Some time ago I got several docker machines to use. I thought that it’d be nice to identify to which docker machine I’m connected at the moment. As far as I use Powerline status bar, a segment for it is the way to go. I didn’t find anything ready to use, so I had to create my own.

Well, it’s been some time without any posts here. I’m not quite sure why exactly, but I wasn’t encouraged enough, probably. After a while a thought that I have something to write down, but after I saw the old design I decided to fix it first.

Recently, I got a necessity of calculation an average value for each group of a data in my clipboard. To avoid creating a temporary file or using Excel for that, I used awk tool. Just writing it down for a future reference.

Example source data:

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23100 1600
20500 1600
19400 1600
36900 512
43100 512
48000 512

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$ # SUM
$ awk '{arr[$2]+=$1} END {for (i in arr) {print i, arr[i]}}'
512 128000
1600 63000
$ # AVG
$ awk '{arr_sum[$2]+=$1; arr_cnt[$2]+=1} END \
       {for (i in arr_sum) {print i, arr_sum[i]/arr_cnt[i]}}'
512 42666.7
1600 21000

Test:

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CREATE TABLE test_int (
    u32 INT(10) UNSIGNED,
    i32 INT(10)
);

INSERT INTO test_int (u32, i32) VALUES(4294967295, 4294967295);

SELECT * FROM test_int;

Output:

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+------------+------------+
| u32        | i32        |
+------------+------------+
| 4294967295 | 2147483647 |
+------------+------------+

As you can see, MySQL silently cut the value if doesn’t fit to a column type.

For example, PostgreSQL gives the following error in such case:

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ERROR:  smallint out of range

Test for PostgreSQL:

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CREATE TABLE test_int (
    small smallint,
    medium integer
);

INSERT INTO test_int (small, medium) VALUES(4294967295, 4294967295);

😒

I’ve just moved this blog to SSL. It was so easy and completely free, thanks to CloudFlare!