v3: how to draw an owl #1492
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v3: how to draw an owl #1492
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We now need a place to push where clauses and other constructs. We'll need all constructs of a Select statement since that's what we're eventually building.
This will be used for the v3 planbuilder.
Skeletal code to identify the rightmost route where we can push individual parts of a where clause. We also add flags for RouteBuilder and TableAlias if they're on the RHS of a left join.
WHERE clause filters can now be pushed down, and we also perform routing changes if applicable.
There are no colvindexes in the new v3 routes. So, we need a better way to test that the correct vindexes were chosen.
Still need to write more tests. Subqueries won't be addressed till the end.
We need to know the Order of left and right nodes for the join builders. This allow us to know the correct path from the root node to the necessary RouteBuilder.
This part just reuses the filter functions with some slightly modified rules.
Changed the symbol table to have slices because map is overkill for a handful of symbols. Changed select to use rightmost route, just like where clause.
When symbols get resolved, those decisions need to be persisted. Otherwise, the symbol table evolves and introduces new symbols that may hide old ones (when SELECT is parsed). A re-resolution after the fact can produce inconsistent/incorrect results. In other words, we need the original resolution to be remembered when we decide to wire things up at the end.
The symtab Find will now return an error if a reference could not be resolved. It's also now broken out into another function, Vindex, which returns a Vindex of one can be found for the expression.
Merging FindInScope and Find, because it wasn't clear when to use what. Now, Find returns an isLocal flag. This forces you to think if that needs to be checked in the current context.
The previous scheme was hard to implement at execution time. In the new scheme, every join node knows contains info about which vars it needs to supply.
A few features are still to be done, like subquery in FROM clause, but everything is functional end-to-end, and the old v3 tests are passing against the new code. Comprehensive tests need to be written, and the code needs commenting and cleanup.
Allowing '*' expressions for simple routes. This is for supporting legacy apps that may still be using this construct.
Renamed some functions for better readability
Adding NEXTVAL as keyword. This lets us control where this can or cannot be allowed at the parser level. Also, the argument to NEXTVAL is a table name, which is technically a different syntax than a normal function.
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Reviewed 1 of 47 files at r1, 4 of 30 files at r2, 1 of 37 files at r3, 2 of 18 files at r9, 1 of 11 files at r10. go/vt/vtgate/planbuilder/doc.go, line 45 [r13] (raw file): test/vtgatev3_test.py, line 286 [r13] (raw file): test/vtgatev3_test.py, line 753 [r13] (raw file): Comments from the review on Reviewable.io |
Sequences for vttablet: initial cut
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Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com> Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
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@erzel
Ref: http://lmgtfy.com/?q=how+to+draw+an+owl
Well, it's not quite the entire owl, but it's close. As parts get ready, I'll point you to them to perform the review.
In this installment, you may start with doc.go. It's just a description of the high level approaches and issues. There should be no surprises there. You can glance at the rest of the stuff for reference, but comments may be outdated or missing.
I'll probably work on polishing symtab next.