Using Postgraphile in nodeJS, how to enable aggregate max of date field? - node.js

Question

I am using postgraphile in NodeJS for graphql API based on Postgresql database. I need to get max(date_field), but postgraphile does not provide that option by default.
How can I enable aggregation of max on a date field?
I want something as follows. But inspection_Date field is not available under max
query Query {
allRooms {
aggregates {
max {
inspection_date
}
}
}
}

Answer 1

Using a slightly modified version of the approach outlined in the defining your own aggregates section of the pg-aggregates readme, you can create a new graphile plugin that uses a hook to modify the existing aggregate specs for "min" and "max" to use a different isSuitableType function that includes temporal types as well as numeric types:
import type { Plugin } from "graphile-build";
import type { AggregateSpec } from "#graphile/pg-aggregates/dist/interfaces";
import type { PgType } from "graphile-build-pg";
const addTemporalAggregatesPlugin: Plugin = (builder) => {
builder.hook(
"build",
(build) => {
const { pgAggregateSpecs } = build;
const isNumberLikeOrTemporal = (pgType: PgType): boolean =>
pgType.category === "N" || pgType.category === "D";
// modify isSuitableType for max and min aggregates
// to include temporal types see: https://www.postgresql.org/docs/current/catalog-pg-type.html
const specs = (pgAggregateSpecs as AggregateSpec[] | undefined)?.map(
(spec) => {
if (spec.id === "min" || spec.id === "max") {
return {
...spec,
isSuitableType: isNumberLikeOrTemporal,
};
}
return spec;
}
);
if (!specs) {
throw Error(
"Please that the pg-aggregates plugin is present and that AddTemporalAggregatesPlugin is appended AFTER it!"
);
}
const newBuild = build.extend(build, {});
// add modified aggregate specs to the build
newBuild.pgAggregateSpecs = specs;
return newBuild;
},
["AddTemporalAggregatesPlugin"],
// ensure this hook fires before other hooks in the pg-aggregates plugin
// that may depend on the "pgAggregatesSpecs" extension.
["AddGroupByAggregateEnumsPlugin"],
[]
);
};
export default addTemporalAggregatesPlugin;
Then just append this new plugin after the pg-aggregates plugin:
postgraphile(pool, "my_schema", {
pluginHook,
appendPlugins: [
PgAggregatesPlugin,
AddTemporalAggregatesPlugin,
],
// ...
})