Rewrite joins written with the USING construct

[systay]

If a join has been expressed as:

FROM tblA JOIN tblB USING (col1,col2)

it will be rewritten to

FROM tblA JOIN tblB ON tblA.col1 = tblB.col1 AND tblA.col2 = tblB.col2

This allows our planner to recognize these queries and plan them correctly.

[derekperkins]

Will this collapse the USING columns on the way out? AFAIK, that's the only functional difference between these two joins.

[sougou]

I vaguely remember that there was a specific corner case where this approach wouldn't work. I'll need to dig into some more info to find out why.

[sougou]

Ok. I remember now. It becomes ambiguous in the case of multi-table joins (if we don't know the schema). We'll need to lookup the documentation.

[systay]

Ok. I remember now. It becomes ambiguous in the case of multi-table joins (if we don't know the schema)

The differences are all around which columns are available in the result set.

Here are two examples that show differences that we would need to handle:

> select a from t as t1 join t as t2 on t1.a = t2.a limit 1;
(1052, "Column 'a' in field list is ambiguous")

> select a from t as t1 join t as t2 using (a) limit 1;
+---+
| a |
+---+
| 0 |
+---+
1 row in set
Time: 0.016s

> select * from t as t1 join t as t2 using (a) limit 1;
+---+
| a |
+---+
| 0 |
+---+
1 row in set
Time: 0.013s
> select * from t as t1 join t as t2 on t1.a = t2.a limit 1;
+---+---+
| a | a |
+---+---+
| 0 | 0 |
+---+---+
1 row in set
Time: 0.008s

TL;DR; Changing the JOIN also changes the output, which I did not expect. This rewrite is not as easy as I first thought. Backing off for now. :(

[harshit-gangal]

add a test for non-vindex column in projection to see if that works

[systay]

we're not touching this logic at all. all we are doing is rewriting USING to ON in the rewriter

[GuptaManan100]

Fixes #7119

[systay]

Very limited support for using JOIN ... USING.

Limitations:

• SELECT * is already not supported in for scatter joins, but double not supported for this form of join syntax.
• No more than two tables can be joined this way.

Some frameworks seem to need at least this form (#7119), and so this PR seemed like an acceptable path forward in lieu of more substantial reworking of the join planning.