Comments (2)
Unless you're doing a DISTINCT on the column being sharded specifically, wouldn't you have the problem of possibly merging duplicates for that column when the master assembles the return set?
from pg_shard.
Hey @wtfuzz,
First, as @gmcquillan mentioned, if you're doing a DISTINCT on a non-partition column, its possible that some of the shards contain overlapping values for some of the values.
So, what you suggest is not safe to apply, we may end up with wrong results.
For non-partition columns, I cannot see any solutions without pulling all the data to the master. However, for partition column DISTINCT queries, it is possible to push down the query.
But in the near future, we do not plan such a feature to add pg_shard. You can check CitusDB, which is more powerful in terms of SELECT queries.
Thanks for reaching us!
Onder
from pg_shard.
Related Issues (20)
- Allow IMMUTABLE functions in modification commands HOT 8
- Does pg_shard support user defined functions? HOT 3
- Does pg_shard encrypt the messages between nodes? HOT 3
- build issue HOT 2
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- Schema support incomplete? HOT 1
- Support RETURNING in modification commands HOT 3
- sync-metadata does not support quoted column names HOT 1
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- 1.2.1 build error against PostgreSQL 9.5 HOT 2
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from pg_shard.