Add DB trigger to populate SIGMA DAO table (#678)

Author: rmeena840

examples/dao/README.md

@@ -68,6 +68,12 @@ We use functional notation to describe use cases we will implement.
 - `withdraw_from_proposal()` - Withdraw the assets from the proposalLsig back to the owner. Receiver must be the owner of the proposalLsig. Transaction composition:
  - _tx0_: Withdraw _gov_tokens_ from _proposalLsig_ back to _proposer_ (owner) (ASA transfer).
 
+## Setup Sigma Dao
+
+Setup the sigma_daos table. Indexer should be running before executing below script.
+
+    psql -U algorand -d pgdb -a -f setup_sigma_dao.sql
+
 ## Spec document
 
 Algo Builder DAO [specification](https://paper.dropbox.com/doc/Algo-Builder-DAO--BRlh~FwufNzIzk4wNUuAjLTuAg-ncLdytuFa7EJrRerIASSl).

examples/dao/setup_sigma_dao.sql

@@ -0,0 +1,48 @@
+-- #Note: Indexer should be running before executing the queries present in this file
+-- Indexer schema:
+--  https://github.com/algorand/indexer/blob/develop/idb/postgres/internal/schema/setup_postgres.sql
+
+-- create a sigma_daos table if does not exit already.
+CREATE TABLE IF NOT EXISTS sigma_daos (
+  app_id bigint PRIMARY KEY, -- application id
+  app_params jsonb, -- application params with approval etc.
+  asset_id bigint -- token id
+);
+
+-- create a procedure to handle the trigger (sigmadao_trigger_fn) action
+CREATE OR REPLACE FUNCTION sigmadao_trigger_fn()
+RETURNS TRIGGER
+AS $$
+DECLARE
+    asset_id bigint;
+	log_sigma text := 'U2lnbWFEQU8gY3JlYXRlZA==';
+	i record;
+BEGIN
+	/* 	txn colmun of txn relation stores both asset and app id. typeenum column
+		identifies the asset and app */
+	FOR i IN SELECT txn FROM txn WHERE asset = NEW.asset AND typeenum=6 LOOP
+		/*	sigma dao contrac check. Here 'dt' and 'lg' is a json object present
+			in each record of txn column */
+		IF i.txn::jsonb -> 'dt'->'lg' ?& ARRAY[log_sigma] THEN
+			-- TODO: Fetch asset id from global state not from latest entry in asset table
+			-- store token id from db to above decalred variable asset_id
+			SELECT index INTO asset_id FROM public.asset ORDER BY index DESC LIMIT 1;
+			-- insert values in sigma_daos table
+			INSERT INTO public.sigma_daos (
+			app_id, app_params, asset_id)
+			VALUES (NEW.asset, NEW.txn, asset_id);
+			EXIT;
+		END IF;
+    END LOOP;
+	RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- create a trigger (sigmadao_trigger)
+-- Event: INSERT on publoc.txn relation
+CREATE TRIGGER sigmadao_trigger
+AFTER INSERT ON public.txn FOR EACH ROW
+EXECUTE FUNCTION sigmadao_trigger_fn();
+
+-- grant privileges to relation sigma_daos
+GRANT ALL PRIVILEGES ON TABLE sigma_daos TO algorand;