perf(spanner-jdbc): cache JDBC metadata query strings

java-spanner-jdbc/src/main/java/com/google/cloud/spanner/jdbc/JdbcDatabaseMetaData.java

@@ -20,16 +20,20 @@
 import com.google.auth.ServiceAccountSigner;
 import com.google.auth.oauth2.UserCredentials;
 import com.google.cloud.spanner.Dialect;
+import com.google.cloud.spanner.ErrorCode;
 import com.google.cloud.spanner.ResultSets;
+import com.google.cloud.spanner.SpannerException;
+import com.google.cloud.spanner.SpannerExceptionFactory;
 import com.google.cloud.spanner.Struct;
 import com.google.cloud.spanner.Type;
 import com.google.cloud.spanner.Type.StructField;
 import com.google.cloud.spanner.connection.Connection.InternalMetadataQuery;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableSet;
-import java.io.BufferedReader;
+import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
 import java.sql.Connection;
 import java.sql.DatabaseMetaData;
 import java.sql.ResultSet;
@@ -40,6 +44,8 @@
 import java.util.Collections;
 import java.util.Properties;
 import java.util.Scanner;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 
 /** {@link DatabaseMetaData} implementation for Cloud Spanner */
 class JdbcDatabaseMetaData extends AbstractJdbcWrapper implements DatabaseMetaData {
@@ -50,24 +56,36 @@ class JdbcDatabaseMetaData extends AbstractJdbcWrapper implements DatabaseMetaDa
   private static final String PRODUCT_NAME = "Google Cloud Spanner";
   private static final String POSTGRESQL_PRODUCT_NAME = PRODUCT_NAME + " PostgreSQL";
 
+  private static final ConcurrentMap<String, String> SQL_CACHE = new ConcurrentHashMap<>();
+
   @VisibleForTesting
-  static String readSqlFromFile(String filename, Dialect dialect) {
-    InputStream in;
-    switch (dialect) {
-      case POSTGRESQL:
-        in = JdbcDatabaseMetaData.class.getResourceAsStream("postgresql/" + filename);
-        break;
-      case GOOGLE_STANDARD_SQL:
-      default:
-        in = JdbcDatabaseMetaData.class.getResourceAsStream(filename);
+  static String readSqlFromFile(String filename, Dialect dialect) throws SQLException {
+    try {
+      return SQL_CACHE.computeIfAbsent(
+          filename + "/" + dialect, (key) -> loadSqlFromFile(filename, dialect));
+    } catch (SpannerException e) {
+      throw JdbcSqlExceptionFactory.of(e);
+    }
+  }
+
+  private static String loadSqlFromFile(String filename, Dialect dialect) {
+    String resourcePath = dialect == Dialect.POSTGRESQL ? "postgresql/" + filename : filename;
+    InputStream in = JdbcDatabaseMetaData.class.getResourceAsStream(resourcePath);
+    if (in == null) {
+      throw SpannerExceptionFactory.newSpannerException(
+          ErrorCode.NOT_FOUND, "Resource not found: " + resourcePath);
     }
-    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
     StringBuilder builder = new StringBuilder();
-    try (Scanner scanner = new Scanner(reader)) {
+    try (InputStream input = in;
+        InputStreamReader reader = new InputStreamReader(input, StandardCharsets.UTF_8);
+        Scanner scanner = new Scanner(reader)) {
       while (scanner.hasNextLine()) {
         String line = scanner.nextLine();
         builder.append(line).append("\n");
       }
+    } catch (IOException e) {
+      throw SpannerExceptionFactory.newSpannerException(
+          ErrorCode.INTERNAL, "Could not read SQL file " + resourcePath, e);
     }
     return builder.toString();
   }

java-spanner-jdbc/src/test/java/com/google/cloud/spanner/jdbc/JdbcDatabaseMetaDataTest.java

@@ -19,6 +19,8 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
@@ -574,4 +576,21 @@ public void testGetUserName() throws SQLException, IOException {
     DatabaseMetaData meta = new JdbcDatabaseMetaData(connection);
     assertEquals("test@test-project.iam.gserviceaccount.com", meta.getUserName());
   }
+
+  @Test
+  public void testReadSqlFromFileCaching() throws SQLException {
+    String sql1 = JdbcDatabaseMetaData.readSqlFromFile("DatabaseMetaData_GetTables.sql", dialect);
+    String sql2 = JdbcDatabaseMetaData.readSqlFromFile("DatabaseMetaData_GetTables.sql", dialect);
+    assertNotNull(sql1);
+    assertSame(sql1, sql2);
+  }
+
+  @Test
+  public void testReadSqlFromFileNotFound() {
+    SQLException exception =
+        assertThrows(
+            SQLException.class,
+            () -> JdbcDatabaseMetaData.readSqlFromFile("NonExistent.sql", dialect));
+    assertTrue(exception.getMessage().contains("Resource not found"));
+  }
 }