We have a Windows application that we are using to test against a CLICK PLC and a Schneider PLC.
My question is around reading and writing data to the Assembly Object, and more specifically if there is a way to read/write from/to a particular spot in the byte array defined by the Assembly Object instance?
Reading the entire array is not so much of an issue, but we really don't want to write the entire array if all we need to do is write a single value. If we have to write all the values back, don't we risk overwriting some values that could have changed underneath us? Yes, we could do a read, change the single value, then write, but there's is no guarantee that the other values won't have changed between the read and the write.
The PLCs do not support Get/Set_Member, so we cannot use that, which means we are left with Get/Set_Attribute_Single. From looking at the ODVA documentation, Vol 1, Appendix C, section C-1.4.2 it seems to me that I can create an EPATH that should let me do just that by using the Extended Logical Format?
Ex: If I want to read the first element in the byte array, I should be able to construct my padded EPATH using the Extended Logical Format as follows:
EPATH = 20 04 | 24 65 | 30 03 | 3D 01 | 00 00
(Class ID 4, Instance ID 101, Attribute 3, Extended Logical with 16 bit Logical value and Array Index Type, Array Index 0)
If I call Get_Attribute_Single with this EPATH I get a "Path Segment Error" for either PLC.
Is my thinking correct, that I should be able to get an array element?
If so, is my EPATH correct?
If so, could the error be due to either PLC not supporting this?
Related
I have an array that looks like this [[(Double,Double)]]. It's a multi-dimensional array of tuples.
This is data that I will never query on, as it doesn't need to be queried. It only makes sense if it's like that on the client side. I'm thinking of storing the entire thing as string and then parsing it back to multi array.
Would that be a good approach and would the parsing be very expensive considering I can have a max of 20 arrays with 4 max inner array each with a tuple of 2 Double?
How would I check to see which is a better approach and if storing it as multi-dimensional array in PostgreSQL is the better approach?
How would I store it?
To store an array of composite type (with any nesting level), you need a registered base type to work with. You could have a table defining the row type, or just create the type explicitly:
CREATE TYPE dd AS (a float8, b float8);
Here are some ways to construct that 2-dimensional array of yours:
SELECT ARRAY [['(1.23,23.4)'::dd]]
, (ARRAY [['(1.23,23.4)']])::dd[]
, '{{"(1.23,23.4)"}}'::dd[]
, ARRAY[ARRAY[dd '(1.23,23.4)']]
, ARRAY(SELECT ARRAY (SELECT dd '(1.23,23.4)'));
Related:
How to pass custom type array to Postgres function
Pass array from node-postgres to plpgsql function
Note that the Postgres array type dd[] can store values with any level of nesting. See:
Mapping PostgreSQL text[][] type and Java type
Whether that's more efficient than just storing the string literal as text very much depends on details of your use case.
Arrays types occupy an overhead of 24 bytes plus the usual storage size of element values.
float8 (= double precision) occupies 8 bytes. The text string '1' occupies 2 bytes on disk and 4 bytes in RAM. text '123.45678' occupies 10 bytes on disk and 12 bytes in RAM.
Simple text will be read and written a bit faster than an array type of equal size.
Large text values are compressed (automatically), which can benefit storage size (especially with repetitive patterns) - but adds compression / decompression cost.
An actual Postgres array is cleaner in any case, as Postgres does not allow illegal strings to be stored.
I wish to have stored many (N ~ about 150) boolean values of web app "environment" variables.
What is the proper way to get them stored?
creating N columns and one (1) row of data,
creating two (2) or three (3) columns (id smallserial, name varchar(255), value boolean) with N rows of data,
by using jsonb data type,
by using area data type,
by using bit string bit varying(n),
by another way (please advise)
Note: name may be too long.
Tia!
Could you perhaps use a bit string? https://www.postgresql.org/docs/7.3/static/datatype-bit.html. (Set the nth bit to 1 when the nth attribute would have been "true")
Depends how you wants to access them in normal usage.
Do you need to access one of this value at time, in this case JSONB is a really good way, really easy and quick to find a record, or do you need to get all of them in one call, in this case Bit String Types are the best, but you need to be really careful around, order and transcription for writing and reading..
Any of the options will do, depending on your circumstances. There is little need to optimise storage if you have only 150 values. Unless, of course there can be a very large number of these sets of 150 values or you are working in a very restricted environment like an embedded system (in which case a full-blown database client is probably not what you're looking for).
There is no definite answer here, but I will give you a few guidelines to consider. As from experience:
You don't want to have an anonymous string of values that is interpreted in code. When you change anything later on, your 1101011 or 0x12f08a will be rendered an fascinatingly enigmatic problem.
When the number of your fields starts to grow, you will regret if they are all stored in a single cell on a single row, because you will either be developing some obscure SQL or transforming a larger-than-needed dataset from the server.
When you feel that boolean values are really not enough, you start to wonder if there is a possibility to store something else too.
Settings and environmental properties are seldom subject to processor or data intensive processing, so follow the easiest path.
