server: Remove the available field from the balances table

Due to a bug, maintaining this field consistent has been tricky,
now the field is dropped and we use an index over a function instead.

server/app/com/xsn/explorer/data/anorm/dao/BalancePostgresDAO.scala

@@ -16,20 +16,18 @@ class BalancePostgresDAO @Inject() (fieldOrderingSQLInterpreter: FieldOrderingSQ
     SQL(
       """
         |INSERT INTO balances
-        |  (address, received, spent, available)
+        |  (address, received, spent)
         |VALUES
-        |  ({address}, {received}, {spent}, {available})
+        |  ({address}, {received}, {spent})
         |ON CONFLICT (address) DO UPDATE
         |  SET received = balances.received + EXCLUDED.received,
-        |      spent = balances.spent + EXCLUDED.spent,
+        |      spent = balances.spent + EXCLUDED.spent
-        |      available = balances.available + EXCLUDED.available
         |RETURNING address, received, spent
       """.stripMargin
     ).on(
       'address -> balance.address.string,
       'received -> balance.received,
       'spent -> balance.spent,
-      'available -> balance.available
     ).as(parseBalance.singleOpt).flatten
   }
 
@@ -41,7 +39,7 @@ class BalancePostgresDAO @Inject() (fieldOrderingSQLInterpreter: FieldOrderingSQ
     val orderBy = fieldOrderingSQLInterpreter.toOrderByClause(ordering)
     SQL(
       s"""
-        |SELECT address, received, spent, available
+        |SELECT address, received, spent
         |FROM balances
         |WHERE address NOT IN (
         |  SELECT address

server/app/com/xsn/explorer/data/anorm/dao/StatisticsPostgresDAO.scala

@@ -12,9 +12,9 @@ class StatisticsPostgresDAO {
     SQL(
       """
         |SELECT
-        |  (SELECT SUM(available) FROM balances) AS total_supply,
+        |  (SELECT SUM(received - spent) FROM balances) AS total_supply,
         |  (
-        |    SELECT SUM(available) FROM balances
+        |    SELECT SUM(received - spent) FROM balances
         |    WHERE address NOT IN (SELECT address FROM hidden_addresses)
         |  ) AS circulating_supply,
         |  (SELECT COUNT(*) FROM transactions) AS transactions,

server/app/com/xsn/explorer/models/fields/BalanceField.scala

@@ -19,5 +19,8 @@ object BalanceField {
     case _ => None
   }
 
-  implicit val columnNameResolver: ColumnNameResolver[BalanceField] = (field) => field.string
+  implicit val columnNameResolver: ColumnNameResolver[BalanceField] = (field) => field match {
+    case Available => s"(${Received.string} - ${Spent.string})"
+    case f => f.string
+  }
 }

server/conf/evolutions/default/5.sql

@@ -0,0 +1,20 @@
+
+# --- !Ups
+
+DROP INDEX balances_available_index;
+
+ALTER TABLE balances
+DROP COLUMN available;
+
+CREATE INDEX balances_available_index ON balances ((received - spent));
+
+
+# --- !Downs
+
+DROP INDEX balances_available_index;
+
+-- in case this down is applied, the table needs to be rebuilt.
+ALTER TABLE balances
+ADD COLUMN available DECIMAL(30, 15) NOT NULL DEFAULT 0;
+
+CREATE INDEX balances_available_index ON balances (available);

server/test/com/xsn/explorer/data/BalancePostgresDataHandlerSpec.scala

@@ -25,21 +25,6 @@ class BalancePostgresDataHandlerSpec extends PostgresDataHandlerSpec {
       result mustEqual Good(balance)
     }
 
-    "set the available amount" in {
-      val address = DataHelper.createAddress("Xbh5pJdBNm8J9PxnEmwVcuQKRmZZ7DkpcF")
-      val balance = Balance(address, received = BigDecimal(10), spent = BigDecimal(5))
-
-      val result = dataHandler.upsert(balance)
-      result mustEqual Good(balance)
-      database.withConnection { implicit conn =>
-        val available = _root_.anorm
-            .SQL(s"SELECT available FROM balances WHERE address = '${address.string}'")
-            .as(_root_.anorm.SqlParser.get[BigDecimal]("available").single)
-
-        available mustEqual balance.available
-      }
-    }
-
     "update an existing balance" in {
       val address = DataHelper.createAddress("XfAATXtkRgCdMTrj2fxHvLsKLLmqAjhEAt")
       val initialBalance = Balance(address, received = BigDecimal(10), spent = BigDecimal(5))