Fix for More Than Two Disjunction Predicate

[wuwenw]

Add support for #1058. In the Conjunction Translator constructor, prepare() would recursively create translator for children, so we just need to loop through them.

Sample SQL test:

terrier=# CREATE TABLE xxx1 (id INT, data INT, time INT);
CREATE TABLE
terrier=# INSERT INTO xxx1 VALUES (1, 10, 100),(2, 20, 200),(3, 30, 300),(4, 40, 400);
INSERT 0 4
terrier=# SELECT * FROM xxx1 WHERE id=1 OR id=2 OR id=3 OR id=4;
 id | data | time
----+------+------
  1 |   10 |  100
  2 |   20 |  200
  3 |   30 |  300
  4 |   40 |  400
(4 rows)

terrier=# SELECT * FROM xxx1 WHERE id=1 AND data=10 AND time=100 OR id=2;
 id | data | time
----+------+------
  1 |   10 |  100
  2 |   20 |  200
(2 rows)

terrier=# SELECT * FROM xxx1 WHERE (id=1 OR data=10 AND time=200) AND (time=100 OR id=2);
 id | data | time
----+------+------
  1 |   10 |  100
(1 row)

terrier=# SELECT * FROM xxx1 WHERE (id=2 OR (id=1 AND (time=100 AND data=10))) OR (id=3 AND data=30);
 id | data | time
----+------+------
  1 |   10 |  100
  2 |   20 |  200
  3 |   30 |  300
(3 rows)

terrier=# SELECT * FROM xxx1 WHERE id=1 OR time=300 AND id=3 OR id=4 AND time=200 OR id=2 AND data=20 OR id=5;
 id | data | time
----+------+------
  1 |   10 |  100
  2 |   20 |  200
  3 |   30 |  300
(3 rows)

[codecov]

Codecov Report

Merging #1064 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1064   +/-   ##
=======================================
  Coverage   80.77%   80.77%           
=======================================
  Files         668      668           
  Lines       42731    42731           
=======================================
  Hits        34516    34516           
  Misses       8215     8215           

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[apavlo]

Please add test SQL from @dniu16

[apavlo]

LGTM