Julian Hyde created CALCITE-689:
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Summary: Add filter, to allow a materialized view to ignore
invalid data
Key: CALCITE-689
URL: https://issues.apache.org/jira/browse/CALCITE-689
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
Assignee: Julian Hyde
A materialized view is a table that contains the result of executing a
particular query. But what if the table contains extra rows?
We propose to add a filter -- a RexNode condition, or a SQL WHERE clause --
that Calcite would apply whenever the materialized view was used.
One use case this would allow: invalidating parts of an MV, as their underlying
data is modified, without invalidating the whole MV. Suppose that the
materialized view covers sales to states CA, OR, WA in years 2013, 2014:
{code}sql: SELECT state, year, SUM(units) FROM sales WHERE state IN ('CA',
'OR', 'WA') AND year IN (2013, 2014) GROUP BY state, year{code}
Now suppose that one record in (CA, 2013) is modified. We don't want to
re-create the MV. We can change the definition of the MV as follows:
{code}sql: SELECT state, year, SUM(units) FROM sales WHERE state IN ('OR',
'WA') AND year IN (2013, 2014) GROUP BY state, year
filter: state != 'CA'{code}
We have narrowed the set of cells that the MV claims to provide, and we have
provided a filter to remove extra data. The filter makes it clear that the MV
contains extra rows; some uses might decide they don't need the filter.
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