Don't look up the type oid for types that never use it #168
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Getting function argument type oids can be surprisingly expensive; one
Promscale benchmark measures it as taking over 10% of runtime.
Fortunately, most types do not actually make use of this information,
and the `getarg_type()` call can be optimized out if this fact is
known. This commit adds an opt-in method for declaring that a type does
not make use of the `typeoid` in `from_datum()`, and updates
`pg_getarg()` to make use of this information.
This commit makes the following changes:
1. It adds a `const` boolean to `FromDatum` called `NEEDS_TYPID`. This
boolean is defaulted to `true`. Types that never use the `typeoid`
parameter to `from_datum()` can override this to `false`.
2. `pg_getarg()` updated to look at `T::NEEDS_TYPID` before calling
`get_getarg_type()`. If `T::NEEDS_TYPID == true` it calls
`get_getarg_type()` like it currently does for all types; if it is
`false` it instead passes `InvalidOid` as the (unused) `typeoid`
argument to `from_datum()`.
3. It edits a number of built in types to make use of this
optimization.
Since this feature is both opt-in and backwards compatible, it should
not break any downstream users.
This was referenced Sep 24, 2021
Merged
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Getting function argument type oids can be surprisingly expensive; one Promscale benchmark measures it as taking over 10% of runtime (@cevian should have more info). Fortunately, most types do not actually make use of this information, and the
getarg_type()call can be optimized out if this fact is known. This commit adds an opt-in method for declaring that a type does not make use of thetypeoidinfrom_datum(), and updatespg_getarg()to make use of this information.This commit makes the following changes:
constboolean toFromDatumcalledNEEDS_TYPID. This boolean is defaulted totrue. Types that never use thetypeoidparameter tofrom_datum()can override this tofalse.pg_getarg()updated to look atT::NEEDS_TYPIDbefore callingget_getarg_type(). IfT::NEEDS_TYPID == trueit callsget_getarg_type()like it currently does for all types; if it isfalseit instead passesInvalidOidas the (unused)typeoidargument tofrom_datum().Since this feature is both opt-in and backwards compatible, it should not break any downstream users.