apache/shardingsphere · error · FirebirdProtocolException

Unknown blob information request type %d

Error message

Unknown blob information request type %d

What it means

Thrown when a Firebird client requests blob information and the requested info item is not one of the four handled types (NUM_SEGMENTS, MAX_SEGMENT, TOTAL_LENGTH, TYPE). The Firebird protocol defines many isc_info_blob_* items; this implementation covers only the subset above, and any other item code hits the default branch and throws.

Source

Thrown at database/protocol/dialect/firebird/src/main/java/org/apache/shardingsphere/database/protocol/firebird/packet/command/query/info/type/blob/FirebirdBlobInfoReturnPacket.java:71

            }
        }
        FirebirdCommonInfoPacketType.parseCommonInfo(payload, FirebirdCommonInfoPacketType.END);
    }
    
    private void parseBlobInfo(final FirebirdPacketPayload payload, final FirebirdBlobInfoPacketType type) {
        switch (type) {
            case NUM_SEGMENTS:
                writeIntValue(payload, type, getSegmentCount());
                return;
            case MAX_SEGMENT:
            case TOTAL_LENGTH:
                writeIntValue(payload, type, getSegmentLength());
                return;
            case TYPE:
                writeIntValue(payload, type, BLOB_TYPE_SEGMENTED);
                return;
            default:
                throw new FirebirdProtocolException("Unknown blob information request type %d", type.getCode());
        }
    }
    
    private void writeIntValue(final FirebirdPacketPayload payload, final FirebirdBlobInfoPacketType type, final int value) {
        payload.writeInt1(type.getCode());
        payload.writeInt2LE(4);
        payload.writeInt4LE(value);
    }
    
    private int getSegmentLength() {
        return blobLength;
    }
    
    private int getSegmentCount() {
        return 0 == blobLength ? 0 : 1;
    }
}

View on GitHub (pinned to e952770a21)

Solutions

  1. Identify the numeric item code in the message and map it to the isc_info_blob_* constant in Firebird's ibase.h
  2. Restrict client-side blob info requests to NUM_SEGMENTS, MAX_SEGMENT, TOTAL_LENGTH, and TYPE
  3. Contribute a handler for the missing item in FirebirdBlobInfoReturnPacket (write item code, 2-byte LE length, value) and raise it upstream
  4. As a workaround, fetch the blob stream directly instead of querying its info metadata

Example fix

// before: client requests an unimplemented blob info item
// (e.g. isc_info_blob_collation = 15)

// after: only request supported items
// int[] supported = { isc_info_blob_num_segments, isc_info_blob_max_segment,
//                     isc_info_blob_total_length, isc_info_blob_type };
Defensive patterns

Strategy: validation

Validate before calling

// before calling blob info, restrict to implemented items
private static final Set<Integer> SUPPORTED_BLOB_INFO = Set.of(
        FirebirdBlobInfoPacketType.NUM_SEGMENTS.getCode(),
        FirebirdBlobInfoPacketType.MAX_SEGMENT.getCode(),
        FirebirdBlobInfoPacketType.TOTAL_LENGTH.getCode(),
        FirebirdBlobInfoPacketType.TYPE.getCode());

int item = /* requested item */ 0;
if (!SUPPORTED_BLOB_INFO.contains(item)) {
    // degrade gracefully instead of triggering the throw
    return Optional.empty();
}

Type guard

static boolean isSupportedBlobInfoItem(final int code) {
    return code == FirebirdBlobInfoPacketType.NUM_SEGMENTS.getCode()
        || code == FirebirdBlobInfoPacketType.MAX_SEGMENT.getCode()
        || code == FirebirdBlobInfoPacketType.TOTAL_LENGTH.getCode()
        || code == FirebirdBlobInfoPacketType.TYPE.getCode();
}

Try / catch

try {
    packet.write(payload);
} catch (FirebirdProtocolException ex) {
    // unknown info item: respond with isc_info_error / skip the item rather than killing the session if your layer can
    log.warn("unsupported blob info item: {}", ex.getMessage());
}

Prevention

When it happens

Trigger: Calling isc_blob_info with items such as isc_info_blob_collation or any item beyond NUM_SEGMENTS/MAX_SEGMENT/TOTAL_LENGTH/TYPE, causing FirebirdBlobInfoReturnPacket.write() to fall into the default case.

Common situations: Using a Firebird client/driver feature (e.g. Jaybird's metadata calls) that queries blob info items this proxy does not implement yet; upgrading a client that newly requests extra items.

Related errors

AI-assisted analysis of apache/shardingsphere@e952770a21 (2026-08-14). Data as JSON: /api/errors/fecb7ed81af7884d. Report an issue: GitHub.