org.apache.metamodel.csv

Class CsvDataContext

java.lang.Object

org.apache.metamodel.AbstractDataContext

org.apache.metamodel.QueryPostprocessDataContext

org.apache.metamodel.csv.CsvDataContext

All Implemented Interfaces:

HasReadTypeConverters, DataContext, UpdateableDataContext

public final class CsvDataContext
extends QueryPostprocessDataContext
implements UpdateableDataContext

DataContext implementation for reading CSV files.

Field Summary

Fields inherited from class org.apache.metamodel.QueryPostprocessDataContext

INFORMATION_SCHEMA_NAME, SYSTEM_PROPERTY_CREATE_DEFAULT_TABLE_ALIAS

Constructor Summary

Constructors

Constructor and Description
CsvDataContext(File file) Constructs a CSV DataContext based on a file
CsvDataContext(File file, CsvConfiguration configuration) Constructs a CSV DataContext based on a file The file provided can be either existing or non-existing.
CsvDataContext(InputStream inputStream, CsvConfiguration configuration) Constructs a CSV DataContext based on an InputStream
CsvDataContext(Resource resource, CsvConfiguration configuration)
CsvDataContext(URL url, CsvConfiguration configuration) Constructs a CSV DataContext based on a URL

Method Summary

Modifier and Type	Method and Description
protected com.opencsv.CSVReader	createCsvReader(BufferedReader reader)
protected com.opencsv.CSVReader	createCsvReader(int skipLines)
protected Number	executeCountQuery(Table table, List<FilterItem> whereItems, boolean functionApproximationAllowed) Executes a simple count query, if possible.
UpdateSummary	executeUpdate(UpdateScript update) Submits an UpdateScript for execution on the DataContext.
CsvConfiguration	getConfiguration() Gets the CSV configuration used
protected org.apache.metamodel.csv.CsvSchema	getMainSchema()
protected String	getMainSchemaName()
Resource	getResource() Gets the resource that is being read from.
protected boolean	isWritable()
DataSet	materializeMainSchemaTable(Table table, List<Column> columns, int maxRows) Executes a simple one-table query against a table in the main schema of the subclasses of this class.

Methods inherited from class org.apache.metamodel.QueryPostprocessDataContext

addConverter, executePrimaryKeyLookupQuery, executeQuery, getDefaultSchemaName, getSchemaByNameInternal, getSchemaNamesInternal, isMainSchemaTable, isScalarFunctionMaterialized, materializeFromItem, materializeMainSchemaTable, materializeMainSchemaTable, materializeMainSchemaTableSelect, materializeTable

Methods inherited from class org.apache.metamodel.AbstractDataContext

compileQuery, executeQuery, executeQuery, getColumnByQualifiedLabel, getDefaultSchema, getSchemaByName, getSchemaNames, getSchemas, getTableByQualifiedLabel, isQualifiedPathDelim, onSchemaCacheRefreshed, parseQuery, query, refreshSchemas

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.metamodel.DataContext

compileQuery, executeQuery, executeQuery, executeQuery, getColumnByQualifiedLabel, getDefaultSchema, getSchemaByName, getSchemaNames, getSchemas, getTableByQualifiedLabel, parseQuery, query, refreshSchemas

Constructor Detail

CsvDataContext

public CsvDataContext(File file,
                      CsvConfiguration configuration)

Constructs a CSV DataContext based on a file The file provided can be either existing or non-existing. In the case of non-existing files, a file will be automatically created when a CREATE TABLE update is executed on the DataContext.

Parameters:

file -

configuration -

CsvDataContext

public CsvDataContext(Resource resource,
                      CsvConfiguration configuration)

CsvDataContext

public CsvDataContext(URL url,
                      CsvConfiguration configuration)

Constructs a CSV DataContext based on a URL

Parameters:

url -

configuration -

CsvDataContext

public CsvDataContext(File file)

Constructs a CSV DataContext based on a file

Parameters:

file -

CsvDataContext

public CsvDataContext(InputStream inputStream,
                      CsvConfiguration configuration)

Constructs a CSV DataContext based on an InputStream

Parameters:

inputStream -

configuration -

Method Detail

getConfiguration

public CsvConfiguration getConfiguration()

Gets the CSV configuration used

Returns:

a CSV configuration

getResource

public Resource getResource()

Gets the resource that is being read from.

Returns:

executeCountQuery

protected Number executeCountQuery(Table table,
                                   List<FilterItem> whereItems,
                                   boolean functionApproximationAllowed)

Description copied from class: QueryPostprocessDataContext

Executes a simple count query, if possible. This method is provided to allow subclasses to optimize count queries since they are quite common and often a datastore can retrieve the count using some specialized means which is much more performant than counting all records manually.

Overrides:

executeCountQuery in class QueryPostprocessDataContext

Parameters:

table - the table on which the count is requested.

whereItems - a (sometimes empty) list of WHERE items.

functionApproximationAllowed - whether approximation is allowed or not.

Returns:

the count of the particular table, or null if not available.

materializeMainSchemaTable

public DataSet materializeMainSchemaTable(Table table,
                                          List<Column> columns,
                                          int maxRows)

Description copied from class: QueryPostprocessDataContext

Executes a simple one-table query against a table in the main schema of the subclasses of this class.

Specified by:

materializeMainSchemaTable in class QueryPostprocessDataContext

Parameters:

table - the table to query

columns - the columns of the table to query

maxRows - the maximum amount of rows needed or -1 if all rows are wanted.

Returns:

a dataset with the raw table/column content.

createCsvReader

protected com.opencsv.CSVReader createCsvReader(int skipLines)

createCsvReader

protected com.opencsv.CSVReader createCsvReader(BufferedReader reader)

getMainSchema

protected org.apache.metamodel.csv.CsvSchema getMainSchema()
                                                    throws MetaModelException

Specified by:

getMainSchema in class QueryPostprocessDataContext

Returns:

the main schema that subclasses of this class produce

Throws:

MetaModelException

getMainSchemaName

protected String getMainSchemaName()

Specified by:

getMainSchemaName in class QueryPostprocessDataContext

Returns:

the name of the main schema that subclasses of this class produce

isWritable

protected boolean isWritable()

executeUpdate

public UpdateSummary executeUpdate(UpdateScript update)

Description copied from interface: UpdateableDataContext

Submits an UpdateScript for execution on the DataContext. Since implementations of the DataContext vary quite a lot, there is no golden rule as to how an update script will be executed. But the implementors should strive towards handling an UpdateScript as a single transactional change to the data store.

Specified by:

executeUpdate in interface UpdateableDataContext

Parameters:

update - the update script to execute

Returns:

a summary of the updates performed