Tree of SELECTs -> multi-statement combination of SELECT and CREATE TABLE tN AS SELECT

[carlopi]

Idea (that might be wrong, unsure) is that a single statement is a tree of SELECTs, can be transformed in an equivalent (but rendered bottom-up) tree of CREATE TABLE t{1....N} AS SELECT.

Example:

SELECT CASE  WHEN (((ref_0.p_brand ~~~ ref_0.p_container) OR EXISTS(SELECT ref_1.o_custkey AS c0, ref_0.p_comment AS c1 FROM main.orders AS ref_1 INNER JOIN main.part AS ref_2 ON (EXISTS(SELECT subq_0.c1 AS c0, subq_0.c0 AS c1, ref_3.p_size AS c2, ref_0.p_mfgr AS c3, (SELECT s_suppkey FROM main.supplier LIMIT 1 OFFSET 1) AS c4 FROM main.part AS ref_3 , (SELECT ref_1.o_custkey AS c0, ref_1.o_comment AS c1 FROM main.customer AS ref_4 WHERE (ref_4.c_name IS NULL)) AS subq_0 WHERE (ref_0.p_container ~~ ref_1.o_orderstatus) LIMIT 104)) WHERE EXISTS(SELECT ref_2.p_mfgr AS c0, (SELECT s_name FROM main.supplier LIMIT 1 OFFSET 3) AS c1, ref_1.o_clerk AS c2, ref_0.p_partkey AS c3, (SELECT r_regionkey FROM main.region LIMIT 1 OFFSET 6) AS c4, ref_1.o_orderstatus AS c5, ref_5.r_comment AS c6, ref_5.r_comment AS c7, ref_5.r_regionkey AS c8, ref_2.p_size AS c9, ref_1.o_orderkey AS c10, ref_2.p_mfgr AS c11, 78 AS c12, ref_1.o_custkey AS c13, (SELECT n_regionkey FROM main.nation LIMIT 1 OFFSET 1) AS c14, ref_2.p_container AS c15, ref_5.r_comment AS c16, ref_0.p_comment AS c17, ref_5.r_regionkey AS c18, ref_1.o_orderdate AS c19, ref_0.p_brand AS c20 FROM main.region AS ref_5 WHERE 1 LIMIT 74) LIMIT 121))) THEN (ref_0.p_type) ELSE ref_0.p_type END AS c3, CASE  WHEN ((ref_0.p_size IS NULL)) THEN (ref_0.p_name) ELSE ref_0.p_name END AS c4 FROM main.part AS ref_0 LIMIT 110

(from issue #460 I think)
can likely rendered as

CREATE TABLE t0 AS SELECT n_regionkey FROM main.nation LIMIT 1 OFFSET 1;
CREATE TABLE t1 AS SELECT r_regionkey FROM main.region LIMIT 1 OFFSET 6) AS c4, ref_1.o_orderstatus AS c5, ref_5.r_comment AS c6, ref_5.r_comment AS c7, ref_5.r_regionkey AS c8, ref_2.p_size AS c9, ref_1.o_orderkey AS c10, ref_2.p_mfgr AS c11, 78 AS c12, ref_1.o_custkey AS c13, (SELECT t0) AS c14, ref_2.p_container AS c15, ref_5.r_comment AS c16, ref_0.p_comment AS c17, ref_5.r_regionkey AS c18, ref_1.o_orderdate AS c19, ref_0.p_brand AS c20 FROM main.region AS ref_5 WHERE 1 LIMIT 74;
SELECT CASE  WHEN .... (SELECT t1) .........;

or even adding storage and checkpoints in the middle.