I research the Irish Family History Foundation's database. It contains 12,800,000 surviving rcds for abt 70% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800. Cos. Donegal and Derry were recently added to the database.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 30%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
Note 4 - The National Library of Ireland (NLI) has microfilms of parish church rcds.
For And(rew) Mackey B 1822 +/- 4 yrs, Co. Kilkenny, with the father's forename unknown, I found 0 rcds.
For Johanna Newman B 1831 +/- 4 yrs, somewhere in Ireland, ditto, I found ditto.
For And(rew) Mackey M 1866 +/- 1 yr, somewhere in Ireland, I found 2 rcds: 1866 Antrim, and 1867 Kilkenny.
For Johanna Newman M ditto, I found NO rcds matching those for Andrew.
For Thomas Mackey B 1867 +/- 1 yr, somewhere in Ireland, with a father named Andrew, I found 0 rcds.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.