How to call a postgres function with an array of composite type

Question

I am looking for suggestions on how to call a postgres function that has an argument that is an array of composite type. Similar questions have been asked but I have found a satisfactory answer.

I have the following composite type:

CREATE TYPE collect.event_record AS (
    event_type      integer
  , event_timestamp timestamp without time zone
  , event_data      text
  , event_import_id integer
  );

I have the following function:

CREATE OR REPLACE FUNCTION collect.insert_events(
    fail_on_duplicates boolean,
    source_public_id text,
    event_records collect.event_record[])
  RETURNS integer AS
  ...

On the postgres side everything seems to work fine. Now I just need to invoke it from java/kotlin.

We use this version of postgres driver:

compile group: "org.postgresql", name: "postgresql", version: "9.4.1212"

On PreparedStatement there's a method that seems to be what I am looking for:

void setArray (int parameterIndex, Array x) throws SQLException;

The array type is java.sql.Array which from what I can tell can be created using the Connection object:

Array createArrayOf(String typeName, Object[] elements) throws SQLException;

However, here I am not sure what to put in. What should typeName be? I imagine that I should create a class that matches the composite type and that I serialize the fields as necessary or it's an array of java.sql.Struct .

I have been googling for examples but they seem to deal with primitive types mostly which doesn't help in my case.

An alternative is to refactor insert_events to accept several arrays of primitive types, sort of a column view of my objects.

Another alternative is to send in a JSON array which I transform into an array of collect.event_record[] inside the postgres function.

However, I would like to find a way that allowed me to keep the postgres function signature I have currently.

Any ideas are greatly appreciated.

Answer 1

As far as I know the Postgres jdbc driver doesn't support Struct, but there is another workaround for arrays of composite types. The documentation says that it is possible to create an instance of a composite type using the following construction: (value_of_event_type,value_of_event_timestamp,value_of_event_data,value_event_import_id) . The event_record data structure can be defined in the following way:

data class EventRecord(
    val eventType: Int,
    val eventTimestamp: Instant,
    val eventData: String,
    val eventImportId: Int) {

    fun toSqlRow(): String {
        return ("(" + eventType + ","
                    + eventTimestamp + ","
                    + eventData + ","
                    + eventImportId +
                ")")
    }
}

The next step is to create PreparedStatement :

val preparedStatement = con.prepareStatement("SELECT * FROM public.insert_events(?, ?, ?)")
// ... define other parameters
preparedStatement.setArray(3, con.createArrayOf("public.event_record", records.map { e -> e.toSqlRow() }.toTypedArray()))

Created PreparedStatement can be used to query the database.

PS: The current implementation will not work for text values containing , , " , ' . Wrap the text value in quotes if it contains , and replace " with \\" .