Cursors
Shawnda Regal
All access to cursors in PL/pgSQL goes through cursor variables, which are always of the special data type refcursor. One way to create a cursor variable is just to declare it as a variable of type refcursor. Another way is to use the cursor declaration syntax, which in general is:
PL/pgSQL functions can return cursors to the caller. This is useful to return multiple rows or columns, especially with very large result sets. To do this, the function opens the cursor and returns the cursor name to the caller (or simply opens the cursor using a portal name specified by or otherwise known to the caller). The caller can then fetch rows from the cursor. The cursor can be closed by the caller, or it will be closed automatically when the transaction closes.
Prior to PostgreSQL 16, bound cursor variables were initialized to contain their own names, rather than being left as null, so that the underlying portal name would be the same as the cursor variable's name by default. This was changed because it created too much risk of conflicts between similarly-named cursors in different functions.
What is the reason for this level of insane hatred? Has some 'noted authority' issued a fatwa against cursors? Does some unspeakable evil lurk in the heart of cursors that corrupts the morals of children or something?
EDIT: let me be more precise: I understand that cursors should not be used instead of normal relational operations; that is a no-brainer. What I don't understand is people going waaaaay out of their way to avoid cursors like they have cooties or something, even when a cursor is a simpler and/or more efficient solution. It's the irrational hatred that baffles me, not the obvious technical efficiencies.
The "overhead" with cursors is merely part of the API. Cursors are how parts of the RDBMS work under the hood. Often CREATE TABLE and INSERT have SELECT statements, and the implementation is the obvious internal cursor implementation.
In some circles, the relational joins are a mystery, and folks will write nested cursors rather than a simple join. I've seen truly epic nested loop operations written out as lots and lots of cursors. Defeating an RDBMS optimization. And running really slowly.
Simple SQL rewrites to replace nested cursor loops with joins and a single, flat cursor loop can make programs run in 100th the time. [They thought I was the god of optimization. All I did was replace nested loops with joins. Still used cursors.]
I try to use an ORM layer as much as possible. But that has two purposes. First, the cursors are managed by the ORM component. Second, the SQL is separated from the application into a configuration file. It's not that the cursors are bad. It's that coding all those opens, closes and fetches is not value-add programming.
Please note that cursors are the SLOWEST way to access data inside SQL Server. The should only be used when you truly need to access one row at a time. The only reason I can think of for that is to call a stored procedure on each row. In the Cursor Performance article I discovered that cursors are over thirty times slower than set based alternatives.
This statement may be true under many circumstances, but as a blanket statement it's problematic. For example, I've made good use of cursors in situations where I want to perform an update or delete operation affecting many rows of a large table which is receiving constant production reads. Running a stored procedure which does these updates one row at a time ends up being faster than set-based operations, because the set-based operation conflicts with the read operation and ends up causing horrific locking problems (and may kill the production system entirely, in extreme cases).
Cursors tend to be used by beginning SQL developers in places where set-based operations would be better. Particularly when people learn SQL after learning a traditional programming language, the "iterate over these records" mentality tends to lead people to use cursors inappropriately.
Outside of the performance (non)issues, I think the biggest failing of cursors is they are painful to debug. Especially compared to code in most client applications where debugging tends to be comparatively easy and language features tend to be much easier. In fact, I contend that nearly anything one is doing in SQL with a cursor should probably be happening in the client app in the first place.
As to your question, while there are certainly situations where a cursor may be called for, in my experience developers decide that a cursor "must" be used FAR more often than is actually the case. The chance of someone erring on the side of too much use of cursors vs. not using them when they should is MUCH higher in my opinion.
I knew of some performance reasons back in the SQL 7 days, but do the same issues still exist in SQL Server 2005? If I have a resultset in a stored procedure that I want to act upon individually, are cursors still a bad choice? If so, why?
What you are really doing is attempting to force set-based technology into non-set based functionality. And, in all fairness, I should point out that cursors do have a use, but they are frowned upon because many folks who are not used to using set-based solutions use cursors instead of figuring out the set-based solution.
