--On Friday, July 21, 2023 3:32 PM +0000 Maud Parratt Maud.Parratt@bjss.com wrote:
why? to be clear I'm experimenting on a smaller ephemeral test instance with non prod data, so there's no risk to trying things.
The man page spells it out pretty clearly:
index_hash64 { on | off } Use a 64 bit hash for indexing. The default is to use 32 bit hashes. These hashes are used for equality and substring indexing. The 64 bit version may be needed to avoid index collisions when the number of indexed values exceeds ~64 million. (Note that substring indexing generates multiple index values per actual attribute value.) Indices generated with 32 bit hashes are incompatible with the 64 bit version, and vice versa. Any existing databases must be fully reloaded when changing this setting. This directive is only supported on 64 bit CPUs.
I'm assuming that you have substring indices, and given the large size of your database you may start having hash collissions.
You most likely also want to configure olcBkMdbIdlExp, sortvals, and multival if you haven't.
--Quanah