Influx: doing math the same fields in different groups - influxdb

I have InfluxDB measurement currently set up with following "schema":
+----+-------------+-----------+
| ts | cost(field) | type(tag) |
+----+-------------+-----------+
| 1 | 10 | 'a' |
| 1 | 20 | 'b' |
| 2 | 12 | 'a' |
| 2 | 18 | 'b' |
| 2 | 22 | 'c' |
+------------------+-----------+
I am trying to write a query that will group my table by timestamp and get a delta between field values of two different tags. If I want to get delta between tag 'a' and tag 'b', it will give me following result (please not that I ignore tag 'c'):
+----+-----------+------------+
| ts | type(tag) | delta_cost |
+----+-----------+------------+
| 1 | 'a' | 10 |
| 2 | 'b' | 6 |
+----+-----------+------------+
Is it something Influx can do or am I using the wrong tool?

Just managed to answer my own question. While one of the obvious ways would be performing self-join, Influx does not support joins anymore. We can, however, use nested selects in a following format:
SELECT MEAN(cost_a) - MEAN(cost_b) as delta_cost
FROM
(SELECT cost as cost_a, tag, tablename where tag='a'),
(SELECT cost as cost_b, tag, tablename where tag='b')
GROUP BY time(60s)
Since I am getting my data every 60 seconds anyway, and I have a guarantee of just one point per tag per 60 seconds, I can use GROUP BY and take MEAN without any problems

Related

How to forecast (or any other function) in Google Sheets with only one cell of data?

My sheet:
+---------+-----------+---------+---------+-----------+
| product | value 1 | value 2 | value 3 | value 4 |
+---------+-----------+---------+---------+-----------+
| name 1 | 700,000 | 500 | 10,000 | 2,000,000 |
+---------+-----------+---------+---------+-----------+
| name 2 | 200,000 | 800 | 20,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 3 | 100,000 | 150 | 6,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 4 | 1,000,000 | 1,000 | 25,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 5 | 2,000,000 | 1,500 | 30,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 6 | 2,500,000 | 3,000 | 65,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 7 | 300,000 | 300 | 12,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 8 | 350,000 | 200 | 9,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 9 | 900,000 | 1,200 | 28,000 | ? |
+---------+-----------+---------+---------+-----------+
| name 10 | 150,000 | 100 | 5,000 | ? |
+---------+-----------+---------+---------+-----------+
What I am attempting is to predict the empty columns based on the data that I do have. Maybe just one of the columns that contain data in every row or maybe I should be only focusing on one column that contains data in every row?
I have used FORECAST previously but had more data in the column that I was predicting values for which the lack of data I think is my root problem(?). Not sure if FORECAST is best for this so any recommendations for other functions are most welcome.
The last thing I can add though is that the known value in column E (value 4) is a confident number and ideally it's used in any formula that I end up with (although I am open to any other recommendations).
The formula I was using:
=FORECAST(D3,E2,$D$2:$D$11)
I don't think this is possible without more information. If you think about it, Value 4 can be a constant (always 2,000,000), be dependent on only one other value (say 200 times value 3), or be a complex formula (say add values 1, 2, and 3 with a constant). Each of these 3 models agree with the values for name 1, however they generate vastly different value 4 predictions.
In the case of name 2, the models would output the following for value 4:
Constant: 2,000,000
Value 3: 8,000,000
Sum: 2,489,700
Each of those values could be valid without providing further constraints (either through data points or specifying the kind of model, but probably both).

Rails: create unique auto-incremental id based on sibling records

I have three models in my rails project, namely User, Game, Match
user can create many matches on each game
so table structure for matches is like
table name: game_matches
+----+---------+---------+-------------+------------+
| id | user_id | game_id | match_type | match_name |
+----+---------+---------+-------------+------------+
| 1 | 1 | 1 | practice | |
| 2 | 3 | 2 | challenge | |
| 3 | 1 | 1 | practice | |
| 4 | 3 | 2 | challenge | |
| 5 | 1 | 1 | challenge | |
| 6 | 3 | 2 | practice | |
+----+---------+---------+-------------+------------+
i want to generate match_name based on user_id, game_id and match_type values
for example match_name should be create like below
+----+---------+---------+-------------+-------------+
| id | user_id | game_id | match_type | match_name |
+----+---------+---------+-------------+-------------+
| 1 | 1 | 1 | practice | Practice 1 |
| 2 | 3 | 2 | challenge | Challenge 1 |
| 3 | 1 | 1 | practice | Practice 2 |
| 4 | 3 | 2 | challenge | Challenge 2 |
| 5 | 1 | 1 | challenge | Challenge 1 |
| 6 | 3 | 2 | practice | Practice 1 |
+----+---------+---------+-------------+-------------+
How can i achieve this auto incremental value in my rails model during new record creation.
Any help suggestions appreciated.
Thanks in advance.
I see two ways you can solve this:
DB: trigger
Rails: callback
Trigger (assuming Postgres):
DROP TRIGGER IF EXISTS trigger_add_match_name ON customers;
DROP FUNCTION IF EXISTS function_add_match_name();
CREATE FUNCTION function_add_match_name()
RETURNS trigger AS $$
BEGIN
NEW.match_name := (
SELECT
CONCAT(game_matches.match_type, ' ', COALESCE(count(*), 0))
FROM game_matches
WHERE game_matches.user_id = NEW.user_id AND game_matches.match_type = NEW.match_type
);
RETURN NEW;
END
$$ LANGUAGE 'plpgsql';
CREATE TRIGGER trigger_add_match_name
BEFORE INSERT ON game_matches
FOR EACH ROW
EXECUTE PROCEDURE function_add_match_name();
Please note that this is not tested.
Rails
class GameMatch
before_create :assign_match_name
private
def assign_match_name
number = GameMatch.where(user_id: user_id, match_type: match_type).count || 0
name = "#{match_type} #{number + 1}"
self.match_name = name
end
end
Again, untested.
I'd prefer the trigger solution since callbacks can be skipped or ommited altogether when inserting via pure SQL.
Also I'd add "match_number" column instead of the full name and then construct the name within the Model or a Decorator or a view Helper (more flexible, I18n) but the logic behind stays the same.
You should retrieve the last match_name for these user and game, split it, increase the counter and join back with a space. Unfortunately, SQL does not provide SPLIT function, so somewhat like below would be a good start:
SELECT match_name
FROM match_name
WHERE user_id = 3
AND game_id = 2
ORDER BY id DESC
LIMIT 1
I would actually better create a match_number column of type INT to keep the number by type and produce a name by concatenation the type with this number.

