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

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.connection.AbstractStatementParser;
 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 = AbstractStatementParser.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

@@ -24,6 +24,7 @@
 import com.google.cloud.spanner.SpannerException;
 import com.google.cloud.spanner.Statement;
 import com.google.cloud.spanner.Type;
+import com.google.cloud.spanner.connection.AbstractStatementParser;
 import com.google.cloud.spanner.connection.AbstractStatementParser.ParametersInfo;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
@@ -74,7 +75,9 @@ 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(AbstractStatementParser.getParameterName(index)), index);
     }
     return builder.build();
   }

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

@@ -347,7 +347,7 @@ 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(AbstractStatementParser.getParameterName(index++), Value.toValue(value));
       }
       return parameters;
     }

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

@@ -750,6 +750,31 @@ private String removeOpeningBrackets(String sql) {
   static final ReadQueryUpdateTransactionOption[] EMPTY_OPTIONS =
       new ReadQueryUpdateTransactionOption[0];
 
+  private static final int MAX_PRECOMPUTED_PARAM_INDEX = 256;
+  private static final String[] PRECOMPUTED_P_PARAM_NAMES =
+      new String[MAX_PRECOMPUTED_PARAM_INDEX + 1];
+
+  static {
+    for (int i = 1; i <= MAX_PRECOMPUTED_PARAM_INDEX; i++) {
+      PRECOMPUTED_P_PARAM_NAMES[i] = "p" + i;
+    }
+  }
+
+  /**
+   * Returns the parameter name for the given 1-based parameter index with the standard 'p' prefix
+   * (e.g. "p1", "p2").
+   *
+   * <p>Returns pre-allocated strings for indices between 1 and 256 to avoid heap allocations in hot
+   * parameter binding loops.
+   */
+  @InternalApi
+  public static String getParameterName(int index) {
+    if (index > 0 && index <= MAX_PRECOMPUTED_PARAM_INDEX) {
+      return PRECOMPUTED_P_PARAM_NAMES[index];
+    }
+    return "p" + 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/connection/StatementParserTest.java

@@ -20,6 +20,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -1864,6 +1865,19 @@ public void testStatementCache_ParameterizedStatement() {
     assertEquals(1, stats.hitCount());
   }
 
+  @Test
+  public void testGetParameterName() {
+    for (int i = 1; i <= 256; i++) {
+      assertEquals("p" + i, AbstractStatementParser.getParameterName(i));
+      assertSame(
+          AbstractStatementParser.getParameterName(i), AbstractStatementParser.getParameterName(i));
+    }
+    assertEquals("p257", AbstractStatementParser.getParameterName(257));
+    assertEquals("p1000", AbstractStatementParser.getParameterName(1000));
+    assertEquals("p0", AbstractStatementParser.getParameterName(0));
+    assertEquals("p-1", AbstractStatementParser.getParameterName(-1));
+  }
+
   @Test
   public void testClientSideStatementWithComment() {
     String sql = "-- Null (no timeout)\n" + "SET STATEMENT_TIMEOUT=null";