[ https://issues.apache.org/jira/browse/CALCITE-1965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16140440#comment-16140440 ]
Christian Beikov commented on CALCITE-1965: ------------------------------------------- Does it make any sense to have an inner join after an outer join for _simple equality joins_? By doing that, you essentially force inner join semantics on the left joins. That's one reason why I only handle plain equality predicates of outer joins. I haven't thought too much about a possible problematic scenario yet, but I will certainly try. If you come up with a counter example before me, please let me know. It would be very nice if you knew a more general approach to this that might even allow rewrites in even more cases, I would really love that. I haven't read the paper nor looked into the matching or rewriting algorithm so I'm not sure if I am the right person to do anything in there. You seem to already have an idea about how to tackle that problem :) Do I understand you correctly, that the changes in {{getAllPredicates}} are ok or at least that the general idea of pulling up the {{OR(ISNULL(),=())}} instead of {{=()}} is correct? I'm asking because I'd like to use that method to determine the predicates of a table that are essential to it's results. When checking these predicates against change sets, one could determine if a data change affected the data which is a nice thing to have for materialized views :) > Support outer joins for materialized views > ------------------------------------------ > > Key: CALCITE-1965 > URL: https://issues.apache.org/jira/browse/CALCITE-1965 > Project: Calcite > Issue Type: Improvement > Components: core > Reporter: Christian Beikov > Assignee: Julian Hyde > > Currently, only inner joins are supported for materialized view > substitutions. The support for outer joins involves creating new pulled up > predicates in case of outer joins that represent semantics of the join. For a > join predicate like "a.id = b.id" the inner join just pulls up that > predicate. When having a left join like e.g. {{select * from a left join b on > a.id = b.id}}, the actual pulled up predicate would be {{OR(=(a.id, > b.id),ISNULL(b.id))}}. For a right join it would be {{OR(=(a.id, > b.id),ISNULL(a.id))}} and for a full outer join it would be {{OR(=(a.id, > b.id),ISNULL(a.id),ISNULL(b.id))}} -- This message was sent by Atlassian JIRA (v6.4.14#64029)