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Merge pull request #163 from snorremd/develop

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Document PGInterval to Duration handling for postgres
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Sean Corfield 2021-04-25 13:32:48 -07:00 committed by GitHub
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doc/tips-and-tricks.md
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@ -202,6 +202,54 @@ In addition, if you want `java.time.Instant`, `java.time.LocalDate`, and `java.t
`next.jdbc.date-time` also includes functions that you can call at application startup to extend `ReadableColumn` to either return `java.time.Instant` or `java.time.LocalDate`/`java.time.LocalDateTime` (as well as a function to restore the default behavior of returning `java.sql.Date` and `java.sql.Timestamp`).
### Working with Interval
Postgres has a nonstandard SQL type Interval that is implemented in the Postgres driver as the `org.postgresql.util.PGInterval` type.
In many cases you would want to work with intervals as `java.time.Duration` type by default.
You can support `Duration` instances by extending `SettableParameter` to the `java.time.Duration` type.
Conversely you can support converting PGIntervals back to Durations by extending `ReadableColumn` to the `org.postgresql.util.PGInterval` type.
```clojure
(import '[org.postgresql.util PGInterval])
(import '[java.sql PreparedStatement])
(import '[java.time Duration])
(require '[next.jdbc.result-set :as rs])
(require '[next.jdbc.prepare :as p])
(defn ->pg-interval
"Takes a Dudration instance and converts it into a PGInterval
instance where the interval is created as a number of seconds."
[^java.time.Duration duration]
(doto (PGInterval.)
(.setSeconds (.getSeconds duration))))
(extend-protocol p/SettableParameter
;; Convert durations to PGIntervals before inserting into db
java.time.Duration
(set-parameter [^java.time.Duration v ^PreparedStatement s ^long i]
(.setObject s i (->pg-interval v))))
(defn <-pg-interval
"Takes a PGInterval instance and converts it into a Duration
instance. Ignore sub-second units."
[^org.postgresql.util.PGInterval interval]
(-> Duration/ZERO
(.plusSeconds (.getSeconds interval))
(.plusMinutes (.getMinutes interval))
(.plusHours (.getHours interval))
(.plusDays (.getDays interval))))
(extend-protocol rs/ReadableColumn
;; Convert PGIntervals back to durations
org.postgresql.util.PGInterval
(read-column-by-label [^org.postgresql.util.PGInterval v _]
(<-pg-interval v))
(read-column-by-index [^org.postgresql.util.PGInterval v _2 _3]
(<-pg-interval v)))
```
### Working with Enumerated Types
PostgreSQL has a SQL extension for defining enumerated types and the default `set-parameter` implementation will not work for those. You can use `next.jdbc.types/as-other` to wrap string values in a way that the JDBC driver will convert them to enumerated type values: