I wish to delete all records in a table on every 10 seconds time interval. I had seen similar queries, but it is not working for me.Here i tried a query
CREATE EVENT DO_DELETE_OP
ON SCHEDULE
EVERY 10 SECOND
DO DELETE FROM tblnew ;
where tblnew is my tablename. Please help me
Your code is working fine .In order for this to work, you will need to enable the mysql scheduler, which can be done like this:
SET GLOBAL event_scheduler = ON;
Related
If I have large amounts of data in a table defined like
CREATE TABLE sensor_values ( ts TIMESTAMPTZ(35, 6) NOT NULL,
value FLOAT8(17, 17) DEFAULT 'NaN' :: REAL NOT NULL,
sensor_id INT4(10) NOT NULL, );
Data comes in every minute for thousands of points. Quite often though I need to extract and work with daily values over years (On a web frontend). To aid this I would like a sensor_values_days table that only has the daily sums for each point and then I can use this for faster queries over longer timespans.
I don't want a trigger for every write to the db as I am afraid that would slow down the already bottle neck of writes to the db.
Is there a way to trigger only after so many rows have been inserted ?
Or perhaps an index and maintains a index of a sum of entries over days ? I don't think that is possible.
What would be the best way to do this. It would not have to be very up to date. Losing the last few hours or a day would not be an issue.
Thanks
What would be the best way to do this.
Install clickhouse and use AggregatingMergeTree table type.
With postgres:
Create per-period aggregate table. You can have several with different granularity, like hours, days, and months.
Have a cron or scheduled task run at the end of each period plus a few minutes. First, select the latest timestamp in the per-period table, so you know at which period to start. Then, aggregate all rows in the main table for periods that came after the last available one. This process will also work if the per-period table is empty, or if it missed the last update then it will catch up.
In order to do only inserts and no updates, you have to run it at the end of each period, to make sure it got all the data. You can also store the first and last timestamp of the rows that were aggregated, so later if you check the table you see it did use all the data from the period.
After aggregation, the "hour" table should be 60x smaller than the "minute" table, that should help!
Then, repeat the same process for the "day" and "month" table.
If you want up-to-date stats, you can UNION ALL the results of the "per day" table (for example) to the results of the live table, but only pull the current day out of the live table, since all the previous days's worth of data have been summarized into the "per day" table. Hopefully, the current day's data will be cached in RAM.
It would not have to be very up to date. Losing the last few hours or a day would not be an issue.
Also if you want to partition your huge table, make sure you do it before its size becomes unmanageable...
Materialized Views and a Cron every 5 minutes can help you:
https://wiki.postgresql.org/wiki/Incremental_View_Maintenance
In PG14, we will have INCREMENTAL MATERIALIZED VIEW, but for the moment is in devel.
I can do this using multiple commands in C# for the app I'm creating, but prefer a stored proc to eliminate issues with latency/locks, etc. (hopefully):
I have a table of 10 extensions (important fields):
SortOrder, Extension, IsUsed
First record will be set to IsUsed = true
When calling the stored proc, I need the IsUsed of the NEXT record in sort order to be set to true,the current record that is true set to false. When I hit the last record, rotate back to the first record.
Use Case: I need to rotate through a bank of usable numbers. Multiple people use the app, so cannot reuse. a number within the last 4 minutes (Bank of 10 will suffice, but we can extend if necessary). When the user requests a number, they get the next avail. I can build the table however needed, so any and all options to achieve use case are welcome.
I need to set the flag to true on the 1st record when stored proc is called. All other records should be false.
I have seen this, which is of interest, but doesn't quite answer:
Get "next" row from SQL Server database and flag it in single transaction
If all that you're using this for is to return a number to identify a session, I'd suggest scrapping the whole table idea and letting SQL Server do the work for you.
You can create a SEQUENCE object that will cycle and return the next value for you, without needing to write any code or maintain any tables.
CREATE SEQUENCE dbo.Extension
AS integer
START WITH 5
INCREMENT BY 5
MINVALUE 5
MAXVALUE 50
CYCLE;
This will return the number 5 the first time it's called, up to the number 50 on call number 10, and then start back over. You can adjust the numbers in the code to more or less do whatever you would like, though.
Get the next value like this:
SELECT NEXT VALUE FOR dbo.Extension;
And when/if you need to extend the range:
ALTER SEQUENCE dbo.Extension
MAXVALUE 100;
Play around with the idea on the Rextester demo.
Edit: In light of the comments above and below, I'd still stick with a SEQUENCE, I think.
Every time your code calls the table for an extension, use a query along the lines of this:
SELECT
Extension
FROM
ExtTable
WHERE
SortOrder = NEXT VALUE FOR dbo.Extension;
Functionally, this should do what you're after, again with no code to write or maintain.
I have a query from another thread which goes through a list of different events and pulls out the most recent event and puts it into a list. The code I'm using is:
SELECT Cleaning1, Max(Date1) AS most_recent
FROM CleaningLog
GROUP BY Cleaning1;
Cleaning1 is the column that has the different cleanings, and Date1 is the column that has the date the cleaning occurred, and CleaningLog is the name of the table. I currently have a macro in Access which is an OpenQuery, query. I am having it open the above query, and then having it view as a data sheet and it's in edit mode.
