Bulk Unload/extract (prototype) These changes add support for a bulk unload/extract (prototype) to unload data from trafodion tables into HDFS. Bulk unload unloads data in either compressed (gzip) or uncompressed formats. When specified, compression take place before writing data bufers to files. Once the data unloading is done the files are merged into one single file. If compression is specified the data are unloaded into files in compressed format and then merged in compressed format. Otherwise they are unloaded in uncompressed format and merged into one uncompressed file.
The unload syntax is:
UNLOAD [[WITH option] [, option] ...] INTO <hive-table> query_expression
Where *<hive-table> is a hive table. and *option can be: - PURGEDATA FROM TARGET: When this option specfied the files under the <hive-table> are deleted - COMPRESSION GZIP: when this option is specfied the Gzip compression is used. the compression takes place in the hive-insert node and data is written to disk in compressed format (Gzip i the only supported compression for now) - MERGE FILE <merged_file-path>: When this option is specified the files unloaded are merged into one single file <merged-file-path>. if compressiion is specied the data unloaded in compressed format and the merged file will be in compressed formt also. - NO OUTPUT: If this option is specified then no status messge is dispalyed