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https://issues.apache.org/jira/browse/CALCITE-1018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15052048#comment-15052048
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Maryann Xue commented on CALCITE-1018:
--------------------------------------
Any thoughts, [~julianhyde], [~jcamachorodriguez], [~pxiong]?
> SortJoinTransposeRule not firing due to getMaxRowCount(RelSubset) returning
> null
> --------------------------------------------------------------------------------
>
> Key: CALCITE-1018
> URL: https://issues.apache.org/jira/browse/CALCITE-1018
> Project: Calcite
> Issue Type: Bug
> Reporter: Maryann Xue
>
> getMaxRowCount(RelSubset) defaults to getMaxRowCount(RelNode) and returns
> null, so if the Join rel has its outer child rel as a RelSubset, the
> SortJoinTransposeRule will fail the checkInputForCollationAndLimit check and
> will not proceed to push down a limit through join.
> Before fix of CALCITE-995 and CALCITE-987, getMaxRowCount(RelSubset) would
> return positive infinity, which would cause similar situation but an opposite
> effect as firing the rule infinitely when the join's outer child is a
> RelSubset.
> Neither of the above situation was reflected in the test cases for
> SortJoinTransposeRule in Calcite, since the RelSubset condition was not
> covered by RelOptRule test which uses HepPlanner running with just one or no
> more than a couple of rules together.
> Basically we need a more accurate way to get max row count for RelSubset,
> otherwise checkInputForCollationAndLimit would either always fail or always
> succeed for a Limit over a Join over a RelSubset. But I assume, to be real
> accurate, we'd have to introduce a similar mechanism to one that computes
> bestCost in RelSubset, which I doubt would be worth it.
> Another way, which might seem a little ugly, is to add something like
> "isSortPushedThrough()" in Sort rel, similar to "isSemiJoinDone()" in Join,
> in order to avoid the rule being fired infinitely.
> In my Phoenix project, I applied a temporary fix, but it proved to work:
> {code}
> public class PhoenixRelMdMaxRowCount {
> public static final RelMetadataProvider SOURCE =
> ReflectiveRelMetadataProvider.reflectiveSource(
> BuiltInMethod.MAX_ROW_COUNT.method, new
> PhoenixRelMdMaxRowCount());
> private PhoenixRelMdMaxRowCount() {
> }
> public Double getMaxRowCount(RelSubset rel) {
> for (RelNode node : rel.getRels()) {
> if (node instanceof Sort) {
> Sort sort = (Sort) node;
> if (sort.fetch != null) {
> return (double) RexLiteral.intValue(sort.fetch);
> }
> }
> }
>
> return Double.POSITIVE_INFINITY;
> }
> }
> {code}
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