Filtering Data in Apache HBase using JAVA API

Published: 25 October 2022
on channel: Unboxing Big Data

1,473

FILTERING ROWS BASED ON A CONDITION.

FILTER ALLOWS US TO CONTROL WHAT DATA IS RETRIEVED BY SCAN

HBASE PROVIDES A LARGE NUMBER OF BUILT IN FILTERS

FILTER:
CAN RETURN SPECIFIC SET OF ROW IDs.
SPECIFIC SET OF COL/COL FAMILIES
TIMESTAMPS
SPECIFIC VALUE FOR A COL.
AND MANY MORE....

ALL FILTERS ARE SUBCLASSES OF FILTER ABSTRACT CLASS.

ROW FILTER : (CHECK IF ROW ID MATCHES SPECIFIED CONDITION)

ONE OF THE BUILT-IN FILTERS PROVIDED BY HBASE.

ROW FILTER DESCENDS FROM COMPARE FILTER.

FILTER (BASE CLASS) == FILTERBASE == COMPAREFILTER == ROWFILTER

COMPARE FILTER REQUIRES 2 PARAMETERS.

1. OPERATOR
2. COMPARATOR OBJECT

COMPAREFILTER CLASS PROVIDES FEW OPERATORS :

LESS,LESS_OR_EQUAL,EQUAL,NOT_EQUAL,GREATER_OR_EQUAL,GREATER

COMPARATOR OBJECT

THESE ARE THE OBJECTS WHICH WILL COMPARE THE TABLE DATA AGAINST A SPECIFIED VALUE

ROW FILTER WILL TAKE THE OPERATOR AND COMPARATOR OBJECT AND USE THEM TO FILTER ROW IDs

Filter filter = new RowFilter(CompareFilter.CompareOp.EQUAL,
new BinaryComparator(Bytes.toBytes("1")));

CompareFilter.CompareOp.EQUAL == operator
new BinaryComparator(Bytes.toBytes("1"))); == comparator object

//This filter will check if row id matches string "1"

OTHER COMPARATORS AVAILABLE LIKE (FOR COMPARING STRINGS)
REGEXSTRING
SUBSTRING

AT LAST PASS IT TO SET FILTER METHOD OF SCAN OBJECT

Scan userScan = new Scan();
userScan.setFilter(filter); //Scan objects have a setFilter method where we can specify a filter

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