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DuckDBAppender.append does not transcode from String automatically (1.3.1.0 -> 1.3.2.0) #326
Description
I consider a table with an INTEGER column, in which the appender write as String.
With DuckDB Java connector 1.3.1.0:
@Test
public void testInsertStringIntoInt_1310() throws SQLException {
DuckDBConnection duckDbC = (DuckDBConnection) DriverManager.getConnection("jdbc:duckdb:");
try (Statement s = duckDbC.createStatement()) {
s.execute("CREATE TABLE t (c INTEGER)");
}
DuckDBAppender appender = duckDbC.createAppender("main", "t");
appender.beginRow();
appender.append("123");
appender.endRow();
}
It works correctly. Writing as String relates to #163 as it appeared append(String) was resilient to handle various types.
With 1.3.2.0, the code fails with:
java.sql.SQLException: Appender error, catalog: 'null', schema: 'main', table: 't', message: invalid column type, expected one of: '[DUCKDB_TYPE_VARCHAR]', actual: 'DUCKDB_TYPE_INTEGER'
at org.duckdb.DuckDBAppender.checkColumnType(DuckDBAppender.java:1227)
at org.duckdb.DuckDBAppender.checkCurrentColumnType(DuckDBAppender.java:1214)
at org.duckdb.DuckDBAppender.checkCurrentColumnType(DuckDBAppender.java:1209)
at org.duckdb.DuckDBAppender.append(DuckDBAppender.java:916)
at eu.solven.adhoc.pivotable.app.TestAppenderStringToIntColumn.testInsertStringIntoInt_1310(TestAppenderStringToIntColumn.java:22)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
While the new behavior seems legitimate, it is unexpected. Is it a bug or a feature ? I would expected parsing from String to many types to still be a thing for edge-cases (e.g. double[][][]).
Here an example :
@Test
public void testInsertStringIntoInt_1310() throws SQLException {
DuckDBConnection conn = (DuckDBConnection) DriverManager.getConnection("jdbc:duckdb:");
try (Statement s = conn.createStatement()) {
s.execute("CREATE TABLE t (c INTEGER, arr INTEGER[2][2][2])");
}
try (DuckDBAppender appender2 = conn.createAppender("main", "t")) {
appender2.beginRow();
appender2.append("123");
appender2.append("[[[1, 2], [3, 4]],[[5, 6], [7, 8]]]");
appender2.endRow();
}
try (Statement s = conn.createStatement()) {
try (ResultSet rs = s.executeQuery("SELECT * FROM t")) {
while (rs.next()) {
System.out.println(rs.getString(1));
System.out.println(rs.getString(2));
}
}
}
}
In 1.3.2.0, appender2.append("123") can be turned into appender2.append(123) but I see no option for appender2.append("[[[1, 2], [3, 4]],[[5, 6], [7, 8]]]").
https://duckdb.org/docs/stable/clients/java.html#appender may be updated to
try (var appender = conn.createAppender("tbl")) {
appender.beginRow().append(10).append(3.2).append("hello").endRow();
appender.beginRow().append(20).append(-8.1).append("world").endRow();
}
given the new signatures.
Activity
[-]DuckDBAppender.append does not transcode from String automatically[/-][+]DuckDBAppender.append does not transcode from String automatically (1.3.1.0 -> 1.3.2.0)[/+]staticlibs commentedon Jul 30, 2025
@blacelle
Hi, thanks for the report! This behaviour is intentional,
append()methods use strict checks that the input type matches the column type. For exampleappend(int)will NOT work for theBIGINTcolumn.These checks can be relaxed for some type, but in general it is expected that values are prepared with correct types in client code.
If auto type casting is required for existing client code - the old Appender is still available through the
connection.createSingleValueAppender()call.staticlibs commentedon Sep 25, 2025
#399 adds support for nested
LISTs in Appender. While 3-dimentionalARRAYs are not supported, similar logic can be done using aLISTof 2-dimentional arrays.Closing the issue, please re-open if needed.