moveJoinConditionsToFilter bug #1202
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| case *plan.Filter: | ||
| return false | ||
| return transform.NodeWithCtx(node, func(transform.Context) bool { return true }, func(c transform.Context) (sql.Node, transform.TreeIdentity, error) { | ||
| if c.Node != topJoin { |
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Does this function run recursively up the tree, so each join node gets a turn to be the top node?
I'm curious how this interacts with pushdown, could use some more plan tests.
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There will always be one topJoin in a single scope. You would need a subquery, union, etc to get a second scope. If we know the joins are all compact in the tree, we could probably have this whole rule just be a single transform. When we hit a node that isn't a join and the topJoin is not nil we combine the conditions turned where filters. The relationship to pushdown is what you were telling me yesterday: this rule only moves filters from join to where clause, pushdown decides how low filters can be pushed.
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The move join condition rule selects filters not needed as a join condition, identify the target parent for the filter, and then moves the plucked filters to EVERY child of the parent of the join node. The correct behavior is to move the filter immediately above the join whose condition we plucked the filter from.