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MCAP cli produces empty message index #862
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Internal tracking ticket: FG-2527 |
Hi, thanks for the bug report, however, the "steps to reproduce" section is lacking. Can you provide more information about how one can see that this issue has occurred? And can you provide more detail about what slowdown you have observed? |
Sorry for the unclear explanation, for example the slow down occures in the following code: with open(sys.argv[1], "rb") as f:
reader = make_reader(f)
for schema, channel, message in reader.iter_messages(topics=["/tf_static"]):
print(f"{channel.topic} ({schema.name}): {message.data}") even after printing all I've checked the record Length of the MessageIndex here mcap/python/mcap/mcap/reader.py Lines 84 to 86 in 0842cbf
which showed that a MessageIndex for /tf_static exists for all chunks but the record length is almost always zero.
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The code snippet is helpful, can you share an example file as well? |
### Public-Facing Changes Go MCAP writer no longer produces message index records for channels not present in a chunk. This helps indexed readers skip chunks that do not contain any messages on a given channel. ### Description Fixes #862
Description
The MCAP cli produces an empty message index instead of omitting it. It seems that this slows down Foxglove and the Python lib.
Steps To Reproduce
mcap compress
on any fileExpected Behavior
no message index at all for topics not in this chunk
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