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For the schema introspection, a simple query of the form SELECT * FROM {table} TABLESAMPLE SYSTEM (1) LIMIT 1 is used to get data samples. This doesn't work for all tables since some tables with partitions, for example, require that a WHERE clause is added based on the partition to narrow down the data scanned.
One proposal for handling this is to add it to the data source admin table as a column that can be modified to add a custom sample query
The text was updated successfully, but these errors were encountered:
Discussion here about how to handle getting samples for partitioned tables: mozilla/redash-stmo#53
In this case, we won't need to have this "custom queries" feature but just to handle queries for partitioned tables.
emtwo
changed the title
Allow custom queries to be added and used for gathering data samples
Allow data samples to be gathered for partitioned tables.
Sep 23, 2019
For the schema introspection, a simple query of the form
SELECT * FROM {table} TABLESAMPLE SYSTEM (1) LIMIT 1
is used to get data samples. This doesn't work for all tables since some tables with partitions, for example, require that aWHERE
clause is added based on the partition to narrow down the data scanned.One proposal for handling this is to add it to the data source admin table as a column that can be modified to add a custom sample query
The text was updated successfully, but these errors were encountered: