{"record":{"id":"d7cbb49de05d64cc","repo":"apache/flink","slug":"unknown-field-name-s-for-mapping-to-a-position","errorCode":null,"errorMessage":"Unknown field name '%s' for mapping to a position.","messagePattern":"Unknown field name '(.+?)' for mapping to a position\\.","errorType":"exception","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"flink-core/src/main/java/org/apache/flink/types/Row.java","lineNumber":291,"sourceCode":"    public <T> T getFieldAs(int pos) {\n        return (T) getField(pos);\n    }\n\n    /**\n     * Returns the field's content using the specified field name.\n     *\n     * <p>Note: The row must operate in name-based field mode.\n     *\n     * @param name the name of the field or null if not set previously\n     * @return the field's content\n     */\n    public @Nullable Object getField(String name) {\n        if (fieldByName != null) {\n            return fieldByName.get(name);\n        } else if (positionByName != null) {\n            final Integer pos = positionByName.get(name);\n            if (pos == null) {\n                throw new IllegalArgumentException(\n                        String.format(\"Unknown field name '%s' for mapping to a position.\", name));\n            }\n            assert fieldByPosition != null;\n            return fieldByPosition[pos];\n        } else {\n            throw new IllegalArgumentException(\n                    \"Accessing a field by name is not supported in position-based field mode.\");\n        }\n    }\n\n    /**\n     * Returns the field's content using the specified field name.\n     *\n     * <p>Note: The row must operate in name-based field mode.\n     *\n     * <p>This method avoids a lot of manual casting in the user implementation.\n     *\n     * @param name the name of the field, set previously","sourceCodeStart":273,"sourceCodeEnd":309,"githubUrl":"https://github.com/apache/flink/blob/2f3c205e9266cb30240eb7f4fdab15cad629a70f/flink-core/src/main/java/org/apache/flink/types/Row.java#L273-L309","documentation":"In Row's hybrid mode (created with positions plus a name-to-position mapping, positionByName != null), getField(String name) looks the name up in positionByName; if the map has no entry for the given string, it throws this IllegalArgumentException listing the unknown name. The row knows its field positions but not the requested label.","triggerScenarios":"Calling getField(name) on a hybrid Row (built with Row.withPosition(...)-style APIs that attach names) where name is not among the attached names — e.g. a typo, case mismatch, or a name from a different schema version.","commonSituations":"Schema evolution where a field was renamed; connectors mapping external column names to Row fields with slightly different casing; copy-paste of field name strings between classes.","solutions":["Use one of the row's actual field names: check row.getFieldNames(true) or the exception's available-names message (setField lists them)","For lookups that may legitimately miss, check containsField-style via getFieldNames before calling getField","Centralize field-name constants instead of scattering string literals"],"exampleFix":"// before\nObject v = row.getField(\"userName\"); // attached name is \"user_name\"\n\n// after\nObject v = row.getField(\"user_name\");\n// or guard:\nif (row.getFieldNames(true).contains(\"userName\")) { ... }","handlingStrategy":"validation","validationCode":"List<String> names = row.getFieldNames(true);\nif (names == null || !names.contains(fieldName)) {\n    throw new IllegalArgumentException(\"Unknown field '\" + fieldName + \"'; known: \" + names);\n}\nrow.getField(fieldName);","typeGuard":"static boolean hasField(Row row, String name) {\n    List<String> names = row.getFieldNames(true);\n    return names != null && names.contains(name);\n}","tryCatchPattern":"catch (IllegalArgumentException e) { // log available names from e.getMessage(), fix mapping }","preventionTips":["Share field-name constants between writer and reader","Watch casing conventions","The exception for setField lists available names — read it"],"tags":["flink","row","field-name","illegal-argument","schema-mismatch"],"backgroundTag":null,"analyzedSha":"2f3c205e9266cb30240eb7f4fdab15cad629a70f","analyzedAt":"2026-08-14T08:48:24.518Z","schemaVersion":2},"datasetVersion":"2026-08-14T10:17:34.591Z"}