Package com.exasol.adapter.dialects.rewriting

Class AbstractQueryRewriter

java.lang.Object

com.exasol.adapter.dialects.rewriting.AbstractQueryRewriter

All Implemented Interfaces:

QueryRewriter

Direct Known Subclasses:

ImportFromJDBCQueryRewriter, ImportIntoTemporaryTableQueryRewriter

public abstract class AbstractQueryRewriter
extends Object
implements QueryRewriter

Abstract implementation of QueryRewriter.

Field Summary

Fields

Modifier and Type	Field	Description
protected ConnectionDefinitionBuilder	connectionDefinitionBuilder	Connection definition builder
protected SqlDialect	dialect	Dialect implementation
protected RemoteMetadataReader	remoteMetadataReader	Remote metadata reader

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractQueryRewriter(SqlDialect dialect, RemoteMetadataReader remoteMetadataReader, ConnectionDefinitionBuilder connectionDefinitionBuilder)	Create a new instance of a AbstractQueryRewriter.

Method Summary

Modifier and Type	Method	Description
protected abstract String	generateImportStatement(String connectionDefinition, String pushdownQuery)	Generate an IMPORT statement to be executed in the Exasol database, using the passed pushdown query to be executed in the external source be as source data.
protected String	generateImportStatement(String connectionDefinition, List<com.exasol.adapter.metadata.DataType> selectListDataTypes, String pushdownQuery)	This method provides backwards compatibility.
protected com.exasol.ExaConnectionInformation	getConnectionInformation(com.exasol.ExaMetadata exaMetadata, com.exasol.adapter.AdapterProperties properties)	Read the connection information from the metadata.
String	rewrite(com.exasol.adapter.sql.SqlStatement statement, List<com.exasol.adapter.metadata.DataType> selectListDataTypes, com.exasol.ExaMetadata exaMetadata, com.exasol.adapter.AdapterProperties properties)	Set the original push-down statement.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

dialect

protected final SqlDialect dialect

Dialect implementation

remoteMetadataReader

protected final RemoteMetadataReader remoteMetadataReader

Remote metadata reader

connectionDefinitionBuilder

protected final ConnectionDefinitionBuilder connectionDefinitionBuilder

Connection definition builder

Constructor Detail

AbstractQueryRewriter

protected AbstractQueryRewriter(SqlDialect dialect,
                                RemoteMetadataReader remoteMetadataReader,
                                ConnectionDefinitionBuilder connectionDefinitionBuilder)

Create a new instance of a AbstractQueryRewriter.

Parameters:

dialect - dialect

remoteMetadataReader - remote metadata reader

connectionDefinitionBuilder - builder for creating connection definitions

Method Detail

rewrite

public String rewrite(com.exasol.adapter.sql.SqlStatement statement,
                      List<com.exasol.adapter.metadata.DataType> selectListDataTypes,
                      com.exasol.ExaMetadata exaMetadata,
                      com.exasol.adapter.AdapterProperties properties)
               throws com.exasol.adapter.AdapterException,
                      SQLException

Description copied from interface: QueryRewriter

Set the original push-down statement.

Specified by:

rewrite in interface QueryRewriter

Parameters:

statement - SQL statement that represents the original push-down query

selectListDataTypes - expected data types of result set

exaMetadata - Exasol metadata

properties - user-defined adapter properties

Returns:

rewritten query

Throws:

com.exasol.adapter.AdapterException - if rewriting fails

SQLException - if any SQL commands executed on the remote data source failed during rewriting

getConnectionInformation

protected com.exasol.ExaConnectionInformation getConnectionInformation(com.exasol.ExaMetadata exaMetadata,
                                                                       com.exasol.adapter.AdapterProperties properties)
                                                                throws com.exasol.adapter.AdapterException

Read the connection information from the metadata.

Parameters:

exaMetadata - metadata

properties - adapter properties

Returns:

connection information

Throws:

com.exasol.adapter.AdapterException - if access fails

generateImportStatement

protected String generateImportStatement(String connectionDefinition,
                                         List<com.exasol.adapter.metadata.DataType> selectListDataTypes,
                                         String pushdownQuery)
                                  throws SQLException

This method provides backwards compatibility. A class extending the AbstractQueryRewriter has two options:

• Option (O1): override the new method generateImportStatement(String, List, String) enabling to use the new parameter selectListDataTypes to determine the data types of the result set of the query.
• Option (O2): only override the old method generateImportStatement(String, String) and by that falling back to the old way, i.e. inferring the data types of the result set by inspecting its values.

Parameters:

connectionDefinition - connection definition to be used when connecting to the external source

selectListDataTypes - expected data types of result set

pushdownQuery - source data for the `IMPORT...FROM` statement

Returns:

IMPORT statement to be executed on the Exasol database

Throws:

SQLException - if any problem occurs

generateImportStatement

protected abstract String generateImportStatement(String connectionDefinition,
                                                  String pushdownQuery)
                                           throws SQLException

Generate an IMPORT statement to be executed in the Exasol database, using the passed pushdown query to be executed in the external source be as source data.

Parameters:

connectionDefinition - connection definition to be used when connecting to the external source

pushdownQuery - source data for the `IMPORT...FROM` statement

Returns:

IMPORT statement to be executed on the Exasol database

Throws:

SQLException - if any problem occurs