Audit trigger (Statement Level) storing identifier of inserted/updated/deleted rows - postgresql

Question

I have the following small MVWE for a basic micro-auditing system which works fine but lacks a functionality:
DROP TABLE IF EXISTS audit CASCADE;
CREATE TABLE audit(
Id BIGSERIAL NOT NULL
,TimeValue TIMESTAMP NOT NULL
,RoleName NAME NOT NULL
,Operation NAME NOT NULL
,SchemaName NAME NOT NULL
,TableName NAME NOT NULL
,Identifiers BIGINT[]
---
,PRIMARY KEY(Id)
);
-- Audit Trigger:
DROP FUNCTION IF EXISTS audit_trigger() CASCADE;
CREATE OR REPLACE FUNCTION audit_trigger()
RETURNS TRIGGER AS
$BODY$
BEGIN
INSERT INTO audit(TimeValue, RoleName, Operation, SchemaName, TableName) VALUES
(now()::TIMESTAMP, current_user, TG_OP, TG_TABLE_SCHEMA, TG_RELNAME);
RETURN NULL;
END;
$BODY$
LANGUAGE plpgsql SECURITY DEFINER;
-- Channels:
DROP TABLE IF EXISTS channels CASCADE;
CREATE TABLE channels(
Id INTEGER NOT NULL
,UserKey TEXT NOT NULL
,Active BOOLEAN NOT NULL DEFAULT(TRUE)
---
,PRIMARY KEY(Id)
,UNIQUE(UserKey)
);
CREATE TRIGGER channel_audit_trigger BEFORE INSERT OR UPDATE OR DELETE ON channels
FOR EACH STATEMENT EXECUTE PROCEDURE audit_trigger();
-- Perform some operations:
INSERT INTO channels(
SELECT C.Id, 'Channel-' || C.Id
FROM generate_series(1, 300, 10) AS C(Id)
);
DELETE FROM channels WHERE id < 10;
UPDATE channels
SET UserKey = 'wild channel'
WHERE id = 21;
I would like to add into the last column of audit table, identifiers of rows that have been inserted/updated/deleted in channels.
I have used STATEMENT level because I just need to collects identifiers in a array. But I do not find how to access DML statistics. Conversely at the ROW level I must handle OLD and NEW cases and I cannot succeed in aggregate all touched identifier.
How can I proceed in order to fill the last column of audit table with touched identifiers?
Update
Finally I reached my goal, but this solution might not be scalable and may have some unwanted drawbacks (I am open to any constructive feedback and advice).
Basically, how I have solved my problem:
Log at ROW level BEFORE DML is performed into a table audit_rowlevel;
Aggregate the freshly added content of audit_rowlevel into audit_statementlevel at STATEMENT level AFTER DML is performed;
Minimal Working Example is now:
DROP TABLE IF EXISTS audit_rowlevel CASCADE;
CREATE TABLE audit_rowlevel(
Id BIGSERIAL NOT NULL
,Aggregated BOOLEAN NOT NULL DEFAULT(FALSE)
,TimeValue TIMESTAMP NOT NULL
-- https://www.postgresql.org/docs/current/static/functions-info.html
,RoleName NAME NOT NULL
,ClientIP INET NOT NULL
,ClientPid INTEGER NOT NULL
-- https://www.postgresql.org/docs/current/static/plpgsql-trigger.html
,Operation TEXT NOT NULL
,SchemaName NAME NOT NULL
,TableName NAME NOT NULL
,RowId BIGINT NOT NULL
-- https://www.postgresql.org/docs/current/static/functions-json.html
,OldValue JSONB
,NewValue JSONB
---
,PRIMARY KEY(Id)
);
-- Row Level Trigger:
DROP FUNCTION IF EXISTS audit_rowlevel_trigger() CASCADE;
CREATE OR REPLACE FUNCTION audit_rowlevel_trigger()
RETURNS TRIGGER AS
