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Creating/Viewing Scrambles

A scramble is a special table used by VerdictDB to speed up query processing. The information about the created scrambles is stored in its metadata table and is used at query time.

Syntax for Creating Scrambles

CREATE SCRAMBLE newSchema.newTable FROM originalSchema.originalTable [SIZE sizeOfScramble] [BLOCKSIZE sizeOfBlock];

Note:

  1. newSchema may be identical to originalSchema.
  2. newTable must be different from originalTable if newSchema is same as originalSchema.
  3. The user requires the write privilege for the newSchema schema and the read privilege for the originalSchema.originalTable.
  4. sizeOfScramble (default = 1.0) defines the relative size of the scramble to its original table and must be a float value between 0.0 and 1.0 (e.g., sizeOfScramble=0.1 will create a scramble which size is 10% of the original table).
  5. VerdictDB stores scrambles in a partitioned table and sizeOfBlock (default = 1,000,000 = 1M) specifies the number of records in each partition. However, the maximum number of partitions for scrambles is 100 by default, and sizeOfBlock will be adjusted automatically by VerdictDB if the specified sizeOfBlock results in more than 100 partitions.
  6. The schema and table names can be quoted either using the double-quote (") or the backtick (`).
  7. The schema names, table names, column names, etc. in the queries issued by VerdictDB to the backend database are always quoted.

Syntax for Viewing Scrambles

SHOW SCRAMBLES;

This query will print the list of all scrambled tables that have been built.