Hey Stamatis,
thanks for your help.
Am 18.02.2020 um 19:34 schrieb Stamatis Zampetakis:
Hi Christian,
Long story short: maybe you can achieve what you want by adding a new type
of RexNode. From what I remember quoting is applied to identifiers (schema,
table, column names) so maybe if OLD/NEW are parameters (e.g.,
RexNamedParam) then possibly it does not make sense to quote them.
Right, and actually it is wrong to quote these variables/parameters i.e.
it's an error as PG complains there is no relation with that name.
At row level triggers OLD and NEW refer to a single tuple/row at each point
in time. In this case, OLD and NEW are row type variables, or better say
parameters, with the same type as the table. In Calcite, there are
index-based parameters (RexDynamicParam) but not named parameters as the
one you seem to need. I think named parameters are useful in various
scenarios so possibly we could expand the RexNode hierarchy.
In this case to build the plan probably it suffices to create and plug the
parameter wherever you need.
That sounds great and just about what I would need. Is there an issue
for this already?
At statement level triggers OLD and NEW refer to set of tuples/rows at each
point in time. In this case, OLD and NEW appear as (temporary)
relations/tables with the same type as the table. In terms of
implementation, I assume that the user defined query acts as a subquery
correlated with OLD/NEW as necessary.
Correct, but right now I am using row level triggers. I'll try to
introduce somekind of synthetic view that holds the state so I can use a
TransientScan for now.
In this case to build the plan probably you need to introduce scan
operations over OLD/NEW tables and create a correlation with the rest of
the query.
As of PG10 the REFERENCING clause can be used to introduce a temporary
view for an old and new relation.
Best,
Stamatis
On Tue, Feb 18, 2020 at 7:03 PM Christian Beikov <[email protected]>
wrote:
My issue is not about parsing. I already have the relational model, I
parsed a query to which I want to add add a condition to a RelNode. Now I
want to add a RexNode to the LogicalFilter node that renders to:
NEW."somecolumn"
How would I construct a RexNode that renders to that when converting the
RelNode to SQL. Do I have to extend the SqlDialect to support that?
Danny Chan <[email protected]> schrieb am Di., 18. Feb. 2020, 15:12:
If you want to make NEW a normal sql identifier, you should override it
in
the parser to make it unreserved.
Christian Beikov <[email protected]>于2020年2月18日 周二下午3:11写道：
Hey Danny,
it's not a view, it's a variable in PL/SQL with a row type. The thing
is, variable names must not be quoted, but I have no idea how to avoid
quoting for this single use case with the relational algebra model in
Calcite.
Regards,
Christian
Am 18.02.2020 um 04:22 schrieb Danny Chan:
From the case you gave, the “variable” seems a view ? Sorry I’m not
familiar with the traditional RDBMS.
Best,
Danny Chan
在 2020年2月17日 +0800 PM1:27，Christian Beikov <
[email protected]
，写道：
Hello,
I asked this before but I guess the question got too big, so I
thought
splitting it up might be better.
I am trying to generate a query from a relational model on which I
did a
few tranformations but I don't know how to refer to a "variable".
In a SQL trigger, there usually are two variable "OLD" and "NEW"
which I
want to be able to refer to. I tried introducing a "transient scan",
but
unfortunately that won't work because this is not a relation and
can't
be quoted. I will workaround this for now by introducing a temporary
relation in the trigger so that I can refer to it, but ideally I
want
to
refer to the variable directly.
The simplest example SQL that I want to be able to produce would
look
like this:
select NEW."some_column"
The tricky part here is that NEW is not quoted. I don't know how I
can
represent this in a relation expression.
Thanks in advance for any help!
Regards,
Christian
