makssent commented on PR #39081:
URL: https://github.com/apache/shardingsphere/pull/39081#issuecomment-4956605653
I've also been working on BLOB support in the Firebird proxy (#39050). The
original issue only covered `op_seek_blob`, but since this PR implements the
full BLOB flow, I'd like to share two bugs I ran into while testing BLOB
scenarios - both reproduce on this branch as well:
**1. The deferred BLOB handle `0xFFFF` (INVALID_OBJECT) is not resolved.**
Jaybird 5.0.7+ pipelines BLOB operations: it sends `op_put_segment` /
`op_info_blob` / `op_get_segment` right after `op_create_blob2` /
`op_open_blob2` without waiting for the response, using the placeholder
`0xFFFF` (`INVALID_OBJECT`) in place of the not-yet-known handle. The Firebird
server substitutes the handle of the most recently created object in this case,
while the proxy looks up `0xFFFF` literally:
- on write, `op_put_segment` finds no blob and silently drops the segment →
the row is inserted with **empty BLOBs**;
- on read, `op_get_segment` returns empty data and never reports the
end-of-blob state (`p_resp_object = 2`), so the client's read loop **never
terminates**.
Reproducible with Jaybird 5.0.10: INSERT stores empty BLOBs, and a
subsequent SELECT of a BLOB column hangs.
**2. The `op_get_segment` response declares the alignment padding as part of
the data.**
The response data must be `[2-byte little-endian length][segment bytes]`,
with the 4-byte alignment padding written **outside** the declared length.
Currently the declared length includes the padding, so Jaybird reads the
padding as data and runs past the buffer on any segment whose length % 4 == 1
or 3:
```
java.lang.ArrayIndexOutOfBoundsException: Index 26 out of bounds for length
26
at org.firebirdsql.gds.VaxEncoding.iscVaxInteger2(VaxEncoding.java:165)
at
org.firebirdsql.gds.ng.wire.version10.V10InputBlob.getSegment(V10InputBlob.java:136)
at
org.firebirdsql.jdbc.field.FBBlobField.getBytesInternal(FBBlobField.java:149)
```
Reproducible with Jaybird 5.0.6 by reading back a 21-byte BLOB (2 + 21 = 23
bytes of payload, 3 bytes of padding, declared length 26). Segments whose
length % 4 == 0 or 2 survive by luck — that's why small ASCII test payloads
often pass. Large BLOBs always fail: the client requests chunks of 32765 bytes
(32765 % 4 == 1).
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