$BODY$
DECLARE
history BOOLEAN := (TG_NARGS > 0) AND (TG_ARGV[0]::BOOLEAN);
rowid BIGINT;
oldvalue JSONB;
newvalue JSONB;
BEGIN
-- Handle NEW:
IF TG_OP = ANY('{INSERT,UPDATE}') THEN
IF history THEN
newvalue := to_jsonb(NEW);
END IF;
rowid := NEW.Id::BIGINT;
END IF;
-- Handle OLD:
IF TG_OP = ANY('{UPDATE,DELETE}') THEN
IF history THEN
oldvalue := to_jsonb(OLD);
END IF;
rowid := OLD.Id::BIGINT;
END IF;
-- INSERT:
INSERT INTO audit_rowlevel(TimeValue, RoleName, ClientIP, ClientPID, Operation, SchemaName, TableName, RowId, NewValue, OldValue) VALUES
(now()::TIMESTAMP, current_user, inet_client_addr(), pg_backend_pid(), TG_OP, TG_TABLE_SCHEMA, TG_RELNAME, RowId, NewValue, OldValue);
-- RETURN:
IF TG_OP = ANY('{INSERT,UPDATE}') THEN
RETURN NEW;
ELSIF TG_OP = 'DELETE' THEN
RETURN OLD;
ELSE
RETURN NULL;
END IF;
END;
$BODY$
LANGUAGE plpgsql SECURITY DEFINER;
-- Statement Level Trigger:
DROP TABLE IF EXISTS audit_statementlevel CASCADE;
CREATE TABLE audit_statementlevel(
Id BIGSERIAL NOT NULL
,TimeValue TIMESTAMP NOT NULL
,RoleName NAME NOT NULL
,ClientIP INET NOT NULL
,ClientPid INTEGER NOT NULL
,Operation TEXT NOT NULL
,SchemaName NAME NOT NULL
,TableName NAME NOT NULL
,RowCount BIGINT NOT NULL
,RowIds BIGINT[] NOT NULL
,AuditIds BIGINT[] NOT NULL
---
,PRIMARY KEY(Id)
);
-- Row Level Trigger:
DROP FUNCTION IF EXISTS audit_statementlevel_trigger() CASCADE;
CREATE OR REPLACE FUNCTION audit_statementlevel_trigger()
RETURNS TRIGGER AS
$BODY$
DECLARE
rowcount BIGINT;
BEGIN
WITH
A AS (
SELECT
TimeValue, RoleName, ClientIP, ClientPid, Operation, SchemaName, TableName
,COUNT(*)
,array_agg(RowId)
,array_agg(Id)
FROM
audit_rowlevel
WHERE
NOT Aggregated
GROUP BY
TimeValue, RoleName, ClientIP, ClientPid, Operation, SchemaName, TableName
ORDER BY
TimeValue
),
B AS (
INSERT INTO audit_statementlevel(TimeValue, RoleName, ClientIP, ClientPid, Operation, SchemaName, TableName, RowCount, RowIds, AuditIds)
(SELECT * FROM A)
RETURNING AuditIds
),
C AS (
SELECT array_agg(DISTINCT T.id) AS Ids FROM B, unnest(B.AuditIds) AS T(id)
)
UPDATE
audit_rowlevel
SET
Aggregated = TRUE
FROM
C
WHERE
Id = ANY(C.Ids);
RETURN NULL;
END;
$BODY$
LANGUAGE plpgsql SECURITY DEFINER;
-- Channels:
DROP TABLE IF EXISTS channels CASCADE;
CREATE TABLE channels(
Id INTEGER NOT NULL
,UserKey TEXT NOT NULL
,Active BOOLEAN NOT NULL DEFAULT(TRUE)
---
,PRIMARY KEY(Id)
,UNIQUE(UserKey)
);
CREATE TRIGGER channel_audit_rowlevel_trigger BEFORE INSERT OR UPDATE OR DELETE ON channels
FOR EACH ROW EXECUTE PROCEDURE audit_rowlevel_trigger(TRUE);
CREATE TRIGGER channel_audit_statementlevel_trigger AFTER INSERT OR UPDATE OR DELETE ON channels
FOR EACH STATEMENT EXECUTE PROCEDURE audit_statementlevel_trigger();
-- Perform some operations:
INSERT INTO channels(
SELECT C.Id, 'Channel-' || C.Id
FROM generate_series(1, 300, 10) AS C(Id)
);
DELETE FROM channels WHERE id < 10;
UPDATE channels
SET UserKey = 'wild channel'
WHERE id = 21;
I am interested knowing if this solution looks right to professional developers.
Am I going into the good direction or is this solution evil?