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Merge pull request #1700 from sylph-eu/implement_get_metadata_for_non_executed_query
[clickhouse-jdbc] describe SELECT queries to retrieve metadata
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‎CHANGELOG.md‎

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## Latest
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### New Features
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- Describe non-executed SELECT queries in prepared statements to provide metadata (https://github.com/ClickHouse/clickhouse-java/issues/1430)
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## 0.6.1
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### New Features

‎clickhouse-jdbc/src/main/java/com/clickhouse/jdbc/ClickHousePreparedStatement.java‎

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@@ -109,7 +109,17 @@ default void setClob(int parameterIndex, Clob x) throws SQLException {
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@Override
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default ResultSetMetaData getMetaData() throws SQLException {
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ResultSet currentResult = getResultSet();
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return currentResult != null ? currentResult.getMetaData() : null;
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if (currentResult != null) {
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return currentResult.getMetaData();
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} else if (getLargeUpdateCount() != -1L) {
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return null; // Update query
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}
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return describeQueryResult();
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}
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default ResultSetMetaData describeQueryResult() throws SQLException {
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return null;
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}
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@Override

‎clickhouse-jdbc/src/main/java/com/clickhouse/jdbc/internal/SqlBasedPreparedStatement.java‎

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import java.sql.Date;
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import java.sql.ParameterMetaData;
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import java.sql.ResultSet;
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import java.sql.ResultSetMetaData;
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import java.sql.SQLException;
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import java.sql.Statement;
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import java.sql.Time;
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import java.sql.Timestamp;
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import java.time.LocalDate;
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import com.clickhouse.data.value.ClickHouseStringValue;
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import com.clickhouse.logging.Logger;
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import com.clickhouse.logging.LoggerFactory;
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import com.clickhouse.jdbc.ClickHouseConnection;
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import com.clickhouse.jdbc.ClickHousePreparedStatement;
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import com.clickhouse.jdbc.ClickHouseResultSetMetaData;
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import com.clickhouse.jdbc.JdbcParameterizedQuery;
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import com.clickhouse.jdbc.SqlExceptionUtils;
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import com.clickhouse.jdbc.parser.ClickHouseSqlStatement;
@@ -239,6 +243,42 @@ protected int getMaxParameterIndex() {
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return templates.length;
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}
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@Override
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public ResultSetMetaData describeQueryResult() throws SQLException {
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// No metadata unless query has been recognized as SELECT
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if (!parsedStmt.isRecognized() || !parsedStmt.isQuery()) {
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return null;
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}
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final String[] vals;
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if (batch.isEmpty()) {
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vals = new String[values.length];
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System.arraycopy(this.values, 0, vals, 0, values.length);
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} else {
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vals = batch.get(0);
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}
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for (int i = 0; i < values.length; i++) {
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if (vals[i] == null) {
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vals[i] = ClickHouseValues.NULL_EXPR;
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}
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}
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StringBuilder sb = new StringBuilder("desc (");
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preparedQuery.apply(sb, vals);
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sb.append(')');
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List<ClickHouseColumn> columns = new LinkedList<>();
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ClickHouseConnection conn = getConnection();
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try (Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery(sb.toString())) {
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while (rs.next()) {
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columns.add(ClickHouseColumn.of(rs.getString(1), rs.getString(2)));
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}
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}
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return ClickHouseResultSetMetaData.of(conn.getJdbcConfig(), conn.getCurrentDatabase(), "",
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Collections.unmodifiableList(new ArrayList<>(columns)), mapper, conn.getTypeMap());
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}
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@Override
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public ResultSet executeQuery() throws SQLException {
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ensureParams();

‎clickhouse-jdbc/src/test/java/com/clickhouse/jdbc/ClickHousePreparedStatementTest.java‎

