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The following page has been changed by udanax: http://wiki.apache.org/hadoop/Hbase/HbaseShell/HQL ------------------------------------------------------------------------------ DataType value = rs.getValue("datatype"); } }}} + + == External HQL Query file == + HQL Query file is used for construct schema, table, and column references. It also created using table dump, and can be fed into Hbase to re-create the tables. + + {{{ + hql > load query file 'hdfs://hbase/script.hql'; + }}} + == Parallel Execution Features == === Parallel Query === Parallel execution can significantly reduce the elapsed time for large queries, but it doesn't apply to every query. {{{ - hql > alter table tbl_name parallel(map 4 reduce 1); + hql > alter table tbl_name parallel(map 4 reduce 1); - hql > select count(*) from tbl_name; + hql > select count(*) from tbl_name; - hql > alter table tbl_name noparallel; + hql > alter table tbl_name noparallel; }}} === Parallel Data Loading === HQL Loader utility loads data into Hbase tables from external files. If you have a large amount of data to load, HQL Loader's parallel support can dramatically reduce the elapsed time needed to perform that load. {{{ - hql > load data file 'hdfs://hbase/big.dat' + hql > load data file 'hdfs://hbase/big.dat' - --> into table tbl_name + --> into table tbl_name - --> fields terminated by '\t' + --> fields terminated by '\t' - --> lines terminated by '\n' + --> lines terminated by '\n' - --> (column1[, column2, ...]); + --> (column1[, column2, ...]); }}}
