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https://issues.apache.org/jira/browse/CALCITE-429?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jacques Nadeau closed CALCITE-429.
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Resolved in release 1.4.0-incubating (2015-08-23)
> Add statistics SPI for lattice optimization algorithm
> -----------------------------------------------------
>
> Key: CALCITE-429
> URL: https://issues.apache.org/jira/browse/CALCITE-429
> Project: Calcite
> Issue Type: New Feature
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Fix For: 1.4.0-incubating
>
>
> In OPTIQ-427 we added an an optimization algorithm to choose an initial set
> of tiles to materialize. The {{rowCountEstimate}} attribute is the number of
> rows in the lattice.
> Add an SPI to generate estimates of (a) the number of rows in the lattice,
> (b) the number of rows in a given tile of the lattice (specified by its
> dimensions).
> Also add a default implementation of the SPI that executes SQL queries,
> caches the results, and uses some kind of approximation for the cardinalities
> of sets of attributes e.g. if quarter has 4 distinct values and year has 10
> distinct values then (year, quarter) has 40 distinct values (or perhaps an
> expectation of 39.79 distinct values in a table with 3,650 rows, per the
> formula {{n . (1 - ((n - 1) / n) ^ p)}}).
> Implementations that read stats from external stats tables, or execute SQL
> that samples a small percentage of the rows, would also be possible.
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