text: CREATE TYPE operation_type AS ENUM ('deposit', 'withdrawal');
  
  CREATE TABLE "operations"
  (
      "id"           bigserial PRIMARY KEY,
      "wallet"       varchar        NOT NULL DEFAULT 'system',
      "type"         operation_type NOT NULL,
      "amount"       bigint         NOT NULL DEFAULT 0,
      "other_wallet" varchar        NOT NULL DEFAULT 'system',
      "created_at"   timestamptz    NOT NULL DEFAULT now()
  );
  
  CREATE INDEX ON "operations" ("wallet", "type", "created_at");
  
  /*
  INSERT INTO operations (wallet, type, amount)
  VALUES ('wallet01', 'deposit', 100000),
         ('wallet02', 'deposit', 100000);
  */
  