I would like to write a function module that returns a range table. Is that possible and if so, how?
The structure of a typed range is like this :
**Name** **Type**
SIGNT VARV_SIGN
OPTION TVARV_OPTI
LOW your-type
HIGH your-type
You can create this structure in the dictionary, as well as a table of those, and then use it in the FM signature.
Also, a generic structure already exists : RSDSSELOPT (along with a table type RSELOPTION).
Related
Can someone advise me on the SQL data type that should be used for a DICOM UID, 1.2.840.113986.3.2702661254.20150220.144310.372.4424 as a sample. I would like to use it as a primary key as well.
There are two options available here- either use a less-than-ideal data type which already exists, of which "text" is almost certainly the best option, or implement a custom data type for this particular type of data.
While the best built-in option is "text", looking at the example provided, you would likely get significant performance and space benefits from using a custom data type, though it would require writing code to implement it.
A final option to consider is to use a surrogate key for that data. To do this, you would build a table which contains a "bigserial" column and then a "text" column. The "text" column would hold the long form of the value as you have it shown above and the "bigserial" column would provide an integer (64bit with bigserial, 32 bit if you use "serial" instead) which you would then use in all of your tables, instead of the long form.
As title shown, when reading the manul, I found type record type and row type, which are both composite type. However, I want to figure out their difference.
They're similar once defined but tend to have different use cases.
A RECORD type has no predefined structure and is typically used when the row type might change or is out of your control, for example if you're referencing a record in a FOR LOOP.
ROWTYPE is predefined of a particular table row structure and thus if anything deviates from that structure you will get runtime errors.
It all depends what you're trying to achieve.
For cursor loops I use a RECORD>
For more information:
http://www.postgresql.org/docs/current/static/plpgsql-declarations.html
Is it possible to use the %TYPE and array together?
CREATE FUNCTION role_update(
IN id "role".role_id % TYPE,
IN name "role".role_name % TYPE,
IN user_id_list "user".user_id % TYPE[],
IN permission_id_list INT[]
)
I got syntax error by this, but I don't want to duplicate any column type, so I want to use "user".user_id % TYPE instead of simply INT because then it is easier to modify any column type later.
As the manual explains here:
The type of a column is referenced by writing table_name.column_name%TYPE. Using this feature can sometimes help make a function independent of changes to the definition of a table.
The same functionality can be used in the RETURNS clause.
But there is no simple way to derive an array type from a referenced column, at least none that I would know of.
About modifying any column type later:
You are aware that this type of syntax is only a syntactical convenience to derive the type from a table column? Once created, there is no link whatsoever to the table or column involved.
It helps to keep a whole create script in sync. But id doesn't help with later changes to live objects in the database.
Related answer on dba.SE:
Array of template type in PL/pgSQL function using %TYPE
Using referenced types in function's parameters has no sense (in PostgreSQL), because its translated intermediately to actual types, and it is stored as actual types. Sorry, PostgreSQL doesn't support this functionality - something different is using referenced types inside function, where actual type is detected every first time execution in session.
I have been implementing user defined types in Postgresql 9.2 and got confused.
In the PostgreSQL 9.2 documentation, there is a section (35.11) on user defined types. In the third paragraph of that section, the documentation refers to input and output functions that are used to construct a type. I am confused about the purpose of these functions. Are they concerned with on-disk representation or only in-memory representation? In the section referred to above, after defining the input and output functions, it states that:
If we want to do anything more with the type than merely store it,
we must provide additional functions to implement whatever operations
we'd like to have for the type.
Do the input and output functions deal with serialization?
As I understand it, the input function is the one which will be used to perform INSERT INTO and the output function to perform SELECT on the type so basically if we want to perform an INSERT INTO then we need a serialization function embedded or invoked in the input or output function. Can anyone help explain this to me?
Types must have a text representation, so that values of this type can be expressed as literals in a SQL query, and returned as results in output columns.
For example, '2013-20-01' is a text representation of a date. It's possible to write VALUES('2013-20-01'::date) in a SQL statement, because the input function of the date type recognizes this string as a date and transforms it into an internal representation (for both using it in memory and storing to disk).
Conversely, when client code issues SELECT date_field FROM table, the values inside date_field are returned in their text representation, which is produced by the type's output function from the internal representation (unless the client requested a binary format for this column).
This is probably a super simple question, but I'm struggling to come up with the right keywords to find it on Google.
I have a Postgres table that has among its contents a column of type text named content_type. That stores what type of entry is stored in that row.
There are only about 5 different types, and I decided I want to change one of them to display as something else in my application (I had been directly displaying these).
It struck me that it's funny that my view is being dictated by my database model, and I decided I would convert the types being stored in my database as strings into integers, and enumerate the possible types in my application with constants that convert them into their display names. That way, if I ever got the urge to change any category names again, I could just change it with one alteration of a constant. I also have the hunch that storing integers might be somewhat more efficient than storing text in the database.
First, a quick threshold question of, is this a good idea? Any feedback or anything I missed?
Second, and my main question, what's the Postgres command I could enter to make an alteration like this? I'm thinking I could start by renaming the old content_type column to old_content_type and then creating a new integer column content_type. However, what command would look at a row's old_content_type and fill in the new content_type column based off of that?
If you're finding that you need to change the display values, then yes, it's probably a good idea not to store them in a database. Integers are also more efficient to store and search, but I really wouldn't worry about it unless you've got millions of rows.
You just need to run an update to populate your new column:
update table_name set content_type = (case when old_content_type = 'a' then 1
when old_content_type = 'b' then 2 else 3 end);
If you're on Postgres 8.4 then using an enum type instead of a plain integer might be a good idea.
Ideally you'd have these fields referring to a table containing the definitions of type. This should be via a foreign key constraint. This way you know that your database is clean and has no invalid values (i.e. referential integrity).
There are many ways to handle this:
Having a table for each field that can contain a number of values (i.e. like an enum) is the most obvious - but it breaks down when you have a table that requires many attributes.
You can use the Entity-attribute-value model, but beware that this is too easy to abuse and cause problems when things grow.
You can use, or refer to my implementation solution PET (Parameter Enumeration Tables). This is a half way house between between 1 & 2.