DGET with array constant as criteria parameter with a blank element

If I have the following table:
\ || A | B | C | D | E | F |
_______________________________________
1 || H1 | H2 | H3 | H4 | 10 | 20 |
2 || 10 | AA | .2 | 70 | 70 | 100 |
3 || 10 | BB | .3 | 80 | | |
4 || 20 | CC | .4 | 90 | | 10 |
5 || 20 | DD | .5 | 100 | | CC |
6 || | | | | | |
(*All workings examples are in Google Docs)
This works:
=DGET(A1:D5,"H3",{A1:D1;E1,E3,E4,E2})
RESULT = 0.2
But I'm looking for a way to have a blank element in the constant array I'm using as the criteria without referencing a blank cell. I need the blank elements as otherwise DGET treats them as criteria to be evaluated.
Something like this:
=DGET(A1:D5,"H4",{A1:D1;E1,#BLANK,#BLANK,E2})
Where #BLANK is whatever magic makes google docs treat the element as empty.
I know that I can do:
=DGET(A1:D5,"H3",{A1,D1;E1,E2})
And just limit the number of columns in the criteria, but I'd like to specify the entire header set in the constant and just choose the columns I want specified.
For instance if I wanted something like this:
=DGET(A1:D5,"H3",{A1:D1;F1,F3,F3,F2;F4,F5,F3,F3})
RESULT = 0.5
But as this:
=DGET(A1:D5,"H3",{A1:D1;F1,#BLANK,#BLANK,F2;F4,F5,#BLANK,#BLANK})
In addition to the primary question of how to set an empty element, I'm curious if there is a way to perform a similar lookup in Excel. LOOKUP functions do not appear to support filtering on multiple criteria and the Database functions don't support arrays for defining criteria (only a cell range).
I believe that the #BLANK you're looking for is:
""
And, No. Excel does not support such sophisticated arrays.

find rows where there is another row with an opposite value in the table

Im trying to find an efficient way to solve the problem:
I need to find all rows in a table where there is another row with an opposite column value.
For example I have transactions with columns id and amount
| id | amount |
|----|--------|
| 1 | 1 |
| 2 | -1 |
| 3 | 2 |
| 4 | -2 |
| 5 | 3 |
| 6 | 4 |
| 7 | 5 |
| 8 | 6 |
The query should return only the first 4 rows:
| id | amount |
|----|--------|
| 1 | 1 |
| 2 | -1 |
| 3 | 2 |
| 4 | -2 |
My current solution is terribly efficient as I am going through 1000's of transactions:
transactions.find_each do |transaction|
unless transactions.where("amount = #{transaction.amount * -1}").count > 0
transactions = transactions.where.not(amount: transaction.amount).order("# amount DESC")
end
end
transactions
Are there any built in Rails or Postgresql functions that could help with this?
Use following query:
SELECT DISTINCT t1.*
FROM transactions t1
INNER JOIN transactions t2 ON t1.amount = t2.amount * -1;
SELECT * FROM the_table t
WHERE EXISTS (
SELECT * FROM the_table x
WHERE x.amount = -1*t.amount
-- AND x.amount > t.amount
);
Consider storing an absolute value indexed column then query for the positive value. Postgres has an absolute value function; but I think the beauty of ActiveRecord is that Arel abstracts away the SQL. DB specific SQL can be a pain if you change later.
There is type called abs which will return irrespective of symobol. From my example data is the table name
SELECT id,amount FROM DATA WHERE id = ABS(amount)
This is the sample test table
Here is the output

Can I have a cucumber example with several values in a single column x row position

Hi here is what I what I have:
Scenario Outline: Seatching for stuff
Given that the following simple things exists:
| id | title | description | temp |
| 1 | First title | First description | low |
| 2 | Second title | Second description with öl | Medium |
| 3 | Third title | Third description | High |
| 11 | A title with number 2 | can searching numbers find this 2 | Exreme |
When I search for <criteria>
Then I should get <result>
And I should not get <excluded>
Examples
|criteria|results | excluded |
| 1 | 1 | 2,3,11 |
| 11 | 11 | 1,2,3 |
| title | 1,2,3 | 11 |
| öl | 2 | 1,3,11 |
| Fir* | 1 | 2,3,11 |
| third | 3 | 1,2,11 |
| High | 3 | 1,2,11 |
As you can see I'm trying to test a search field for a web-application using cucumber and the scenario outline structure in order to test several search criteria.
I'm not sure how to handle the input I would get as result and excluded in my steps.
Maybe this doesn't work at all?
Is there a workaround?
There's nothing wrong with what you're doing. Cucumber will just take that as a single string. The fact that it's actually comma-separated values means nothing to Cucumber.
Your step definition would still look like this:
Then /^I should not get ([^"]*)$/ do |excluded|
# excluded will be a string, "2,3,11"
values = excluded.split(",")
# Do whatever you want with the values
end

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