Re: [Zope] Combining hits from searching 2 ZCatalogs at once

1 May 2003

      On Wednesday 30 April 2003 08:38 pm, Gordon Lai wrote:
...
Hi,
I'm writing a Python script that searches 2 ZCatalogs
at once with a form-provided query. The first ZCat
contains scanned images of text documents plus their
metadata. The second ZCat contains the OCR text of the
same documents. The searches are written like this:
textresults = context.Text_Catalog(
{'PrincipiaSearchSource': query} )
  ocrresults = context.OCR_Catalog(
{'PrincipiaSearchSource': query} )
Text_Catalog is the primary catalog; it contains more
metadata than in OCR_Catalog and hits on this catalog
are preferred. OCR_Catalog is the secondary catalog;
if I get a hit here (and assuming there's no hit on
its matching document in Text_Catalog), then I want to
find its matching document and add its metadata to
textresults as a new hit. I'll then return the
modified textresults to the calling form.
My question is: How do I add the new hit to
textresults? I tried textresults.append( newhit ), but
I found out that textresults isn't a sequence, it's a
LazyCat class instance. How do I append new items to
this instance?
You don't, but you can get the Catalog to return you "raw" sets which can be 
manipulated or added together with other catalogs. To do this, you must use 
an external method to call methods of the underlying Catalog object directly. 
Catalog.py has a function mergeResults which can be used to turn the raw sets 
into lazy catalog results like usual.

Here is a simple example (external method):

from Products.ZCatalog.Catalog import mergeResults

def queryMultipleCatalogs(request, *zcatalogs):
    results = []
    for zcat in zcatalogs:
        results.append(zcat1._catalog.searchResults(request, _merge=0))
    sorted = request.has_key('sort-on') or request.has_key('sort_on')
    reverse = ((request.get('sort-order','') or 
               request.get('sort_order','')).lower() 
               in ('reverse','descending'))
    return mergeResults(results, sorted, reverse)

The key is passing _merge=0 to searchResults. It then returns a raw result 
set. In the case of a sorted set this should be a standard Python list 
containing three tuples of (sort_key, docid/rid, catalog.__getitem__). These 
could be manipulated however you like. mergeResults can turn them back into 
standard catalog results.

To learn more your best bet is to read the Catalog.py sources and use some of 
the methods in there as I have above.

hth,

-Casey

Re: [Zope] Combining hits from searching 2 ZCatalogs at once

Casey Duncan