apache/seatunnel · warning

Skipping unsupported default value for column {} in table {}

Error message

Skipping unsupported default value for column {} in table {}.

What it means

During SQL Server schema-change (DDL) application, a column has a default value that the dialect cannot translate into a `ALTER TABLE ... ADD CONSTRAINT ... DEFAULT ... FOR <col>` clause, so the ADD-DEFAULT DDL is skipped and a warning is logged. The column is still created/modified; only its default value is not applied.

Source

Thrown at seatunnel-connectors-v2/connector-jdbc/src/main/java/org/apache/seatunnel/connectors/seatunnel/jdbc/internal/dialect/sqlserver/SqlServerDialect.java:423

                                        .append(quoteIdentifier(constraintName));
                        ddlSQL.add(dropConstraintSQL.toString());
                    }
                }

                // Process column default
                String defaultValueClause =
                        sqlClauseWithDefaultValue(typeDefine, sourceDialectName);
                if (StringUtils.isNotBlank(defaultValueClause)) {
                    StringBuilder defaultSqlBuilder =
                            buildAlterTablePrefix(tablePath)
                                    .append(" ADD ")
                                    .append(defaultValueClause)
                                    .append(" FOR ")
                                    .append(quoteIdentifier(column.getName()));
                    ddlSQL.add(defaultSqlBuilder.toString());
                }
            } else {
                log.warn(
                        "Skipping unsupported default value for column {} in table {}.",
                        column.getName(),
                        tablePath.getFullName());
            }
        }

        // Process column comment
        if (column.getComment() != null) {
            ddlSQL.add(buildColumnCommentSQL(tablePath, column));
        }

        // Build the SQL statement that modifies the column
        StringBuilder sqlBuilder =
                buildAlterTablePrefix(tablePath)
                        .append(" ALTER COLUMN ")
                        .append(quoteIdentifier(column.getName()))
                        .append(" ")
                        .append(columnType);

View on GitHub (pinned to cf67b549a7)

Solutions

1. Check the log to identify the column, then manually add the default in SQL Server: ALTER TABLE <t> ADD CONSTRAINT <c> DEFAULT <expr> FOR <col>.
2. Simplify the source column's default value to a plain literal that the dialect can render.
3. If the default is not needed for the sink, ignore the warning.
4. Upgrade/patch SqlServerDialect.defaultValueClause to support the missing default expression type.

Example fix

// before (source column with unsupported default)
Column.of("created", LocalDateTimeType()).withDefaultValue(...complex expression...)
// after
Column.of("created", LocalDateTimeType()).withDefaultValue(DefaultValue.of(null)) // or a literal; set the default manually in SQL Server

// Before running schema evolution, check every column's default value is a plain literal:
boolean hasSupportedDefault(CatalogColumn c) {
  return c.getDefaultValue() == null || c.getDefaultValue().getValue() instanceof Number
      || c.getDefaultValue().getValue() instanceof String
      || c.getDefaultValue().getValue() instanceof Boolean;
}
columns.stream().filter(c -> !hasSupportedDefault(c)).forEach(c -> log.warn("Manual default needed for " + c.getName()));

boolean isPlainLiteralDefault(Object v) { return v == null || v instanceof Number || v instanceof String || v instanceof Boolean; }

When it happens

Trigger: Running schema evolution (applySchemaChange) on SQL Server when a CatalogColumn carries a defaultValue whose literal type or expression is not supported by SqlServerDialect's defaultValueClause builder (e.g. complex/function-based defaults, unsupported literal types).

Common situations: CDC/schema-evolution jobs syncing tables whose source columns have non-literal defaults (CURRENT_TIMESTAMP expressions, sequence defaults, bind variables); tables mirrored from other databases with exotic default expressions.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Error executing SqlServer SQL: ${ddlSQL}
• Column '{}' in table {} is NOT NULL but has no DEFAULT; addi
• Column {} already exists in table {}. Skipping change column
• Column {} already exists in table {}. Skipping add column op
• Column {} does not exist in table {}. Skipping drop column o

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/093cb3ed01bf01a8. Report an issue: GitHub.