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Thread: How to append an element to a row inside a 2-dim. array?

How to append an element to a row inside a 2-dim. array?

From
Stefan Keller
Date:
Hi,

Question regarding arrays: How can I append an element to a row inside
a 2-dim. array?
See example below.
And:
Does anybody have experiences how arrays perform if data grows (it's
"read-mostly")?

Yours, Stefan

--
-- Arrays Test
--

CREATE TABLE ourarrtable (id int primary key, arr int[]);

INSERT INTO ourarrtable VALUES (1, '{1,2,3}');
INSERT INTO ourarrtable VALUES (2, '{{11,12,13},{21,22,23},{31,32,33}}');

SELECT * FROM ourarrtable ORDER BY id;
/*
1;"{1,2,3}"
2;"{{11,12,13},{21,22,23},{31,32,33}}"
*/
SELECT arr[1:1] FROM ourarrtable WHERE id=2;
-- "{{11,12,13}}"

-- Works for 1-dim. array in row 1:
UPDATE ourarrtable SET arr = array_append(arr, 4) WHERE id = 1;

-- How to append say number 14 to '{11,12,13}' inside 2-dim. array?
UPDATE ourarrtable SET arr[1:1] = array_cat(arr[1:1], 14) WHERE id = 1;
/*
ERROR:  Function array_cat(integer[], integer) does not exist
LINE 1: UPDATE ourarrtable SET arr[1:1] = array_cat(arr[1:1], 14) WH...
*/

Re: How to append an element to a row inside a 2-dim. array?

From
Stefan Keller
Date:
... and I'm wondering if an index really speeds up array functions:
CREATE INDEX idx_ourarrtable_arr ON ourarrtable USING GIN(arr);

Stefan

2013/3/11 Stefan Keller <sfkeller@gmail.com>:
> Hi,
>
> Question regarding arrays: How can I append an element to a row inside
> a 2-dim. array?
> See example below.
> And:
> Does anybody have experiences how arrays perform if data grows (it's
> "read-mostly")?
>
> Yours, Stefan
>
> --
> -- Arrays Test
> --
>
> CREATE TABLE ourarrtable (id int primary key, arr int[]);
>
> INSERT INTO ourarrtable VALUES (1, '{1,2,3}');
> INSERT INTO ourarrtable VALUES (2, '{{11,12,13},{21,22,23},{31,32,33}}');
>
> SELECT * FROM ourarrtable ORDER BY id;
> /*
> 1;"{1,2,3}"
> 2;"{{11,12,13},{21,22,23},{31,32,33}}"
> */
> SELECT arr[1:1] FROM ourarrtable WHERE id=2;
> -- "{{11,12,13}}"
>
> -- Works for 1-dim. array in row 1:
> UPDATE ourarrtable SET arr = array_append(arr, 4) WHERE id = 1;
>
> -- How to append say number 14 to '{11,12,13}' inside 2-dim. array?
> UPDATE ourarrtable SET arr[1:1] = array_cat(arr[1:1], 14) WHERE id = 1;
> /*
> ERROR:  Function array_cat(integer[], integer) does not exist
> LINE 1: UPDATE ourarrtable SET arr[1:1] = array_cat(arr[1:1], 14) WH...
> */