Refactor parse_joins #87
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- use `if !self.consume_token(&Token::Comma) { break; }` to consume the
comma and exit the loop if no comma found.
- coalesce two `{ false }` blocks in `consume_token` by using a match guard
This block parses one of:
- `[ INNER ] JOIN <table_factor> <join_constraint>`
- `{ LEFT | RIGHT | FULL } [ OUTER ] JOIN <table_factor> <join_constraint>`
..but it was hard to see because of the duplication.
- reduce duplication in the handling of implicit/cross joins and make the flow of data slightly clearer by returning the `join` instead of pushing it and exiting early. (I wanted the block that currently returns `join` to return one of JoinOperator::* tags, so that `parse_table_factor` and the construction of the `Join` struct could happen after we've parsed the JOIN keywords, but that seems impossible.) - move the check for the NATURAL keyword into the block that deals with INNER/OUTER joins that support constraints (and thus can be preceded by "NATURAL") - add a check for NATURAL not followed by a known join type with a test - add more tests for NATURAL joins (we didn't have any), and fix whitespace bug in `to_string()` that was uncovered (we emitted an extra space: `foo NATURAL JOIN bar `)
Pull Request Test Coverage Report for Build 235
💛 - Coveralls |
benesch
approved these changes
Jun 3, 2019
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Heh, I've got a patch somewhere in my stack that addresses that same whitespace bug. Everything LGTM! |
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I'm going to merge this now, actually, because I've got a patch for #83 coming up that's going to need a rebase. |
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While preparing to add support for the non-standard
CROSS/OUTER APPLY(an alternative syntax for LATERAL invented by MS and adopted by Oracle) I've tweaked the internals ofparse_joinsto reduce code duplication, added tests forNATURALand fixed a couple minor issues (extra whitespace in the serializer and NATURAL being silently eaten when not followed by a JOIN).(This does not change the AST, and doesn't deal with #83.)