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import java.io.File;
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import java.io.IOException;
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import java.math.BigDecimal;
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import java.math.BigInteger;
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import java.net.Inet4Address;
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import java.net.Inet6Address;
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import java.net.MalformedURLException;
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import java.sql.ParameterMetaData;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.ResultSetMetaData;
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import java.sql.SQLException;
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import java.sql.Statement;
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import java.sql.Timestamp;
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}
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}
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@Test(groups = "integration")
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public void testGetMetadataTypes() throws SQLException {
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try (Connection conn = newConnection(new Properties());
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PreparedStatement ps = conn.prepareStatement("select ? a, ? b")) {
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ResultSetMetaData md = ps.getMetaData();
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Assert.assertEquals(md.getColumnCount(), 2);
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Assert.assertEquals(md.getColumnName(1), "a");
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Assert.assertEquals(md.getColumnTypeName(1), "Nullable(Nothing)");
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Assert.assertEquals(md.getColumnName(2), "b");
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Assert.assertEquals(md.getColumnTypeName(2), "Nullable(Nothing)");
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ps.setString(1, "x");
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md = ps.getMetaData();
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Assert.assertEquals(md.getColumnCount(), 2);
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Assert.assertEquals(md.getColumnName(1), "a");
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Assert.assertEquals(md.getColumnTypeName(1), "String");
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Assert.assertEquals(md.getColumnName(2), "b");
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Assert.assertEquals(md.getColumnTypeName(2), "Nullable(Nothing)");
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ps.setObject(2, new BigInteger("12345"));
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md = ps.getMetaData();
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Assert.assertEquals(md.getColumnCount(), 2);
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Assert.assertEquals(md.getColumnName(1), "a");
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Assert.assertEquals(md.getColumnTypeName(1), "String");
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Assert.assertEquals(md.getColumnName(2), "b");
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Assert.assertEquals(md.getColumnTypeName(2), "UInt16");
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ps.addBatch();
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ps.setInt(1, 2);
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md = ps.getMetaData();
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Assert.assertEquals(md.getColumnCount(), 2);
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Assert.assertEquals(md.getColumnName(1), "a");
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Assert.assertEquals(md.getColumnTypeName(1), "String");
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Assert.assertEquals(md.getColumnName(2), "b");
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Assert.assertEquals(md.getColumnTypeName(2), "UInt16");
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ps.clearBatch();
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ps.clearParameters();
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md = ps.getMetaData();
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Assert.assertEquals(md.getColumnCount(), 2);
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Assert.assertEquals(md.getColumnName(1), "a");
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Assert.assertEquals(md.getColumnTypeName(1), "Nullable(Nothing)");
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Assert.assertEquals(md.getColumnName(2), "b");
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Assert.assertEquals(md.getColumnTypeName(2), "Nullable(Nothing)");
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}
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}
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@Test(groups = "integration")
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public void testGetMetadataStatements() throws SQLException {
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try (Connection conn = newConnection(new Properties());
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PreparedStatement createPs = conn.prepareStatement("create table test_get_metadata_statements (col String) Engine=Log");
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PreparedStatement selectPs = conn.prepareStatement("select 'Hello, World!'");
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PreparedStatement insertPs = conn.prepareStatement(
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"insert into test_get_metadata_statements select 'Hello, World!'");
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PreparedStatement updatePs = conn.prepareStatement(
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"update test_get_metadata_statements set col = 'Bye, World!'");
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PreparedStatement grantPs = conn.prepareStatement("grant select on * to default");
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PreparedStatement commitPS = conn.prepareStatement("commit");) {
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// Only select shall have valid metadata
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ResultSetMetaData selectMetaData = selectPs.getMetaData();
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Assert.assertNotNull(selectMetaData);
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Assert.assertEquals(selectMetaData.getColumnCount(), 1);
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Assert.assertEquals(selectMetaData.getColumnTypeName(1), "String");
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// The rest shall return null
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Assert.assertNull(createPs.getMetaData());
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Assert.assertNull(insertPs.getMetaData());
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Assert.assertNull(updatePs.getMetaData());
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Assert.assertNull(grantPs.getMetaData());
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Assert.assertNull(commitPS.getMetaData());
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}
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}
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@Test(groups = "integration")
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public void testGetParameterMetaData() throws SQLException {
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try (Connection conn = newConnection(new Properties());

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