Support of INNER JOIN syntax

[sergei-pustovykh]

Support of INNER JOIN syntax

This PR introduces the standard syntax for INNER JOIN operation.

Simple case

The requests like
SELECT t1.a, t2.b FROM t1 INNER JOIN t2 ON t1.id = t2.id
are executed the same as
SELECT t1.a, t2.b FROM t1, t2 WHERE t1.id = t2.id

Base case

SELECT select-expr FROM t1 INNER JOIN t2 ON join-expr1 INNER JOIN t3 ON join-expr2 INNER JOIN t4 ON join-expr3 WHERE where-expr
works the same as
SELECT select-expr FROM t1, t2, t3, t4 WHERE where-expr AND join-expr1 AND join-expr2 AND join-expr3

[hatyo]

Nice work, and congrats on your first PR. Few minor comments and we can bring it in.

[hatyo]

This assumes that the user always provides an expression, in other words, they always use the syntax on expression, however if they mistakenly use the USING syntax instead, which is permissible as per the grammar rule:

(INNER | CROSS)? JOIN tableSourceItem
      (
        ON expression
        | USING '(' uidList ')'  // <<< on OR using
      )?                                                            #innerJoin

then we get an NPE here (because ctx.expression() is null). It would be better if we catch this case and throw a proper SQLException with ErrorCode.UNSUPPORTED_QUERY.

[sergei-pustovykh]

Added exception using is not yet supported for inner join and test case.
But it looks like a good time to implement using syntax properly and close the inner join case.

[hatyo]

Does it make sense to handle all the interactions with current plan fragment here? instead of visitableTableSourceBase?

i.e. when calling vistInnerJoin we add both the tableSourceItem and expression to the current plan fragment.

[sergei-pustovykh]

make sense!
Addressed

[hatyo]

LGTM.