Pasting into a photoshop channel/layer/alpha mask

All I want to do is paste into the channel mask of a layer, this is where GIMP has a big win.  Right click, then select create greyscale copy of layer as mask.  Yay, exactly what I want to do.

Photoshop has an all or nothing approach, reveal all or reveal none, to create an all black or all white mask, I then have to paste to the mask, but to paste to the mask I have to enable/make it visible first.

The easiest way:

Alt-Click the layer mask. (To enable direct editing of the layer mask)
Ctrl-V to paste into the layer mask.

The slightly more convoluted way:

Click on the channels list, then click on the eye next to mask layer to make it visible/editable.
Ctrl-V to paste into the layer mask.

Further, if you want to automate the paste into mask, you need to use Ctrl-Shift-V.

Netsupport Mac Client CPU Issue

Netsupport is great.  It allows you to remote access, and control other machines on your network.  Of course there are other ways to do it eg RDP, and VNC, but netsupport nicely ties it all together and makes it very easy.

I did have an issue however, on the Mac, I just wanted to install the Netsupport Manager,  ie I just wanted to control other machines, and not be controlled.  During the installation there didn't seem to be any options to not install the client, but as I checked the 'control and manage only' option (or words to that effect) and assumed the client wouldn't be installed.  

Not only was the client installed, but when the machine is idle. The Netsupport Client processing is running, and taking up about 8-10% CPU all the time.  As I have a reasonably decent machine (OS X 10.9.3, 2.3GHz i7, 16GB RAM) this CPU use is hardly noticeable, but it really bugged me.

Killing the process wont work as it's restarted automatically, so I had to look a little deeper.

The secret is in

/Library/Preferences/NetSupport/NetSupportManager

There are 2 files:

ns-login.sh
ns-logout.sh

In the login file I just commented out the line where the monitoring process is started:

#${SESSIOND} "*" /s &

This stops the client from being started, and restarted.  The Netsupport Manger still works, ie connects and Controls other machines, but I dont have the Client eating 10% of my CPU now.

MySQL Disable Foreign Key Checks

What and Why

Here are some test results regarding foreign key checks in mysql, and what actually happens to the data, when you change the relation type, eg CASCADE, SET NULL, RESTRICT, and NO ACTION.


I basically want to check whether foreign keys are processed on the table after the key checks are reenabled, or they are ignored completely, or if there is some other vooodoo that happens.

Method

I setup 2 Tables, T1 and T2, T1 has a primary key (id) and T2 has a foreign key (ref) which points to T1.id.

For the test I just did updates to the id in T1, and deleted a row in T1, and watched what happened to the data in T2, for each of the FK relations types.

The code used to disable the foreign key checks is:

SET foreign_key_checks = 0;
-- UPDATE `test1` set id=13 where id = 3;
DELETE FROM `test1` WHERE id = 3;
SET foreign_key_checks = 1;

I commented out the delete or update line as appropriate.
and then reset the tables after each test.

Results

Normal Operation
================
CASCADE on update = both records updated
CASCADE on delete = both records deleted
SET NULL on delete = row deleted and ref set to null
SET NULL on update = row updated and ref set to null
RESTRICT on delete = delete prevented
RESTRICT on update = update prevented
NO ACTION on update = update prevented
NO ACTION on delete = delete prevented

Disable FK Checks
=================
CASCADE on update = row updated and leaves dangling ref
CASCADE on delete = row deleted and leaves dangling ref
SET NULL on update = row updated and leaves dangling ref
SET NULL on delete = row deleted and leaves dangling ref
RESTRICT on update = row updated and leaves dangling ref
RESTRICT on delete = row deleted and leaves dangling ref
NO ACTION on update = row updated and leaves dangling ref
NO ACTION on delete = row deleted and leaves dangling ref

Conclusion

The most obvious conclusion, is that disabling foreign key checks as a  part of the update or delete process can leave invalid foreign keys in the database.  While there might be good reasons for doing this, the chance that the data will be left in an inconsistent state is very high.