From fe43d0b1d04b99f25a78ecd093d480e632e2207d Mon Sep 17 00:00:00 2001
From: shaharuk-yb <sshaikh@yugabyte.com>
Date: Tue, 23 Jul 2024 18:12:32 +0530
Subject: [PATCH] perf-data-loader: suggested order of data loading into tables

---
 .../dataloader/DataGeneratorLoader.java       | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/src/main/java/com/oltpbenchmark/benchmarks/dataloader/DataGeneratorLoader.java b/src/main/java/com/oltpbenchmark/benchmarks/dataloader/DataGeneratorLoader.java
index ee964971d..9f476f1c0 100644
--- a/src/main/java/com/oltpbenchmark/benchmarks/dataloader/DataGeneratorLoader.java
+++ b/src/main/java/com/oltpbenchmark/benchmarks/dataloader/DataGeneratorLoader.java
@@ -560,10 +560,41 @@ public void getDistinctValuesFromParentTable(Connection conn, List<ForeignKey> f
                 while (rs.next()) {
                     distinctValues.add(rs.getObject(1));
                 }
+                if (distinctValues.isEmpty()) {
+                    List<String> hierarchy = getParentTableHierarchy(foreignKey.getForeignTableName(), conn);
+
+                    StringBuilder loadOrder = new StringBuilder(String.format("There are no entries in the parent " +
+                            "table `%s` for column `%s` to be used as foreign key. Consider loading tables in " +
+                            "following order: ", foreignKey.getForeignTableName(),
+                        foreignKey.getForeignColumnName()));
+                    for (String table: hierarchy) {
+                        loadOrder.append(table).append(" --> ");
+                    }
+                    loadOrder.append(foreignKey.getTableName());
+                    throw new RuntimeException(loadOrder.toString());
+                }
                 foreignKey.setDistinctValues(distinctValues);
             } catch (SQLException e) {
                 e.printStackTrace();
             }
         }
     }
+    public static List<String> getParentTableHierarchy(String tableName, Connection conn) {
+        List<String> tableHierarchy = new ArrayList<>();
+        findParentTables(tableName, conn, tableHierarchy);
+        return tableHierarchy;
+    }
+
+    private static void findParentTables(String tableName, Connection conn, List<String> tableHierarchy) {
+        List<ForeignKey> foreignKeys = getForeignKeys(tableName, conn);
+
+        if (foreignKeys.isEmpty()) {
+            tableHierarchy.add(tableName);
+        } else {
+            for (ForeignKey foreignKey : foreignKeys) {
+                findParentTables(foreignKey.getForeignTableName(), conn, tableHierarchy);
+            }
+            tableHierarchy.add(tableName);
+        }
+    }
 }