[ https://issues.apache.org/jira/browse/TRAFODION-1419?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Work on TRAFODION-1419 started by Anoop Sharma. ----------------------------------------------- > Add support for multiple column families in a trafodion table > ------------------------------------------------------------- > > Key: TRAFODION-1419 > URL: https://issues.apache.org/jira/browse/TRAFODION-1419 > Project: Apache Trafodion > Issue Type: New Feature > Reporter: Anoop Sharma > Assignee: Anoop Sharma > > This proposal is to add support for multiple column families in trafodion > tables. With this feature, one can store columns into multiple column > families. One use for this would be to store frequently used columns in one > column family and infrequently used columns to be stored in a different > column family. That will have performance improvement when those columns are > retrieved from hbase. There could be other uses as well. > Syntax: > create table <tablename> ( <colFam1>.<colName1> <datatype>, > <colFam2>.<colName2> <datatype> ….) > attributes default column family <colFam>; > alter table <tablename> add column <colFam>.<colName> datatype; > <colFam> : name of column family for that column > Semantics: > <colFam> name follows identifier rules. If not double quoted, then it > will be upper cased. If double quoted, then case will be maintained. > User specified column family can be of arbitrary length. To optimize > space for column family stored in a cell, a 2 byte encoding is generated. > Mapping of user specified column family to encoded column family is stored in > metadata. > If no column family is specified for a column during create table, then > the family specified in ‘attributes default column family’ clause is used. > If no ‘attribute default column family’ clause is specified , then system > default col family is used. > column family specification is supported for regular and volatile > tables. > all unique column families specified during create or alter are added > to the table > maximum number of column families supported in one table is 32. But it > is hbase recommendation to not create too many column families. > alter statement can be used to assign specific hbase options to > specific column families > using the NAME clause. If no name clause is specified, then alter hbase > options are applied > to all col families. > invoke and showddl statements will show the original user specified > column families and not the encoded column families > Currently, multiple column families are not supported for columns of a > user created or an implicitly created index. > The default column family of the corresponding base table is used for all > index columns. > column family cannot be specified in a DML query > column family cannot be specified for columns of an aligned row format > table since all columns are stored as one cell > Column names must be unique for each table. The same column name cannot > be used as part of multiple column families. -- This message was sent by Atlassian JIRA (v6.3.4#6332)