modify status and error db constraints

apps/explorer/priv/repo/migrations/20190122125815_change_transaction_error_constraint.exs

@@ -0,0 +1,85 @@
+defmodule Explorer.Repo.Migrations.ChangeTransactionErrorConstraint do
+  use Ecto.Migration
+
+  def change do
+    drop(
+      constraint(
+        :transactions,
+        :status
+      ))
+
+    create(
+      constraint(
+        :transactions,
+        :status,
+        # 0 - NULL
+        # 1 - NOT NULL
+        #
+        # | block_hash | internal_transactions_indexed_at | status | OK | description
+        # |------------|----------------------------------|--------|----|------------
+        # | 0          | 0                                | 0      | 1  | pending
+        # | 0          | 0                                | 1      | 0  | pending with status
+        # | 0          | 1                                | 0      | 0  | pending with internal transactions
+        # | 0          | 1                                | 1      | 0  | pending with internal transactions and status
+        # | 1          | 0                                | 0      | 1  | pre-byzantium collated transaction without internal transactions
+        # | 1          | 0                                | 1      | 1  | post-byzantium collated transaction without internal transactions
+        # | 1          | 1                                | 0      | 0  | pre-byzantium collated transaction with internal transaction without status
+        # | 1          | 1                                | 1      | 1  | pre- or post-byzantium collated transaction with internal transactions and status
+        #
+        # [Karnaugh map](https://en.wikipedia.org/wiki/Karnaugh_map)
+        # b \ is | 00 | 01 | 11 | 10 |
+        # -------|----|----|----|----|
+        #      0 | 1  | 0  | 0  | 0  |
+        #      1 | 1  | 1  | 1  | 0  |
+        #
+        # Simplification: ¬i·¬s + b·¬i + b·s
+        check: """
+        (internal_transactions_indexed_at IS NULL AND status IS NULL) OR
+        (block_hash IS NOT NULL AND internal_transactions_indexed_at IS NULL) OR
+        (block_hash IS NOT NULL AND status IS NOT NULL) OR
+        (status = 0 and error = 'dropped/replaced')
+        """
+      ))
+
+    drop(
+      constraint(
+        :transactions,
+        :error
+      ))
+
+    create(
+      constraint(
+        :transactions,
+        :error,
+        # | status | internal_transactions_indexed_at | error    | OK         | description
+        # |--------|----------------------------------|----------|------------|------------
+        # | NULL   | NULL                             | NULL     | TRUE       | pending or pre-byzantium collated
+        # | NULL   | NULL                             | NOT NULL | FALSE      | error cannot be known before internal transactions are indexed
+        # | NULL   | NOT NULL                         | NULL     | DON'T CARE | handled by `status` check
+        # | NULL   | NOT NULL                         | NOT NULL | FALSE      | error cannot be set unless status is known to be error (`0`)
+        # | 0      | NULL                             | NULL     | TRUE       | post-byzantium before internal transactions indexed
+        # | 0      | NULL                             | NOT NULL | FALSE      | error cannot be set unless internal transactions are indexed
+        # | 0      | NOT NULL                         | NULL     | FALSE      | error MUST be set when status is error
+        # | 0      | NOT NULL                         | NOT NULL | TRUE       | error is set when status is error
+        # | 1      | NULL                             | NULL     | TRUE       | post-byzantium before internal transactions indexed
+        # | 1      | NULL                             | NOT NULL | FALSE      | error cannot be set when status is ok
+        # | 1      | NOT NULL                         | NULL     | TRUE       | error is not set when status is ok
+        # | 1      | NOT NULL                         | NOT NULL | FALSE      | error cannot be set when status is ok
+        #
+        # Karnaugh map
+        # s \ ie | NULL, NULL | NULL, NOT NULL | NOT NULL, NOT NULL | NOT NULL, NULL |
+        # -------|------------|----------------|--------------------|----------------|
+        # NULL   | TRUE       | FALSE          | FALSE              | DON'T CARE     |
+        # 0      | TRUE       | FALSE          | TRUE               | FALSE          |
+        # 1      | TRUE       | FALSE          | FALSE              | TRUE           |
+        #
+        check: """
+        (internal_transactions_indexed_at IS NULL AND error IS NULL) OR
+        (status = 0 AND internal_transactions_indexed_at IS NOT NULL AND error IS NOT NULL) OR
+        (status != 0 AND internal_transactions_indexed_at IS NOT NULL AND error IS NULL) OR
+        (status = 0 and error = 'dropped/replaced')
+        """
+      )
+    )
+  end
+end