Team Exasol
Team Exasol

Question

What is a replicated table and how can the replication border be modified?

Answer

  • Replicates are used "on-the-fly" for local joins if a table is "small" regarding the threshold.
  • A replicated table accesses data directly from other nodes' database memories and keeps a local copy in its own DBRAM.
  • If a replicated table is modified, only changed data is reloaded into database memories of other nodes.
  • Modified tables and subselects cannot be used with smart table replication. Table replication border does not apply to those.
     
  • 💡 Using large replicated tables might cause decreased performance. Queries with expensive table scans (filter expressions) or between / cross joins may fall into this category.

Replication border

A table will be joined by smart table replication if it has fewer or equal rows than the threshold below.
The replication borders can be modified through extra database parameters in the web interface:

-soft_replicationborder_in_numrows=<numrows> [default is 100000 rows]