I wouldn't call it "bad practice" to use cursors, but they do consume more resources on the server (than an equivalent set-based approach) and more often than not they aren't necessary. Given that, my advice would be to consider other options before resorting to a cursor.
There are several types of cursors (forward-only, static, keyset, dynamic). Each one has different performance characteristics and associated overhead. Make sure you use the correct cursor type for your operation. Forward-only is the default.
This library contains computer mouse cursors for Microsoft Windows systems.There are two types of cursors supported directly by Windows operating systems:static (.cur) and animated (.ani). Both types are present in this library.Learn how to download cursors.
If you change your cursors frequently, consider using a free tool that allows you tochange cursor from Windows Explorer context menu. Beside changing cursors one by one, the tool also allows exporting and importing cursor schemes.
If you do not want to install any software, just click on Control Panel in Start menu, then double-click the Mouse icon andswitch to Pointer tab. Here you can change the cursors used by Windows in differentsituations to the downloaded ones.
Important: only cursor authors or copyright holders may add cursor to the library.If you are using pictures downloaded from internet to create cursors, you must make sure the author of the picturesallows this use of their work.
Important: always create 32x32 pixels cursors unless you have a serious reason not to. While it is possible to make cursors of non-standard size, Windows will automatically resample them decreasing image quality.
over the last couple days, i have a few users complain that they have been having issues with their mouse cursor either not showing, disappearing or in some cases showing multiple mouse cursors. Has anyone else experienced similar issues and have a permanent fix for them? I think if i have the users check the box for Lock the keyboard and mouse on the logmein toolbar that seems to help.
If the data is relatively slow then generate an array to store all of your points (same number as displayed on your chart) and for each new point acquired, rotate the array and replace the last element with the new point and update the waveform graph. Then you can have the cursors you want, just a bit of extra data manipulation.
Apparently it needs a session with the cursors theme saved to keep them. The only file I have now in the /.cache/sessions dir is xfce4-session-unni:0 (unni being my username) along with a thumbs dir.
What I ended up doing is [Shift] + [Alt] clicking before the first word, scrolling down, [Shift] + [Alt] clicking before the last word to set cursors there, typing TEXT(", then doing the same thing off to the right leaving a large amount of whitespace to type the ending. Then highlight the strings and from the top, click on Edit > Advanced > Delete Horizontal Whitespace. You might need to do it twice, but it worked for me.
I also noticed that using UI.create_cursor the cursor does not scale correctly on Windows 10 with one monitor (4K) set to 175%, and another monitor set to 100%. The build in cursors scale correctly as does the CURSOR_PENCIL = 632
SketchUp only supports up to 150% display scaling (aka scaled resolution on Mac.)
But with regard to cursors and toolbar buttons, the image must be a vector SVG (or PDF on Mac,) in order to be correctly and precisely scaled. (Raster image formats can get blurry.)
When using multiple cursors on a single line, performance dramatically slows down as the line becomes longer. This gets to the point where my entire PC will freeze for multiple seconds after every input.
The cursors are indeed installed in the /usr/share/icons folder. User specific cursor themes can be installed in /.local/share/icons folder. You might have got confused because of all those icon themes there.
Create a folder named cursors that folder. You'll put your cursors files in this folder. The cursors should be named following specific naming guide line (Check the linked Ubuntu forum page for the guideline). You can also find the names from the default cursor theme DMZ-White.
If I were to do it all over again, I might consider just using the UWidgetInteractionComponent and faking all of the picking up and placing of UI stuff. Even Smash Bros used 3D cursors and 3D tokens for most of their games.
If you'd like to change the modifier key for applying multiple cursors to Cmd+Click on macOS and Ctrl+Click on Windows and Linux, you can do so with the editor.multiCursorModifier setting. This lets users coming from other editors such as Sublime Text or Atom continue to use the keyboard modifier they are familiar with.
df19127ead