In short: I would like to use this input:

+---+---+---+
| x | y | z |
+---+---+---+
| 1 | 1 | a |
| 1 | 2 | b |
| 1 | 3 | c |
| 2 | 1 | d |
| 2 | 2 | e |
| 2 | 3 | f |
| 3 | 1 | g |
| 3 | 2 | h |
| 3 | 2 | i |
| . | . | . |
| n | . | .
+---+---+---+

to generate this output:

+---+---------+---------+---------+---------+
| y | z (x=1) | z (x=2) | z (x=3) | z (x=n) |
+---+---------+---------+---------+---------+
| 1 | a       | d       | g       |    .    |
| 2 | b       | e       | h       |    .    |
| 3 | c       | f       | i       |    .    |
+---+---------+---------+---------+---------+

Table sample:

CREATE TABLE "public"."data" (
    "x" text NOT NULL,
    "y" text NOT NULL,
    "z" text NOT NULL,
);

• The goal is to generate the output, in the most efficient way possible.
• max(x) will increase over time (->n)
• max(y) should remain constant but may increase by ~10%
• dynamic creation of z(x) columns & names

So far I have the following:

select * from crosstab('select y, x, z from data order by 1,2')
as ct (y varchar, x1z varchar, x2z varchar, x3z varchar, 
                  x4z varchar, x5z varchar, x6z varchar)
;

which seems to work well (so far):

+----+-----+-----+-----+-----+-----+-----+
| y  | x1z | x2z | x3z | x4z | x5z | x6z |
+----+-----+-----+-----+-----+-----+-----+
| 10 | fo  | ob  | ar  | fo  | ob  | ar  |
| 20 | ob  | ar  | fo  | ob  | ar  | fo  |
| 30 | ar  | fo  | ob  | ar  | fo  | ob  |
+----+-----+-----+-----+-----+-----+-----+

In the previous SQL snippet, I manually defined the static column names. These should based on x values & hence dynamic.

Thoughts?

Playground:

http://sqlfiddle.com/#!18/75750/105/0