fix(jdbc): DatabaseMetaData#getPrimaryKeys and getExportedKeys should…

… return an empty ResultSet for sqlite_schema

those 2 functions rely on querying sqlite_schema for information, which doesn't contain information about itself.
sqlite_schema doesn't have any imported/exported/primary key, so returning an empty ResultSet is better than throwing an exception

Closes: #831

src/main/java/org/sqlite/jdbc3/JDBC3DatabaseMetaData.java

@@ -1979,6 +1979,11 @@ class PrimaryKeyFinder {
         public PrimaryKeyFinder(String table) throws SQLException {
             this.table = table;
 
+            // specific handling for sqlite_schema and synonyms, so that
+            // getExportedKeys/getPrimaryKeys return an empty ResultSet instead of throwing an
+            // exception
+            if ("sqlite_schema".equals(table) || "sqlite_master".equals(table)) return;
+
             if (table == null || table.trim().length() == 0) {
                 throw new SQLException("Invalid table name: '" + this.table + "'");
             }

src/test/java/org/sqlite/DBMetaDataTest.java

@@ -18,8 +18,11 @@
 import java.util.Properties;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.DisabledInNativeImage;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 /** These tests are designed to stress Statements on memory databases. */
 public class DBMetaDataTest {
@@ -1596,4 +1599,31 @@ public void version() throws Exception {
         assertThat(meta.getDatabaseMinorVersion()).as("db minor version").isEqualTo(minorVersion);
         assertThat(meta.getUserName()).as("user name").isNull();
     }
+
+    @Nested
+    class SqliteSchema {
+        @ParameterizedTest
+        @ValueSource(strings = {"sqlite_schema", "sqlite_master"})
+        public void getImportedKeys(String table) throws SQLException {
+            ResultSet importedKeys = meta.getImportedKeys(null, null, table);
+
+            assertThat(importedKeys.next()).isFalse();
+        }
+
+        @ParameterizedTest
+        @ValueSource(strings = {"sqlite_schema", "sqlite_master"})
+        public void getExportedKeys(String table) throws SQLException {
+            ResultSet exportedKeys = meta.getExportedKeys(null, null, table);
+
+            assertThat(exportedKeys.next()).isFalse();
+        }
+
+        @ParameterizedTest
+        @ValueSource(strings = {"sqlite_schema", "sqlite_master"})
+        public void getPrimaryKeys(String table) throws SQLException {
+            ResultSet primaryKeys = meta.getPrimaryKeys(null, null, table);
+
+            assertThat(primaryKeys.next()).isFalse();
+        }
+    }
 }