As my recommendation based on the given information and some educated guessing, you'll probably want to store your information in a table like
string key | integer set_idx | string value
---------------------------------------------------------
use.the.force | 1899 | 1
home.directory | 1899 | /home/dvader
use.the.force | 1900 | 0
home.directory | 1900 | /home/yoda
Converting a 1 to boolean true is cheap, and if you have only one set of values, you can ignore the set index.
I am trying to test out BigQuery but am getting stuck on creating a table from data stored in google cloud storage. I am able to reduce the data down to just one value, but it is not making sense.
I have a text file I uploaded to google cloud storage with just one integer value in it, 177790884
I am trying to create a table via the BigQuery web UI, and go through the wizard. When I get to the schema definition section, I enter...
ID:INTEGER
The load always fails with...
Errors:
File: 0 / Line:1 / Field:1: Invalid argument: 177790884 (error code: invalid)
Too many errors encountered. Limit is: 0. (error code: invalid)
Job ID trusty-hangar-120519:job_LREZ5lA8QNdGoG2usU4Q1jeMvvU
Start Time Jan 30, 2016, 12:43:31 AM
End Time Jan 30, 2016, 12:43:34 AM
Destination Table trusty-hangar-120519:.onevalue
Source Format CSV
Allow Jagged Rows true
Ignore Unknown Values true
Source URI gs:///onevalue.txt
Schema
ID: INTEGER
If I load with a schema of ID:STRING it works fine. The number 177790884 is not larger than a 64 bit signed int, I am really unsure what is going on.
Thanks,
Craig
Your input file likely contains a UTF-8 byte order mark (3 "invisible" bytes at the beginning of the file that indicate the encoding) that can cause BigQuery's CSV parser to fail.
https://en.wikipedia.org/wiki/Byte_order_mark
I'd suggest Googling for a platform-specific method for view and remove the byte order mark. (A hex editor would do.)
The issue is definitely with file's encoding. I was able to reproduce error.
And then "fixed" it by saving "problematic" file as ANSI (just for test) and now it was loaded successfully.
I am working on a database that (hopefully) will end up using a primary key with both numbers and letters in the values to track lots of agricultural product. Due to the way in which the weighing of product takes place at more than one facility, I have no other option but to maintain the same base number but use letters in addition to this base number to denote split portions of each lot of product. The problem is, after I create record number 99, the number 100 suddenly floats up and underneath 10. This makes it difficult to maintain consistency and forces me to replace this alphanumeric lot ID with a strictly numeric value in order to keep it sorted (which I use "autonumber" as the data type). Either way, I need the alphanumeric lot ID, and so having 2 ID's for the same lot can be confusing for anyone inputting values into the form. Is there a way around this that I am just not seeing?
If you're using query as a data source then you may try to sort it by string converted to number, something like
SELECT id, field1, field2, ..
ORDER BY CLng(YourAlphaNumericField)
Edit: you may also try Val function instead of CLng - it should not fail on non-numeric input
Why not properly format your key before saving ? e.g: "0000099". You will avoid a costly conversion later.
Alternatively, you could use 2 fields as the composite PK. One with the Number (as Long) and one with the Location (as String).
I have some content in a file on which I must generate statistics such as how many of records are of type - 1, type - 2 etc. Number of types can change and is unknown to the code until file arrives. In a SQL system, I can do this using COUNT and GROUP BY clause. But I am not sure if I can do this using SYNCSORT or COBOL program. Would anyone here have an idea on how I can implement 'GROUP BY' type query on a file using SYNCSORT.
Sample Data:
TYPE001 SUBTYPE001 TYPE01-DESC
TYPE001 SUBTYPE002 TYPE01-DESC
TYPE001 SUBTYPE003 TYPE01-DESC
TYPE002 SUBTYPE001 TYPE02-DESC
TYPE002 SUBTYPE004 TYPE02-DESC
TYPE002 SUBTYPE008 TYPE02-DESC
I want to get the information such as TYPE001 ==> 3 Records, TYPE002 ==> 3 Records. What the code doesn't know until runtime is the TYPENNN value
You show data already in sequence, so there is no need to sort the data itself, which makes SUM FIELDS= with SORT a poor solution if anyone suggests it (plus code for the formatting).
MERGE with a single input file and SUM FIELDS= would be better, but still require the code for formatting.
The simplest way to produce output which may suit you is to use OUTFIL reporting functions:
OPTION COPY
OUTFIL NODETAIL,
REMOVECC,
SECTIONS=(1,7,
TRAILER3=(1,7,
' ==> ',
COUNT=(M10,LENGTH=3),
' Records'))
The NODETAIL says "remove all the data lines". The REMOVECC says "although it is a report, don't use printer-control characters on position one of the output records". The SECTIONS says "we're going to use control-breaks, and here they (it in this case) are". In this case, your control-field is 1,7. The TRAILER3 defines the output which will be produced at each control-break: COUNT here is the number of records in that particular break. M10 is an editing mask which will change leading zeros to blanks. The LENGTH gives a length to the output of COUNT, three is chosen from your sample data with sub-types being unique and having three digits as the unique part of the data. Change to whatever suits your actual data.
You've not been clear, and perhaps you want the output "floating" (3bb instead of bb3, where b represents a blank)? That would require more code...