I am used to Microsoft SQL server, but I have a task requiring use of a clients Influx server
From what I understand of the schema, and what I've been able to explore with the CLI, once you select a database, you can view all the field keys in that database, but there are not field keys that are exclusive to each measurement.
Is this true? If not, I will make a second question regarding how to access the field keys that ARE exclusive to a measurement and I will link it immediately following an answer.
Relevant links are
https://docs.influxdata.com/influxdb/v1.7/concepts/crosswalk/
https://docs.influxdata.com/influxdb/v1.8/query_language/explore-schema/
I have tried using client.query("SHOW FIELD KEYS").get_points() and it returns all field keys in all measurements in the database, since the client is only connected at the database level. But there does not seem to be a "use " options, like exists for "use "
Yes, each measurement has its own columns or field keys.
You can get the columns that are relevant to a single measurement by using
columns = client.query("SHOW FIELD KEYS").get_points(measurement = measurement_selection)
where measurement_selection is a string that matches the name of the measurement you wish to observe
Related
I'm new to InfluxDB. I currently have two databases in influx. I now want to copy certain data points from a measurement in the database1, then I want to introduce a couple field sets manually and modify the few field values that I copied and finally insert the changed data points in database2 under a different measurement.
I can use the select into statement however that will not allow me to make changes to the datapoint.
If I use the Insert command I will have to type all the field sets and tag sets individually.
I have a solution that I can use python and query the data points and manipulate the data then insert it back. However that will be a lengthy process.
Is there any easy way to accomplish this task?
Thanks.
I have some data like this which I am putting in influx DB.
measurement userA=10,userB=20,userC=30 1475777099000000000
measurement userZ=11,userA=12,userB=31 1475777199000000000
is it possible to dynamically pick up userA,B,C,Z for a grafana plot? or shall I change my schema?
I'd probably consider changing your schema so that userA, userB, userC, userZ are tags with a single field called value.
For example:
measurement,user=A value=10 1475777099000000000
measurement,user=B value=20 1475777099000000000
measurement,user=C value=30 1475777099000000000
measurement,user=Z value=11 1475777199000000000
measurement,user=A value=12 1475777199000000000
measurement,user=B value=31 1475777199000000000
This way you can GROUP BY user and dynamically pick up on each of the users.
I've recently taken over support of a system which uses Advantage Database Server as its back end. For some background, I have years of database experience but have never used ADS until now, so my question is purely about how to implement a standard pattern in this specific DBMS.
There's a stored procedure which has been previously developed which manages an ID column in this manner:
#ID = (SELECT ISNULL(MAX(ID), 0) FROM ExampleTable);
#ID = #ID + 1;
INSERT INTO Example_Table (ID, OtherStuff)
VALUES (#ID, 'Things');
--Do some other stuff.
UPDATE ExampleTable
SET AnotherColumn = 'FOO'
WHERE ID = #ID;
My problem is that I now need to run this stored procedure multiple times in parallel. As you can imagine, when I do this, the same ID value is getting grabbed multiple times.
What I need is a way to consistently create a unique value which I can be sure will be unique even if I run the stored procedure multiple times at the same moment. In SQL Server I could create an IDENTITY column called ID, and then do the following:
INSERT INTO ExampleTable (OtherStuff)
VALUES ('Things');
SET #ID = SCOPE_IDENTITY();
ADS has autoinc which seems similar, but I can't find anything conclusively telling me how to return the value of the newly created value in a way that I can be 100% sure will be correct under concurrent usage. The ADS Developer's Guide actually warns me against using autoinc, and the online help files offer functions which seem to retrieve the last generated autoinc ID (which isn't what I want - I want the one created by the previous statement, not the last one created across all sessions). The help files also list these functions with a caveat that they might not work correctly in situations involving concurrency.
How can I implement this in ADS? Should I use autoinc, some other built-in method that I'm unaware of, or do I genuinely need to do as the developer's guide suggests, and generate my unique identifiers before trying to insert into the table in the first place? If I should use autoinc, how can I obtain the value that has just been inserted into the table?
You use LastAutoInc(STATEMENT) with autoinc.
From the documentation (under Advantage SQL->Supported SQL Grammar->Supported Scalar Functions->Miscellaneous):
LASTAUTOINC(CONNECTION|STATEMENT)
Returns the last used autoinc value from an insert or append. Specifying CONNECTION will return the last used value for the entire connection. Specifying STATEMENT returns the last used value for only the current SQL statement. If no autoinc value has been updated yet, a NULL value is returned.
Note: Triggers that operate on tables with autoinc fields may affect the last autoinc value.
