Add migration to calculate the account statistics for the past

financer-server/src/main/java/database/common/V22_0_1__calculateAccountStatistics.java

@@ -0,0 +1,111 @@
+package database.common;
+
+import org.flywaydb.core.api.migration.BaseJavaMigration;
+import org.flywaydb.core.api.migration.Context;
+
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+public class V22_0_1__calculateAccountStatistics extends BaseJavaMigration {
+    private static class TransactionPeriodAccountsContainer {
+        public Long transactionAmount;
+        public Long expensePeriodId;
+        public Long fromAccountId;
+        public Long toAccountId;
+
+        public TransactionPeriodAccountsContainer(Long transactionAmount, Long expensePeriodId, Long fromAccountId, Long toAccountId) {
+            this.transactionAmount = transactionAmount;
+            this.expensePeriodId = expensePeriodId;
+            this.fromAccountId = fromAccountId;
+            this.toAccountId = toAccountId;
+        }
+    }
+
+    private static final String GET_CONTAINERS_SQL = "SELECT t.amount, p.id, t.from_account_id, t.to_account_id FROM \"transaction\" t INNER JOIN link_transaction_period ltp ON ltp.transaction_id = t.id INNER JOIN period p ON p.id = ltp.period_id WHERE p.type = 'EXPENSE'";
+
+    private static final String ACCOUNT_STATISTIC_EXISTS_SQL = "SELECT id FROM account_statistic WHERE account_id = ? AND period_id = ?";
+
+    private static final String ACCOUNT_STATISTIC_UPDATE_FROM_SQL = "UPDATE account_statistic SET spending_total_from = spending_total_from + ?, transaction_count_from = transaction_count_from + 1 WHERE id = ?";
+
+    private static final String ACCOUNT_STATISTIC_UPDATE_TO_SQL = "UPDATE account_statistic SET spending_total_to = spending_total_to + ?, transaction_count_to = transaction_count_to + 1 WHERE id = ?";
+
+    private static final String ACCOUNT_STATISTIC_INSERT_FROM_SQL = "INSERT INTO account_statistic(account_id, period_id, spending_total_from, transaction_count_from, spending_total_to, transaction_count_to) VALUES(?, ?, ?, 1, 0, 0)";
+
+    private static final String ACCOUNT_STATISTIC_INSERT_TO_SQL = "INSERT INTO account_statistic(account_id, period_id, spending_total_from, transaction_count_from, spending_total_to, transaction_count_to) VALUES(?, ?, 0, 0, ?, 1)";
+
+    @Override
+    public void migrate(Context context) throws Exception {
+        final List<TransactionPeriodAccountsContainer> cons = getContainers(context);
+
+        for (TransactionPeriodAccountsContainer con : cons) {
+            handleAccount(con, context, true);
+            handleAccount(con, context, false);
+        }
+    }
+
+    private void handleAccount(TransactionPeriodAccountsContainer con, Context context, boolean from) throws SQLException {
+        try (PreparedStatement statement =
+                     context
+                             .getConnection()
+                             .prepareStatement(ACCOUNT_STATISTIC_EXISTS_SQL)) {
+            statement.setLong(1, from ? con.fromAccountId : con.toAccountId);
+            statement.setLong(2, con.expensePeriodId);
+
+            final ResultSet rs = statement.executeQuery();
+            boolean found = false;
+
+            // Only one possible entry because of the unique constraint
+            while(rs.next()) {
+                found = true;
+
+                try (PreparedStatement statementUpdate =
+                             context
+                                     .getConnection()
+                                     .prepareStatement(from ? ACCOUNT_STATISTIC_UPDATE_FROM_SQL : ACCOUNT_STATISTIC_UPDATE_TO_SQL)) {
+                    statementUpdate.setLong(1, con.transactionAmount);
+                    statementUpdate.setLong(2, rs.getLong(1));
+
+                    statementUpdate.executeUpdate();
+                }
+            }
+
+            // We need to create a new account_statistic entry for the tuple {account_id;report_id}
+            if (!found) {
+                try (PreparedStatement statementInsert =
+                             context
+                                     .getConnection()
+                                     .prepareStatement(from ? ACCOUNT_STATISTIC_INSERT_FROM_SQL : ACCOUNT_STATISTIC_INSERT_TO_SQL)) {
+                    statementInsert.setLong(1, from ? con.fromAccountId : con.toAccountId);
+                    statementInsert.setLong(2, con.expensePeriodId);
+                    statementInsert.setLong(3, con.transactionAmount);
+
+                    statementInsert.execute();
+                }
+            }
+        }
+    }
+
+    private List<TransactionPeriodAccountsContainer> getContainers(Context context) throws SQLException {
+        try (PreparedStatement statement =
+                 context
+                     .getConnection()
+                     .prepareStatement(GET_CONTAINERS_SQL)) {
+            final ResultSet rs = statement.executeQuery();
+            final List<TransactionPeriodAccountsContainer> cons = new ArrayList<>();
+
+            while(rs.next()) {
+                cons.add(new TransactionPeriodAccountsContainer(
+                        rs.getLong(1), // transaction amount
+                        rs.getLong(2), // expense period ID
+                        rs.getLong(3), // from account ID
+                        rs.getLong(4)  // to account ID
+                ));
+            }
+
+            return cons;
+        }
+    }
+}

financer-server/src/main/java/database/package-info.java

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+/**
+ * Package for Java based database migrations via Flyway
+ */
+package database;

financer-server/src/main/resources/database/common/V22_0_0__accountStatisticUniqueConstraint.sql

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+ALTER TABLE account_statistic
+ADD CONSTRAINT un_account_statistic_account_period UNIQUE (account_id,period_id);