We can now support richer set of queries in router planner.
This allow us to support CTEs, joins, window function, subqueries
if they are known to be executed at a single worker with a single
task (all tables are filtered down to a single shard and a single
worker contains all table shards referenced in the query).
Fixes : #501
Fixes#394
This change adds LIMIT/OFFSET support for non router-plannable
distributed queries.
In cases that we can push the LIMIT down, we add the OFFSET value to
that LIMIT in the worker queries. When a query with LIMIT x OFFSET y is issued,
the query is propagated to the workers as LIMIT (x+y) OFFSET 0, and on the
master table, the original LIMIT and OFFSET values are used. With this change,
we can use OFFSET wherever we can use LIMIT.
This change removes the whitelisting check on the WHERE clauses. Note that, before
this change, citus was already allowing all types of nodes with the following
format (i.e., wrap with a boolean test):
* SELECT col FROM table WHERE (ANY EXPRESSION) is TRUE;
Thus, this change is mostly useful for allowing the expressions in the WHERE clause
directly and avoiding "unsupport clause type" errors.
Murat Tuncer
Eren
Marco Slot
Andres Freund
Onder Kalaci
Jason Petersen