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https://issues.apache.org/jira/browse/CALCITE-5281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17602551#comment-17602551
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Julian Hyde commented on CALCITE-5281:
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The relational algebra approach allows gains of efficiency when you are able to
push relational operations such as projects, filters, and sorts towards the
leaves of the tree. So, spatial functions that produce or consume relations (or
collections that could be treated as relations) are very much of interest. It
might be useful to keep a list of functions into which relational operations
could be pushed.
The other category of interactions between relational operators and spatial
functions is predicates and sorting/locality. For instance, {{ST_DWithin}} can
be converted to a range scan of a table of points or tiles ordered by a
space-filling curve because of the correlation between its input (geometry) and
output (boolean). All functions of that nature can be optimized by algebraic
rewrites.
> Implement geometry set returning functions (SRF)
> ------------------------------------------------
>
> Key: CALCITE-5281
> URL: https://issues.apache.org/jira/browse/CALCITE-5281
> Project: Calcite
> Issue Type: Improvement
> Components: spatial
> Reporter: Bertil Chapuis
> Assignee: Bertil Chapuis
> Priority: Minor
>
> The idea is to implement set returning functions, such as ST_Explode in H2GIS
> and ST_Dump in PostGIS. Is the Uncollect class a good starting point?
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