a) specific content inside the files (text, pdf, html mostly)
b) specific substring in the file name
and when I specify these conditions, I find that it takes a long time. I can understand when it takes a longer time for finding inside all files (when no name filter is specified) but when it takes longer time even when substring occuring in the name is provided, I have the following question.
a) Does the order of the conditions matter ? e.g. If I give the substring in the name condition first followed by the condition to search inside the file, will it help as the first condition narrows the results (files only with specific names or substrings in names) for the second condition (searching the file contents) to search. (Sometimes I even use subclauses to find content inside the file based on AND/OR or various combinations thereof).
b) When I use the find panel repeatedly within the same session on the same set of files/folders to find files with different conditions, does Directory Opus 'cache or remember' the folder or file contents to make the process faster during the subsequent finds.
Yes, the order does matter. You should do the quickest checks first.
If you search for "name and content", in that order, then Opus will check the names first and the contents second. It will only check the contents if the name matches.
If you search for "content and name" then it will be slower because Opus will first check the contents and only check the names afterwards. It's much quicker to check the filename than it is to read through the contents of a file, so checking the contents before the name will be much slower.
Important note: Opus currently does a literal search of the file contents. It doesn't understand the markup/formating data within PDF or HTML files and will only find strings inside them if they are uninterrupted.
e.g. If you search for "fluffy kittens" and an HTML file contains "fluffykittens" then Opus won't consider it a match.
b)
Opus itself does not cache any find data. The OS/filesystem will often cache a lot of data (including file contents), though, so repeated Find operations on the same folder are often much quicker (even if they search contents). How much gets cached depends on the amount of data and free memory (and version of Windows).
If you want to use indexed searching (where the file contents only need to be searched once), which also properly searches PDF and HTML file contents, then you might want to try Google Desktop Search which Opus will hook into if it is installed. You get a GDS tab in the Find panel and all content searching is done via a a database/index so it's very fast (once that database has been created).