From 972ebcc2a672c3519a10f34228fe5cab71f8f334 Mon Sep 17 00:00:00 2001
From: Mihitoko <max-lotz@outlook.de>
Date: Sat, 4 Nov 2023 00:58:35 +0100
Subject: [PATCH] Fix #3786 collations not dropped on clean

---
 .../database/postgresql/PostgreSQLSchema.java | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/flyway-database/flyway-database-postgresql/src/main/java/org/flywaydb/database/postgresql/PostgreSQLSchema.java b/flyway-database/flyway-database-postgresql/src/main/java/org/flywaydb/database/postgresql/PostgreSQLSchema.java
index 9f8f553e9..c6521f3ef 100644
--- a/flyway-database/flyway-database-postgresql/src/main/java/org/flywaydb/database/postgresql/PostgreSQLSchema.java
+++ b/flyway-database/flyway-database-postgresql/src/main/java/org/flywaydb/database/postgresql/PostgreSQLSchema.java
@@ -117,6 +117,10 @@ protected void doClean() throws SQLException {
             jdbcTemplate.execute(statement);
         }
 
+        for (String statement : generateDropStatementsForCollations()) {
+            jdbcTemplate.execute(statement);
+        }
+
         for (String statement : generateDropStatementsForExtensions()) {
             jdbcTemplate.execute(statement);
         }
@@ -340,6 +344,31 @@ private List<String> generateDropStatementsForViews() throws SQLException {
         return statements;
     }
 
+    /**
+     * Generates the statements for dropping the collations in this schema.
+     *
+     * @return The drop statements.
+     * @throws SQLException when the clean statements could not be generated.
+     */
+    private List<String> generateDropStatementsForCollations() throws SQLException {
+        List<String> collationNames =
+                jdbcTemplate.queryForStringList(
+                        // Search for all collations in current schema
+                        "SELECT c.collname FROM pg_catalog.pg_collation c " +
+                                // that don't depend on an extension
+                                "JOIN pg_namespace n ON c.collnamespace = n.oid " +
+                                "LEFT JOIN pg_depend dep ON dep.objid = c.oid AND dep.deptype = 'e' " +
+                                "WHERE n.nspname = ? AND dep.objid IS NULL",
+                        name);
+
+        List<String> statements = new ArrayList<>();
+        for (String collationName : collationNames) {
+            statements.add("DROP COLLATION IF EXISTS " + database.quote(name, collationName) + " CASCADE");
+        }
+
+        return statements;
+    }
+
     @Override
     protected PostgreSQLTable[] doAllTables() throws SQLException {
         List<String> tableNames =