Note: SQL script triggers run on their own SQL statement. Therefore, calling LASTAUTOINC(STATEMENT) inside a SQL script trigger would return the lastautoinc value used by the trigger's SQL statement, not the original SQL statement which caused the trigger to fire. To obtain the last original SQL statement's lastautoinc value, use LASTAUTOINC(CONNECTION) instead.
Example: SELECT LASTAUTOINC(STATEMENT) FROM System.Iota
Another option is to use GUIDs.
(I wasn't sure but you may have already been alluding to this when you say "or do I genuinely need to do as the developer's guide suggests, and generate my unique identifiers before trying to insert into the table in the first place." - apologies if so, but still this info might be useful for others :) )
The use of GUIDs as a surrogate key allows either the application or the database to create a unique identifier, with a guarantee of no clashes.
Advantage 12 has built-in support for a GUID datatype:
GUID and 64-bit Integer Field Types
Advantage server and clients now support GUID and Long Integer (64-bit) data types in all table formats. The 64-bit integer type can be used to store integer values between -9,223,372,036,854,775,807 and 9,223,372,036,854,775,807 with no loss of precision. The GUID (Global Unique Identifier) field type is a 16-byte data structure. A new scalar function NewID() is available in the expression engine and SQL engine to generate new GUID. See ADT Field Types and Specifications and DBF Field Types and Specifications for more information.
http://scn.sap.com/docs/DOC-68484
For earlier versions, you could store the GUIDs as a char(36). (Think about your performance requirements here of course.) You will then need to do some conversion back and forth in your application layer between GUIDs and strings. If you're using some intermediary data access layer, e.g. NHibernate or Entity Framework, you should be able to at least localise the conversions to one place.
If some part of your logic is in a stored procedure, you should be able to use the newid() or newidstring() function, depending on the type of the backing column:
INSERT INTO Example_Table (newid(), OtherStuff)
I'm using Amazon's SimpleDB Java client to read data from SimpleDB. The problem I have is even though I specified the columns in the some order in the SelectRequest like the following:
SelectRequest req = new SelectRequest("SELECT TIMESTAMP, TYPE, APP, http_status, USER_ID from mydata");
SElectResult res = _sdb.select(req);
..
It returned data in following column order:
APP, TIMSTAMP, TYPE, USER_ID, http_status,
It seems it automatically reordered the columns in ascend order. Is there any way I can force the order as I specified in the select clause?
The columns returned are not an ordered list but an unordered set of attributes. You can't control the order they come back in. SELECT is designed to work even in cases where some of the attributes in your query don't exist for every (or any) returned items. In those cases specifically you wouldn't be able to rely on order anyway. I realize that's small consolation if you have structured your data set so that the attributes are always present.
However, since you know the desired order ahead of time, it should be pretty easy to pull the data out of the result in the proper order. It's just XML after all, or in the case of the Java client, freshly parsed XML.
The Select operation returns a set of Attributes for ItemNames that match the select expression.
SimpleDB docs for SELECT
My team is working on an application with a legacy database that uses two different values as unique identifiers for a Group object: Id is an auto-incrementing Identity column whose value is determined by the database upon insertion. GroupCode is determined by the application after insertion, and is "Group" + theGroup.Id.
What we need is an algorithm to generate GroupCode's that:
Are unique.
Are reasonably easy for a user to type in correctly.
Are difficult for a hacker to guess.
Are either created by the database upon insertion, or are created by the app before the insertion (i.e. not dependent on the identity column).
The existing solution meets the first two criteria, but not the last two. Does anyone know of a good solution to meet all of the above criteria?
One more note: Even though this code is used externally by users, and even though Id would make a better identifier for other tables to link their foreign keys to, the GroupCode is used by other tables to refer to a specific Group.
Thanks in advance.
Would it be possible to add a new column? It could consist of the Identity and a random 32-bit number.
That 64 bit number could then be translated to a «Memorable Random String». It wouldn't be perfect security wise but could be good enough.
Here's an example using Ruby and the Koremutake gem.
require 'koremu'
# http://pastie.org/96316 adds Array.chunk
identity=104711
r=rand(2**32)<<32 # in this example 5946631977955229696
ka = KoremuFixnum.new(r+identity).to_ka.chunk(3)
ka.each {|arr| print KoremuArray.new(arr).to_ks + " "}
Result:
TUSADA REGRUMI LEBADE
Also check out Phonetically Memorable Password Generation Algorithms.
Have you looked into Base32/Base36 content encoding? Base32 representation of a Identity seed column will make it unique, easy to enter but definitely not secure. However most non-programmers will have no idea how the string value is generated.
Also using Base32/36 you can maintain normal database integer based primary keys.