mvzink opened a new pull request, #1997:
URL: https://github.com/apache/datafusion-sqlparser-rs/pull/1997
This PR improves the situation for defining indexes using `CREATE INDEX`,
`ALTER TABLE`, and `CREATE TABLE`, by parsing more MySQL options after the
column list. (It doesn't really affect key definitions written as options on
column definitions.)
The main benefit is supporting MySQL's preferred syntax for `USING { BTREE |
HASH }`, whic is to place it after the column list, instead of before:
```sql
-- before: SQL standard, used for example by Postgres
CREATE TABLE t (x INT, KEY idx_name USING BTREE (x));
-- after: preferred by MySQL
CREATE TABLE t (x INT, KEY idx_name (x) USING BTREE);
```
By "preferred", I mean that MySQL, accepts both forms, but (1) the
documentation states the former is deprecated, and (2) if you run `SHOW CREATE
TABLE` on a table with such an index, it will rewrite the `USING` to come after
the column list.
This is accomplished by parsing index options generically after the column
list, which currently includes `COMMENT` and `USING`. This means these
locations will also benefit from future expansion of index option parsing, such
as `VISIBLE` and `WITH PARSER`. The downside to this approach is that to
continue to support the standard syntax which requires `USING` *before* the
column list, there are now two places where `USING` *could* be stored in the
AST (the distinct `index_type` field or in the `index_options` list). I think
this is acceptable to enable broad support and good fidelity.
A secondary benefit is also supporting a subset of MySQL's `ALTER` options
for `CREATE INDEX`: it accepts `ALGORITHM` and `LOCK` options after the index
options.
A final, tertiary benefit is rationalizing the code organization by moving
`CreateIndex` and `CreateTable` from `dml.rs` to `ddl.rs`.
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