What I am stuck on, is getting a subsequent macro/query/vba code to take the datasheet the query produces and going through each item and determining if they're over due to be cleaned. I tried having a Make Table query, but the problem is, there is no user friendly way to refresh that table without having to delete it (I am having unskilled workers use this Access sheet).
I am wondering if there's a way to look at the most recent cleaning's date, what the query produces, and filter the dates out that are over due for a cleaning, specified by a parameter. I have been looking at this webpage to start playing with the notation, but I haven't been able to come up with much that is useful.
https://support.office.com/en-us/article/Examples-of-query-criteria-3197228C-8684-4552-AC03-ABA746FB29D8
Another problem that I am encountering is that each cleaning doesn't have the same time frame in which is needs to be cleaned.
Thank you in advance for any help!!
You should just be able to modify the query above to show entries with a max date lower than they should be. Below shows entries that haven't been cleaned in 30 days, for instance.
SELECT Cleaning1, Max(Date1) AS most_recent
FROM CleaningLog
GROUP BY Cleaning1
HAVING Max(Date1) < Now() - 30;
I am building reports with Eclipse BIRT and got to a problem with the scales of the x-axis. I am getting my input with a select-string out of a database table. There I have events from a Nagios-log-file, with timestamps for every events begin and end. Out of them I create a time like hh:mm, this is enough, it doesn't have to have the seconds or the date (These I select somewhere else). For every event I get a 1 or a 0, representing up- and downtimes.
Now I want to built the report so that I have the scaling of the x-axis for all 1440 Minutes of the day, just changing the state (to 0) when there is a downtime. I've already tried to format the scale, but it doesn't work at all. After days of searching and 'try and error' I am now asking for help. Is there a way to format the chart the way I need and how could it be done?
The last idea of mine was to have another table with every minute inculded from which I select the data and to update this table with the event-data from the nagios-log-table, but this doens't seem to be an adequate solution. Maybe there is something simple I am just not able to see right now.
P.S.: I am fairly new in this and the eclipse manual did not help me with this specific problem. I also know that there are easy, simply and amazing ways to get those kinds of report out of nagios, but I have to do it with BIRT...
I finally found a way to get the report the way I needed.
I am joining my data_table with "generate_series" to get the missing data for every minute.
The postgresql statement looks like:
select *, coalesce(updown, 1)
from generate_series ('19.12.2015 00:00'::timestamp, '19.12.2015 23:59', '1 minute')
left join data_table
on date_trunc('minute',to_timestamp(date_ts)) = generate_series
and host like '%host%';
This may not be the best way to do it, but it worked for me and maybe it is also helpful for others. To usw this with BIRT I just replaced the host and the dates with the parameter-sgn "?".
Tough problem I am working on here.
I have a table of CustomerIDs and CallDates. I want to measure whether there is a 'repeat call' within a certain period of time (up to 30 days).
I plan on creating a parameter called RepeatTime which is a range from 0 - 30 days, so the user can slide a scale to see the number/percentage of total repeats.
In Excel, I have this working. I sort CustomerID in order and then sort CallDate from earliest to latest. I then have formulas like:
=IF(AND(CurrentCustomerID = FutureCustomerID, FutureCallDate - CurrentCallDate <= RepeatTime), 1,0)
CurrentCustomerID = the current row, and the FutureCustomerID = the following row (so it is saying if the customer ID is the same).
FutureCallDate = the following row and the CurrentCallDate = the current row. It is subtracting the future call time from the first call time to measure the time in between.
The goal is to be able to see, dynamically, how many customers called in for a specific reason within maybe 4 hours or 1 day or 5 days, etc. All of the way up until 30 days (this is our actual metric but it is good to see the calls which are repeats within a shorter time frame so we can investigate).
I had a similar problem, see here for detailed version Array calculation in Tableau, maxif routine
In your case, that is basically the same thing as mine, so you could apply that solution, but I find it easier to understand the one I'm about to give, I would do:
1) Create a calculated field called RepeatTime:
DATEDIFF('day',MAX(CallDates),LOOKUP(MAX(CallDates),-1))
This will calculated how many days have passed since the last call to the current. You can add a IFNULL not to get Null values for the first entry.
2) Drag CustomersID, CallDates and RepeatTime to the worksheet (can be on the marks tab, don't need to be on rows or column).
3) Configure the table calculation of RepeatTIme, Compute using Advanced..., partitioning CustomersID, Adressing CallDates
Also Sort by Field CallDates, Maximum, Ascending.
This will guarantee the table calculation works properly
4) Now you have a base that you can use for what you need. You can either export it to csv or mdb and connect to it.
The best approach, actually, is to have this RepeatTime field calculated outside Tableau, on your database, so it's already there when you connect to it. But this is a way to use Tableau to do the calculation for you.
Unfortunately there's no direct way to do this directly with your database.