[core] Fix the caching catalog to properly handle case sensitivity fo…

…r system table

paimon-core/src/main/java/org/apache/paimon/catalog/Identifier.java

@@ -58,6 +58,7 @@ public class Identifier implements Serializable {
 
     private transient String table;
     private transient String branch;
+    // SystemTable name is case-insensitive and will consistently be returned in lowercase.
     private transient String systemTable;
 
     public Identifier(String database, String object) {
@@ -116,7 +117,7 @@ public String getBranchNameOrDefault() {
 
     public @Nullable String getSystemTableName() {
         splitObjectName();
-        return systemTable;
+        return systemTable == null ? null : systemTable.toLowerCase();
     }
 
     private void splitObjectName() {
@@ -187,12 +188,15 @@ public boolean equals(Object o) {
             return false;
         }
         Identifier that = (Identifier) o;
-        return Objects.equals(database, that.database) && Objects.equals(object, that.object);
+        return Objects.equals(database, that.database)
+                && Objects.equals(getTableName(), that.getTableName())
+                && Objects.equals(getBranchName(), that.getBranchName())
+                && Objects.equals(getSystemTableName(), that.getSystemTableName());
     }
 
     @Override
     public int hashCode() {
-        return Objects.hash(database, object);
+        return Objects.hash(database, getTableName(), getBranchName(), getSystemTableName());
     }
 
     @Override

paimon-core/src/test/java/org/apache/paimon/catalog/CachingCatalogTest.java

@@ -106,9 +106,14 @@ public void testInvalidateSysTablesIfBaseTableIsDropped() throws Exception {
         catalog.createTable(new Identifier("db", "tbl"), DEFAULT_TABLE_SCHEMA, false);
         Identifier sysIdent = new Identifier("db", "tbl$files");
         catalog.getTable(sysIdent);
+        Identifier sysIdent1 = new Identifier("db", "tbl$SNAPSHOTS");
+        catalog.getTable(sysIdent1);
+
         catalog.dropTable(tableIdent, false);
         assertThatThrownBy(() -> catalog.getTable(sysIdent))
                 .hasMessage("Table db.tbl does not exist.");
+        assertThatThrownBy(() -> catalog.getTable(sysIdent1))
+                .hasMessage("Table db.tbl does not exist.");
     }
 
     @Test

paimon-core/src/test/java/org/apache/paimon/catalog/IdentifierTest.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.paimon.catalog;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/** Test for {@link Identifier}. */
+public class IdentifierTest {
+
+    @Test
+    public void testIdentifierEquals() {
+        assertThat(new Identifier("db", "tbl")).isNotEqualTo(new Identifier("DB", "tbl"));
+        assertThat(new Identifier("db", "tbl")).isNotEqualTo(new Identifier("db", "TBL"));
+        assertThat(new Identifier("db", "tbl$branch_test"))
+                .isNotEqualTo(new Identifier("db", "tbl$branch_TEST"));
+        assertThat(new Identifier("db", "tbl$files")).isEqualTo(new Identifier("db", "tbl$FILES"));
+        assertThat(new Identifier("db", "tbl$branch_test$files"))
+                .isEqualTo(new Identifier("db", "tbl$branch_test$FILES"));
+    }
+}

paimon-spark/paimon-spark-ut/src/test/scala/org/apache/paimon/spark/PaimonSparkTestBase.scala

@@ -66,7 +66,6 @@ class PaimonSparkTestBase
     super.sparkConf
       .set("spark.sql.catalog.paimon", classOf[SparkCatalog].getName)
       .set("spark.sql.catalog.paimon.warehouse", tempDBDir.getCanonicalPath)
-      .set("spark.sql.catalog.paimon.cache-enabled", "false")
       .set("spark.sql.extensions", classOf[PaimonSparkSessionExtensions].getName)
       .set("spark.serializer", serializer)
   }