Feature: Syntax support for direct COPY of tables to output format

[ray6080]

API

Other

Description

We don't support directly specify copying a table to output formats. Instead, it has to go through COPYing a subquery.
An example is like this

CREATE NODE TABLE nodeTbl(id INT64 PRIMARY KEY, name STRING);
COPY (MATCH (t:nodeTbl) RETURN t.*) TO 'nodes.parquet';
CREATE REL TABLE relTbl(FROM nodeTbl TO nodeTbl, since DATE);
COPY (MATCH (:nodeTbl)-[e:relTbl]->(:nodeTbl) RETURN e.*) TO 'rels.parquet';

Simpler syntaxes are expected as following:

CREATE NODE TABLE nodeTbl(id INT64 PRIMARY KEY, name STRING);
COPY nodeTbl TO 'nodes.parquet';
CREATE REL TABLE relTbl(FROM nodeTbl TO nodeTbl, since DATE);
COPY relTbl TO 'rels.parquet';