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perf(spanner-jdbc): cache JDBC metadata query strings #14041

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perf(spanner-jdbc): cache JDBC metadata query strings #14041

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25 changes: 15 additions & 10 deletions java-spanner-jdbc/src/main/java/com/google/cloud/spanner/jdbc/JdbcDatabaseMetaData.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,10 +26,12 @@
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.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import java.io.BufferedReader;
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;
Expand All @@ -40,6 +42,8 @@
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 {
Expand All @@ -50,18 +54,19 @@ 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);
}
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
return SQL_CACHE.computeIfAbsent(
filename + "/" + dialect, (key) -> loadSqlFromFile(filename, dialect));
}

private static String loadSqlFromFile(String filename, Dialect dialect) {
String resourcePath = dialect == Dialect.POSTGRESQL ? "postgresql/" + filename : filename;
InputStream in = JdbcDatabaseMetaData.class.getResourceAsStream(resourcePath);
Preconditions.checkNotNull(in, "Resource not found: " + resourcePath);
BufferedReader reader = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8));
StringBuilder builder = new StringBuilder();
try (Scanner scanner = new Scanner(reader)) {
Comment on lines +69 to 71

@gemini-code-assist gemini-code-assist Bot Aug 11, 2026

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medium

To prevent potential resource leaks and ensure exception safety, all closeable resources (InputStream, InputStreamReader, and Scanner) should be managed within the try-with-resources block. If an exception occurs during the initialization of BufferedReader or Scanner, the underlying InputStream might not be closed. Additionally, BufferedReader is redundant here because Scanner performs its own buffering.

    StringBuilder builder = new StringBuilder();
    try (InputStream input = in;
        InputStreamReader reader = new InputStreamReader(input, StandardCharsets.UTF_8);
        Scanner scanner = new Scanner(reader)) {
References
  1. When managing a collection of closeable resources, ensure they are closed in the reverse order of their creation (LIFO). The implementation must be exception-safe to prevent resource leaks, meaning all opened resources should be closed even if exceptions occur during their creation or closing.

while (scanner.hasNextLine()) {
Expand Down
9 changes: 9 additions & 0 deletions java-spanner-jdbc/src/test/java/com/google/cloud/spanner/jdbc/JdbcDatabaseMetaDataTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
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.assertTrue;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
Expand Down Expand Up @@ -574,4 +575,12 @@ public void testGetUserName() throws SQLException, IOException {
DatabaseMetaData meta = new JdbcDatabaseMetaData(connection);
assertEquals("test@test-project.iam.gserviceaccount.com", meta.getUserName());
}

@Test
public void testReadSqlFromFileCaching() {
String sql1 = JdbcDatabaseMetaData.readSqlFromFile("DatabaseMetaData_GetTables.sql", dialect);
String sql2 = JdbcDatabaseMetaData.readSqlFromFile("DatabaseMetaData_GetTables.sql", dialect);
assertNotNull(sql1);
assertSame(sql1, sql2);
}
}
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