22.03.2021 11:14, Mark Rotteveel wrote:
It turns out that RETURNING is not a reserved word, which allows
statements like:
```
SQL> create table returning (returning boolean);
SQL> insert into returning (returning) values (true) returning returning
returning;
RETURNING
=========
<true>
SQL> update returning set returning = not returning where returning
returning returning returning;
RETURNING
=========
<false>
```
I had hoped to make a very simple parser to detect the presence of a
RETURNING clause, but the possibility of having columns and expressions
containing RETURNING makes that a lot harder :(. Alternatively, I will
just need to ignore this, and for example detect a `UPDATE ... WHERE
RETURNING` as having a RETURNING clause.
For context, this would be used in Jaybird to replace a slightly more
complicated parser with a third-party dependency I want to get rid of.
Why is RETURNING not a reserved word?
Because it's non-standard. We usually don't introduce new reserved words
unless they're standard or cause conflicts in the parser (*).
(*) the second rule was not strictly followed in the past, as btyacc
resolves many conflicts automagically
Dmitry
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