fix psotgresql init failed due to not exist same name db with user

hugegraph-dist/src/assembly/static/conf/hugegraph.properties

@@ -77,6 +77,7 @@ cassandra.password=
 #jdbc.url=jdbc:postgresql://localhost:5432/
 #jdbc.username=postgres
 #jdbc.password=
+#jdbc.postgresql.connect_database=template1
 
 # palo backend config
 #palo.host=127.0.0.1

hugegraph-mysql/src/main/java/com/baidu/hugegraph/backend/store/mysql/MysqlSessions.java

@@ -30,6 +30,7 @@
 import java.util.stream.IntStream;
 
 import org.apache.http.client.utils.URIBuilder;
+import org.apache.logging.log4j.util.Strings;
 import org.slf4j.Logger;
 
 import com.baidu.hugegraph.backend.BackendException;
@@ -213,13 +214,7 @@ private Connection open(boolean autoReconnect) throws SQLException {
 
     protected String buildUri(boolean withConnParams, boolean withDB,
                               boolean autoReconnect, Integer timeout) {
-        String url = this.config.get(MysqlOptions.JDBC_URL);
-        if (!url.endsWith("/")) {
-            url = String.format("%s/", url);
-        }
-        if (withDB) {
-            url = String.format("%s%s", url, this.database());
-        }
+        String url = this.buildUrlPrefix(withDB);
 
         int maxTimes = this.config.get(MysqlOptions.JDBC_RECONNECT_MAX_TIMES);
         int interval = this.config.get(MysqlOptions.JDBC_RECONNECT_INTERVAL);
@@ -241,6 +236,19 @@ protected String buildUri(boolean withConnParams, boolean withDB,
         return builder.toString();
     }
 
+    protected String buildUrlPrefix(boolean withDB) {
+        String url = this.config.get(MysqlOptions.JDBC_URL);
+        if (!url.endsWith("/")) {
+            url = String.format("%s/", url);
+        }
+        String database = withDB ? this.database() : this.connectDatabase();
+        return String.format("%s%s", url, database);
+    }
+
+    protected String connectDatabase() {
+        return Strings.EMPTY;
+    }
+
     protected URIBuilder newConnectionURIBuilder() {
         return new URIBuilder();
     }

hugegraph-postgresql/src/main/java/com/baidu/hugegraph/backend/store/postgresql/PostgresqlOptions.java

@@ -19,7 +19,10 @@
 
 package com.baidu.hugegraph.backend.store.postgresql;
 
+import static com.baidu.hugegraph.config.OptionChecker.disallowEmpty;
+
 import com.baidu.hugegraph.backend.store.mysql.MysqlOptions;
+import com.baidu.hugegraph.config.ConfigOption;
 
 public class PostgresqlOptions extends MysqlOptions {
 
@@ -36,4 +39,13 @@ public static synchronized PostgresqlOptions instance() {
         }
         return instance;
     }
+
+    public static final ConfigOption<String> POSTGRESQL_CONNECT_DATABASE =
+            new ConfigOption<>(
+                    "jdbc.postgresql.connect_database",
+                    "The database used to connect when init store, " +
+                    "drop store or check store exist.",
+                    disallowEmpty(),
+                    "template1"
+            );
 }

hugegraph-postgresql/src/main/java/com/baidu/hugegraph/backend/store/postgresql/PostgresqlSessions.java

@@ -117,6 +117,11 @@ protected URIBuilder newConnectionURIBuilder() {
         return new URIBuilder().addParameter("loggerLevel", "OFF");
     }
 
+    @Override
+    protected String connectDatabase() {
+        return this.config().get(PostgresqlOptions.POSTGRESQL_CONNECT_DATABASE);
+    }
+
     public static String escapeAndWrapString(String value) {
         StringBuilder builder = new StringBuilder(8 + value.length());
         builder.append('\'');