This turns out to be more involved, related to particular field combinations. The content model of the project I'm using this on at the moment is very minimal so I can't try everything, but to start:
In all cases the search term is "the"
Assuming anyone replicates this, your specific numbers may change, obviously, since this is dependent upon how many actual matches you have in your data. Just for reference, I've got about 2000 items at the moment.
- Searching post titles with no limit always returns nothing.
- Searching post titles with limit 10 returns 5 results.
- Searching post titles with limit 25 returns 11 results.
- Searching post titles with limit 50 returns 23 results.
- Searching post titles with limit 100 returns 32 results.
Note that each time we increase the limit(beyond 10), we get a number of results that should've been possible with the lower limit.
- Searching post URLs with "no limit" also always returns nothing.
- Post URL searches exhibit similar behavior to the numbered limits for titles.
- Searching post content with any of the limit options(including none) returns 959 items
- This is especially weird, so I tried a another term "will", and the behavior is the same. (With different number of matches.)
I don't have much data in the post excerpts, but there's a term I do know appears several times, so using it:
- Searching post excerpts with no limit returns nothing
- Using numerical limits, I still get nothing until set to 50(1 result) and 100(2 results), which obviously makes no sense.
- Additionally, I know the term appears a lot more often than that, so there's still instances that are being outright ignored.
I have no comment or meta field data at the moment, so can't try those.
The behavior at least partially duplicates on a separate installation(though too small to draw much conclusions from), so hopefully I'm not completely wasting my time here documenting a case-specific glitch. Trying to find a larger install to try things out on for confirmation.