Fixing a dripping tap

Fixing a dripping tap. Its not a big problem.

Of course its not a big problem, its only a paragraph in my DIY book. Turn off mains, unscrew cover, remove headgear nut, remove washer, replace washer, reassemble, turn on mains. There, in one line. How can that be a big problem?

Well, perhaps the cover is corroded on. Never mind, I've got the foresight to borrow some PlusGas from a friend - stronger than WD40, this breaks anything. Eventually. After four sprayings and some leverage with a molegrips its loose and I can lift it up. Now, remove headgear nut. Yeah, but that needs a thin spanner, and the only thin spanners I've got are too small. Never mind, I can take the cross-shaped handle off and remove the cover completely. If I can get the grub screw out. Several sprayings of PlusGas and some GT85 for variety its out. Phew. But the handle doesnt budge. I fill the room with PlusGas vapours and decide ten minutes ago would have been a good time to open the window.

Okay, handle is off, cover is off, and I am presented with a corroded misshapen lump of metal like something recently retrieved from the wreck of the Titanic. I chip off some corrosion to reveal the headgear nut. A small amount of PlusGas and the application of a 3/8 spanner and its off, revealing the crumbly remains of what used to be a washer. Part of it falls off, part of it is attached to the spindle by a small nut.

I soak the nut and spindle in a small pool of PlusGas, then attack it with a spanner and mole grips. It gives way eventually. Now I have the parts of the washer I need.

So down to B+Q where of course they have nothing that looks like the pieces I've extracted. Nor do they have anyone who can tell me if any of the other rubber and vaguely circular pieces with or without holes will act as replacement. I buy three packs of misc washers and valve seats and head home.

The valve seat on the tap looks okay, so I just decide to stick a new washer on the jumper plate. The threads on the small nut are in no fit state, so some persuasion (aka mole grips) is necessary. I put the tap all back together. Down the cellar. Mains on. Run upstairs. Its. Not. Dripping. Hoo. Ray.

Django indexed search...

Zope has its 'catalog'. Any object can register with the catalog, and it gets indexed, then code can ask the catalog for a search and get a list of objects back.

How do we do something like this in Django? There are some existing ideas out there, for example Merquery. That post also has some links to other ideas for python-based text searching. Merquery is pretty much just an idea at the moment, and the examples are SQLObject oriented. What might a Django indexed search system look like? Here's some ideas:

• Every searchable model class has a method to index or re-index instances of it in the index database
• Index updates happen automatically on save() or other updates of the instance
• If a django object is deleted, remove the entry in the index
  
• If you change the object directly with SQL, its your job to call the re-index method
• There must be a way to re-build the index from scratch. This would iterate over all indexable objects.
• Comes with methods for indexing standard fields (minimally CharField and TextField) but extensible to other fields - imagine indexing PDF files...
  

Okay, so we've built our index and hopefully it keeps up-to-date. What about searches? What would be nice?

• Ability to search over multiple classes - for example blog texts and blog comments.
• Ability to restrict search to some or all fields.
  
• Ability to use Fields in queries - so you could search for anyone with firstName Fred and lastName not Smith.
• Ability to specify an ordering - by relevance, or some date field.
• Get from the search result back to the Django object. HyperEstraier stores a user-defined URI with each document it indexes, and this would have to map to Django objects. Best I can think of at the moment is a URI which is a string concatenation of model and id.
  

Perhaps we should have an IndexedModel class that extends the usual Django Model class:

class Blog(IndexedModel):
  name=CharField()
  body=TextField()

by default this will index all fields that it knows how to index. This can be controlled with an inner class in the same way as the Admin inner class does:

class Blog(IndexedModel):
  class Indexer:
      fields=("name","body",)
  name=CharField()
  body=TextField()
  secret=TextField()
  moo=CowField()

This would index the name and body fields, but not the secret field, nor the moo field, since it doesn't know how to deal with CowField types.

I haven't yet thought how to organise the search end of things... Comments on all of this welcome!

B