I was one of the indexers who seized on the opportunity to help get these indexes online, because they are an essential resource that was formerly all but inaccessible to most of the people who wanted to use it. So I am familiar with the records, and I understand their structure. I decided to do sample searches using a not-too-common Irish surname, Rowley. I selected the database 'Ireland, Civil Registration Indexes, 1845-1958', then Advanced search, and searched for the surname Rowley, with the 'exact match' ticked. It gave me 2124 results. The search boxes and drop-down menus are on the left, and one of the drop-downs is 'Event'. from this I selected Births, but the search still returned 2124 results, and the same thing happened when I selected 'marriages', 'deaths' or 'residence', all with the 'match all exactly' box ticked. Hmm. Something isn't working here.
Back to the birth search for a moment; the first of my 2124 results was for a birth in 1826 - nearly 40 years before the start of registration. It is, of course, a death where the age at death is recorded in the indexes, and the year of birth has been estimated from this. Scrolling through the results, the first 84 were of this kind, death entries with an estimated birth date, not actual birth registrations. The 85th result was for a death with no estimated birth year, and therefore by no stretch of the imagination what you would expect to get from a birth search. Oh dear. I narrowed the search to Thomas Rowley, and this returned 119 results; when I selected 'Births' from the drop-down menu, I still got 119 results; 26 deaths with estimated birth years, then 27 marriages, and finally 66 actual birth entries. So I was able to find out, eventually, how many Thomas Rowley births were registered in Ireland 1845-1958, but I had to click through the results a page at a time to get there, at 20 results a page. I'm glad it wasn't Patrick Murphy - there are 18089 of them. Changing the filter to marriage, death or residence made no difference whatever.
I tried a different kind of search, filtering by place. There are lots of Rowleys in Co Sligo, so I searched for the surname Rowley with 'Sligo' in the 'Place' box, both ticked for an exact match, and got four results, all from 1957 or 1958, four births from Sligo registration district, and a marriage in Tubbercurry district, which is in the county. When I repeated the search, but with the exact place search un-ticked, I got 1895 results from all over Ireland. It is not at all obvious how the non-exact place search works, because it filters out 229 hits from my original search, but still includes results from Dublin, Belfast and other places that are nowhere near Sligo. If I change the place filter to Tubbercurry, I get no results at all, whether ticked for an exact search or not, not even the 1958 marriage. If I change it to Tobercurry, the more usual spelling, I get 50 hits for both kinds of search. I could go on, but I think this enough to show that these searches do not work properly, and I doubt if it the problem is confined to a single record set.
There is one more thing I want to highlight about the Irish records. The advanced search facility looks as though you can search for relatives, but with one exception, you can't. I know this, because I have seen the printed indexes from which they are constructed. The Civil Registration indexes are exactly that - indexes. You can select 'Spouse' from the 'Relationship' drop-down and put a surname in the 'Mother's maiden name box' and get results back, but only birth from the 1920s and later, when the mother's maiden name is in the indexes. You can select 'Spouse' from the relationship drop-down, but if you put anything at all in the boxes, you will get no results. This is because it is impossible to get this information from the Civil Registration indexes, they don't contain enough detail, so it is misleading to suggest that this search is feasible. Perhaps searches like this could be disabled where the database does not support them?