[DataType]
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.
-
final
def
getClass(): Class[_]
- Definition Classes
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- @native()
-
def
getJDBCType(dt: DataType): Option[JdbcType]
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
-
def
getSchemaQuery(table: String): String
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" )
-
def
getTableExistsQuery(table: String): String
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.
-
def
getTruncateQuery(table: String, cascade: Option[Boolean] = isCascadingTruncateTable): String
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" )
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def
getTruncateQuery(table: String): String
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" )
-
def
hashCode(): Int
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- @native()
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def
isCascadingTruncateTable(): Option[Boolean]
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). -
final
def
isInstanceOf[T0]: Boolean
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final
def
ne(arg0: AnyRef): Boolean
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final
def
notify(): Unit
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final
def
notifyAll(): Unit
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def
quoteIdentifier(colName: String): String
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).
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final
def
synchronized[T0](arg0: ⇒ T0): T0
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def
toString(): String
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def
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def
wait(arg0: Long, arg1: Int): Unit
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wait(arg0: Long): Unit
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