Merge pull request #53 from yugabyte/gh_23327

[YugabyteDB plugin] Use single connection for both schema history table management and applying migrations

Author: piers-williams

flyway-database-yugabytedb/src/main/java/org/flywaydb/community/database/postgresql/yugabytedb/YugabyteDBDatabase.java

@@ -77,18 +77,9 @@ public String getRawCreateScript(Table table, boolean baseline) {
                 "CREATE INDEX IF NOT EXISTS \"" + table.getName() + "_s_idx\" ON " + table + " (\"success\");";
     }
 
-    /**
-     * YugabyteDB does not support PG Advisor Locks. So the YugabyteDB plugin
-     * employs SELECT ... FOR UPDATE in a transaction to implement locking for
-     * Flyway operations instead of the PG Advisory locks. If a single
-     * connection is used, it may cause issues if multiple threads execute
-     * begin/commit on it for Flyway operations. Returning false from this
-     * method ensures the same connection is not used for migrations.
-     * @return false
-     */
     @Override
     public boolean useSingleConnection() {
-        return false;
+        return true;
     }
 
     private void createLockTable() {

flyway-database-yugabytedb/src/main/java/org/flywaydb/community/database/postgresql/yugabytedb/YugabyteDBExecutionTemplate.java

@@ -8,16 +8,16 @@
 import org.flywaydb.core.internal.util.FlywayDbWebsiteLinks;
 
 import java.sql.*;
-import java.util.HashMap;
+import java.util.Map;
 import java.util.concurrent.Callable;
+import java.util.concurrent.ConcurrentHashMap;
 
 @CustomLog
 public class YugabyteDBExecutionTemplate {
 
     private final JdbcTemplate jdbcTemplate;
     private final String tableName;
-    private final HashMap<String, Boolean> tableEntries = new HashMap<>();
-
+    private static final Map<String, Boolean> tableEntries = new ConcurrentHashMap<>();
 
     YugabyteDBExecutionTemplate(JdbcTemplate jdbcTemplate, String tableName) {
         this.jdbcTemplate = jdbcTemplate;