feat(bigquery-jdbc): expose BigQueryResultSetMetadata and getField(int)

java-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/jdbc/BigQueryResultSetMetadata.java

@@ -27,7 +27,7 @@
 import java.sql.Types;
 
 /** This class returns ResultSetMetadata for the JSON and the Arrow ResultSets */
-class BigQueryResultSetMetadata implements ResultSetMetaData {
+public class BigQueryResultSetMetadata implements ResultSetMetaData {
   private static final BigQueryJdbcResultSetLogger LOG =
       BigQueryJdbcResultSetLogger.getLogger(BigQueryResultSetMetadata.class);
   private final FieldList schemaFieldList;
@@ -53,11 +53,21 @@ BigQueryStatement getStatement() {
     return this.statement;
   }
 
-  private Field getField(int sqlColumn) {
+  /**
+   * Returns the BigQuery {@link Field} schema definition for the given 1-based SQL column index.
+   *
+   * @param sqlColumn the first column is 1, the second is 2, ...
+   * @return the {@link Field} for the specified column
+   * @throws SQLException if the column index is out of bounds
+   */
+  public Field getField(int sqlColumn) throws SQLException {
+    if (sqlColumn < 1 || sqlColumn > this.columnCount) {
+      throw new BigQueryJdbcException("Column index out of bounds: " + sqlColumn);
+    }
     return this.schemaFieldList.get(sqlColumn - 1);
   }
 
-  private boolean isPicosecondTimestampColumn(int sqlColumn) {
+  private boolean isPicosecondTimestampColumn(int sqlColumn) throws SQLException {
     if (!this.enableTimestampPicos) {
       return false;
     }
@@ -77,7 +87,7 @@ public boolean isAutoIncrement(int column) {
   }
 
   @Override
-  public boolean isCaseSensitive(int column) {
+  public boolean isCaseSensitive(int column) throws SQLException {
     int colType = getColumnType(column);
     return colType == Types.NVARCHAR;
   }
@@ -93,7 +103,7 @@ public boolean isCurrency(int column) {
   }
 
   @Override
-  public int isNullable(int column) {
+  public int isNullable(int column) throws SQLException {
     Mode colMode = getField(column).getMode();
     if (colMode == null) {
       return ResultSetMetaData.columnNullableUnknown;
@@ -104,7 +114,7 @@ public int isNullable(int column) {
   }
 
   @Override
-  public boolean isSigned(int column) {
+  public boolean isSigned(int column) throws SQLException {
     int colType = getColumnType(column);
     return colType == Types.FLOAT
         || colType == Types.DOUBLE
@@ -113,7 +123,7 @@ public boolean isSigned(int column) {
   }
 
   @Override
-  public int getColumnDisplaySize(int column) {
+  public int getColumnDisplaySize(int column) throws SQLException {
     if (isPicosecondTimestampColumn(column)) {
       return 32;
     }
@@ -136,17 +146,17 @@ public int getColumnDisplaySize(int column) {
   }
 
   @Override
-  public String getColumnLabel(int column) {
+  public String getColumnLabel(int column) throws SQLException {
     return getField(column).getName();
   }
 
   @Override
-  public String getColumnName(int column) {
+  public String getColumnName(int column) throws SQLException {
     return getField(column).getName();
   }
 
   @Override
-  public int getPrecision(int column) {
+  public int getPrecision(int column) throws SQLException {
     Long precision = getField(column).getPrecision();
     if (precision != null) {
       return precision.intValue();
@@ -163,7 +173,7 @@ public int getPrecision(int column) {
   }
 
   @Override
-  public int getScale(int column) {
+  public int getScale(int column) throws SQLException {
     Long scale = getField(column).getScale();
     if (scale != null) {
       return scale.intValue();
@@ -196,7 +206,7 @@ public String getSchemaName(int column) {
     return ""; // not applicable
   }
 
-  private StandardSQLTypeName getStandardSQLTypeName(int column) {
+  private StandardSQLTypeName getStandardSQLTypeName(int column) throws SQLException {
     Field field = getField(column);
     if (field.getMode() == Mode.REPEATED) {
       return StandardSQLTypeName.ARRAY;
@@ -205,15 +215,15 @@ private StandardSQLTypeName getStandardSQLTypeName(int column) {
   }
 
   @Override
-  public int getColumnType(int column) {
+  public int getColumnType(int column) throws SQLException {
     if (isPicosecondTimestampColumn(column)) {
       return Types.VARCHAR;
     }
     return BigQueryTypeRegistry.toJdbcType(getStandardSQLTypeName(column));
   }
 
   @Override
-  public String getColumnTypeName(int column) {
+  public String getColumnTypeName(int column) throws SQLException {
     if (isPicosecondTimestampColumn(column)) {
       return BigQueryTemporalUtility.TIMESTAMP_PICOSECONDS_TYPE_NAME;
     }

java-bigquery-jdbc/src/test/java/com/google/cloud/bigquery/jdbc/BigQueryResultSetMetadataTest.java

@@ -271,6 +271,13 @@ public void testWrapperMethods() throws SQLException {
     assertThat(unwrappedImpl).isNotSameInstanceAs(resultSetMetaData);
     assertThat(unwrappedImpl).isInstanceOf(BigQueryResultSetMetadata.class);
 
+    BigQueryResultSetMetadata bqMetaData =
+        resultSetMetaData.unwrap(BigQueryResultSetMetadata.class);
+    assertThat(bqMetaData.getField(1)).isEqualTo(fieldList.get(0));
+    assertThat(bqMetaData.getField(8).getMode()).isEqualTo(Field.Mode.REPEATED);
+    assertThrows(SQLException.class, () -> bqMetaData.getField(0));
+    assertThrows(SQLException.class, () -> bqMetaData.getField(fieldList.size() + 1));
+
     BigQueryJdbcException e =
         assertThrows(
             BigQueryJdbcException.class, () -> resultSetMetaData.unwrap(java.sql.Connection.class));