subquery support

[thoshiai]

Some patterns using subquery is not supported

[yugo-n]

EXISTS clause and simple subqueries in FROM clause are now supported.

Remaining restrictions are:

• WHERE IN .. (subquery) is not supported

  CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm03 AS SELECT i,j FROM
  mv_base_a WHERE i IN (SELECT i FROM mv_base_b WHERE k < 103 );

• subqueries in target list is not supported

  CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm05 AS SELECT i,j, (SELECT k
  FROM mv_base_b b WHERE a.i = b.i) FROM mv_base_a a;

• nested EXISTS subqueries is not supported

  CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm11 AS SELECT a.i,a.j FROM
  mv_base_a a WHERE EXISTS(SELECT 1 FROM mv_base_b b WHERE EXISTS(SELECT
  1 FROM mv_base_b c WHERE b.i = c.i));

• EXISTS subquery with aggregate function is not supported

  CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm_exists AS SELECT COUNT(*)
  FROM mv_base_a a WHERE EXISTS(SELECT 1 FROM mv_base_b b WHERE a.i =
  b.i) OR a.i > 5;

• EXISTS subquery with condition except AND is not supported.

  CREATE INCREMENTAL MATERIALIZED VIEW mv_ivm10 AS SELECT a.i,a.j FROM
  mv_base_a a WHERE EXISTS(SELECT 1 FROM mv_base_b b WHERE a.i = b.i) OR
  a.i > 5;