Query efficiency using merged columns

A computer program product, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processing unit to cause the processing unit to:

• receive, from a host, a first query configured to perform a command on one or more target columns in a database;
• analyze a set of statistics for the database;
• determine, based on the analysis, a first column of the one or more target columns is included in a set of sparse columns;
• generate a plurality of access plans for the first query, including a first access plan that merges the first column with a second column;
• transform, based on the first access plan, the first query to merge the first column with the second column;
• and
• execute, in response to the transforming, the first query.

A system comprising:

• a processor;
• a database;
• and
• a computer-readable storage medium communicatively coupled to the processor and storing program instructions which, when executed by the processor, are configured to cause the processor to:
• analyze a set of database statistics to determine a hole rate and a data distribution for each column of a plurality of columns stored in the database;
• identify, from one or more target columns of a first query and based on the hole rate for each column, a set of sparse columns from the one or more target columns;
• estimate a computation cost for each access plan of a set of access plans, where a first access plan includes merging two or more columns into a merged column, wherein the merged column comprises a first sparse column and a second sparse column from the set of sparse columns;
• and
• transform, based on the first access plan having a lowest estimated computation cost, the first query to execute using the merged column.