perf(spanner-jdbc): cache commonly used query parameter names (#14036)

Cache the most commonly used query parameter names for positional
parameters to prevent the creation of new strings for every single SQL
statement execution.

Author: olavloite

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

@@ -18,6 +18,7 @@
 
 import com.google.cloud.spanner.JdbcDataTypeConverter;
 import com.google.cloud.spanner.ResultSet;
+import com.google.cloud.spanner.Statement;
 import com.google.rpc.Code;
 import com.google.spanner.v1.StructType;
 import com.google.spanner.v1.StructType.Field;
@@ -44,7 +45,7 @@ class JdbcParameterMetaData extends AbstractJdbcWrapper implements ParameterMeta
 
   private Field getField(int param) throws SQLException {
     JdbcPreconditions.checkArgument(param > 0 && param <= parameters.getFieldsCount(), param);
-    String paramName = "p" + param;
+    String paramName = Statement.getParameterName(param);
     return parameters.getFieldsList().stream()
         .filter(field -> field.getName().equals(paramName))
         .findAny()

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

@@ -74,7 +74,7 @@ Statement createStatement() throws SQLException {
     ParametersInfo paramInfo = getParametersInfo();
     Statement.Builder builder = Statement.newBuilder(paramInfo.sqlWithNamedParameters);
     for (int index = 1; index <= getParameters().getHighestIndex(); index++) {
-      getParameters().bindParameterValue(builder.bind("p" + index), index);
+      getParameters().bindParameterValue(builder.bind(Statement.getParameterName(index)), index);
     }
     return builder.build();
   }

java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/Statement.java

@@ -19,6 +19,7 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 
+import com.google.api.core.InternalApi;
 import com.google.cloud.spanner.ReadContext.QueryAnalyzeMode;
 import com.google.cloud.spanner.connection.AbstractStatementParser;
 import com.google.cloud.spanner.connection.AbstractStatementParser.ParametersInfo;
@@ -63,6 +64,28 @@ public final class Statement implements Serializable {
   private final String sql;
   private final QueryOptions queryOptions;
 
+  private static final int MAX_PRECOMPUTED_PARAM_NAMES = 950;
+  private static final String[] PRECOMPUTED_P_PARAM_NAMES =
+      new String[MAX_PRECOMPUTED_PARAM_NAMES + 1];
+
+  static {
+    for (int index = 1; index <= MAX_PRECOMPUTED_PARAM_NAMES; index++) {
+      PRECOMPUTED_P_PARAM_NAMES[index] = "p" + index;
+    }
+  }
+
+  /**
+   * Returns the parameter name for the given 1-based index (e.g. "p1", "p2"). Precomputed string
+   * constants are returned for indices 1 to 950.
+   */
+  @InternalApi
+  public static String getParameterName(int index) {
+    if (index > 0 && index <= MAX_PRECOMPUTED_PARAM_NAMES) {
+      return PRECOMPUTED_P_PARAM_NAMES[index];
+    }
+    return "p" + index;
+  }
+
   private Statement(String sql, Map<String, Value> parameters, QueryOptions queryOptions) {
     this.sql = sql;
     this.parameters = parameters;
@@ -347,7 +370,7 @@ private Map<String, Value> getUnnamedParametersMap(Object[] values) {
       Map<String, Value> parameters = new HashMap<>();
       int index = 1;
       for (Object value : values) {
-        parameters.put("p" + (index++), Value.toValue(value));
+        parameters.put(getParameterName(index++), Value.toValue(value));
       }
       return parameters;
     }

java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/AbstractStatementParser.java

@@ -776,6 +776,17 @@ private String removeOpeningBrackets(String sql) {
   static final ReadQueryUpdateTransactionOption[] EMPTY_OPTIONS =
       new ReadQueryUpdateTransactionOption[0];
 
+  /**
+   * Returns the parameter name for the given 1-based parameter index with the standard 'p' prefix
+   * (e.g. "p1", "p2").
+   *
+   * <p>Delegates to {@link Statement#getParameterName(int)}.
+   */
+  @InternalApi
+  public static String getParameterName(int index) {
+    return Statement.getParameterName(index);
+  }
+
   /** Parameter information with positional parameters translated to named parameters. */
   @InternalApi
   public static class ParametersInfo {

java-spanner/google-cloud-spanner/src/test/java/com/google/cloud/spanner/StatementTest.java

@@ -21,6 +21,7 @@
 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.assertThrows;
 
 import com.google.cloud.ByteArray;
@@ -185,4 +186,18 @@ public void equalsAndHashCode() {
         Statement.newBuilder("SELECT @x, @y").bind("x").to((Value) null).build());
     tester.testEquals();
   }
+
+  @Test
+  public void testGetParameterName() {
+    assertEquals("p1", Statement.getParameterName(1));
+    assertEquals("p950", Statement.getParameterName(950));
+    assertEquals("p951", Statement.getParameterName(951));
+    assertEquals("p0", Statement.getParameterName(0));
+    assertEquals("p-1", Statement.getParameterName(-1));
+
+    // Verify instance caching for indices 1..950
+    for (int i = 1; i <= 950; i++) {
+      assertSame(Statement.getParameterName(i), Statement.getParameterName(i));
+    }
+  }
 }

java-spanner/google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/StatementParserTest.java

@@ -1866,6 +1866,19 @@ public void testStatementCache_ParameterizedStatement() {
     assertEquals(1, stats.hitCount());
   }
 
+  @Test
+  public void testGetParameterName() {
+    for (int i = 1; i <= 950; i++) {
+      assertEquals("p" + i, AbstractStatementParser.getParameterName(i));
+      assertSame(
+          AbstractStatementParser.getParameterName(i), AbstractStatementParser.getParameterName(i));
+    }
+    assertEquals("p951", AbstractStatementParser.getParameterName(951));
+    assertEquals("p1000", AbstractStatementParser.getParameterName(1000));
+    assertEquals("p0", AbstractStatementParser.getParameterName(0));
+    assertEquals("p-1", AbstractStatementParser.getParameterName(-1));
+  }
+
   @Test
   public void testPositionalParametersCache() {
     CacheStats statsBefore = parser.getPositionalParametersCacheStats();