net.sf.farrago.fennel
Class FennelUtil

java.lang.Object
  net.sf.farrago.fennel.FennelUtil

public abstract class FennelUtil
extends Object

Static utility methods related to Fennel storage. Historically, these methods were refactored from FennelRelUtil to remove their dependency on the Farrago query package.

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/fennel/FennelUtil.java#10 $

Author:

John Pham

Constructor Summary

FennelUtil()

Method Summary

static FennelTupleDescriptor	convertRowTypeToFennelTupleDesc(RelDataType rowType) Creates a FennelTupleDescriptor for a RelDataType which is a row.
static FennelStandardTypeDescriptor	convertSqlTypeToFennelType(RelDataType sqlType) Converts a SQL type to a Fennel type.

Methods inherited from class java.lang.Object

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

Constructor Detail

FennelUtil

public FennelUtil()

Method Detail

convertRowTypeToFennelTupleDesc

public static FennelTupleDescriptor convertRowTypeToFennelTupleDesc(RelDataType rowType)

Creates a FennelTupleDescriptor for a RelDataType which is a row.

Parameters:

rowType - row type descriptor

Returns:

generated tuple descriptor

convertSqlTypeToFennelType

public static FennelStandardTypeDescriptor convertSqlTypeToFennelType(RelDataType sqlType)

Converts a SQL type to a Fennel type.

The mapping is as follows:

SQL type	Fennel type	Comments
SqlTypeName.BOOLEAN	BOOL
SqlTypeName.TINYINT	INT_8
SqlTypeName.SMALLINT	INT_16
SqlTypeName.INTEGER	INT_32
SqlTypeName.DECIMAL(precision, scale)	INT_64	We use a scaled integer representation. For example, the DECIMAL(6, 2) value 1234.5 would be represented as an INT_32 value 123450 (which is 1234.5 10 ^ 2)
SqlTypeName.DATE	INT_64	Milliseconds since the epoch.
SqlTypeName.TIME	INT_64	Milliseconds since midnight.
SqlTypeName.TIMESTAMP	INT_64	Milliseconds since the epoch.
Timestamp with timezone		Not implemented. We will probably use a user-defined type consisting of a TIMESTAMP and a VARCHAR.
SqlTypeName.INTERVAL_DAY_TIME	INT_64	Not implemented. All types of day-time interval are represented in the same way: an integer milliseconds value. For example, INTERVAL '1' HOUR and INTERVAL '3600' MINUTE are both represented as 3,600,000. TBD: How to represent fractions of seconds smaller than a millisecond, for example, INTERVAL SECOND(6).
SqlTypeName.INTERVAL_YEAR_MONTH	INT_64	Not implemented. All types of year-month interval are represented in the same way: an integer value which holds the number of months. For example, INTERVAL '2' YEAR and INTERVAL '24' MONTH are both represented as 24.
SqlTypeName.BIGINT	INT_64
SqlTypeName.VARCHAR(precision)	VARCHAR or UNICODE_VARCHAR depending on character set
SqlTypeName.VARBINARY(precision)	VARBINARY
SqlTypeName.MULTISET	VARBINARY	The fields are serialized into the VARBINARY field in the standard Fennel serialization format. There is no 'count' field. To deduce the number of records, deserialize values until you reach the length of the field. Of course, this requires that every value takes at least one byte. The length of a multiset value is limited by the capacity of the VARBINARY datatype. This limitation will be lifted when LONG VARBINARY is implemented.
SqlTypeName.ROW		The fields are 'flattened' so that they become top-level fields of the relation. If the row is nullable, then all fields will be nullable after flattening. An extra 'null indicator' field is added to discriminate between a NULL row and a not-NULL row which happens to have all fields NULL.
SqlTypeName.CHAR(precision)	CHAR or CHAR depending on character set
SqlTypeName.BINARY(precision)	BINARY
SqlTypeName.REAL	REAL
SqlTypeName.FLOAT	DOUBLE
SqlTypeName.DOUBLE	DOUBLE