The good news is that I believe I have found a way around the problem.
The bad news is that I think I have found another minor bug.
The workaround for variable message sizes is to compute the "used"
buffer size after each call to IBatch::add by ensuring that
getAlignedLength() is refreshed for each message buffer and adding this
to the running total. It is then possible to identify when the buffer
will overflow before IBatch::add is called and take appropriate action.
The minor bug is that if TAG_BUFFER_BYTES_SIZE is set to > 256MB no
error status is reported on a call to createBatch. Instead, you only
know you have a problem when an error is returned from IBatch::add -
looks like the buffer size is simply limited to 256MB.
On 21/08/2021 12:35, Tony Whyman wrote:
On 20/08/2021 16:18, Alex Peshkoff via Firebird-devel wrote:
On 8/20/21 4:01 PM, Tony Whyman wrote:
You can specify such limit - use IBatch::TAG_BUFFER_BYTES_SIZE
parameter in batch parameters block when creating a batch, default is
16Mb, hard limit - 256Mb. Ywo such buffers will be available - one
for messages data, other - for blobs.
Well, in theory OOM can take place later, but that is abnormal case.
Alternatively, I could also work with an IBatch method that told me
the minimum number of guaranteed calls to IBatch::add (for a given
message buffer size). Other suggestions are welcome.
Divide what you've requested in TAG_BUFFER_BYTES_SIZE by
getAlignedLength() of your message. But be aware that this will not
work when/if we move to variable message size and string field with
unrestricted length.
And this is where the problem lies. We need a long term strategy.
One possible strategy would be to choose a number (e.g. 100), multiply
it by getAlignedLength() and then set TAG_BUFFER_BYTES_SIZE to either
the assumed default (16MB) or a larger value if 100*
getAlignedLength() > 16MB.
The problem is that, as you note, this will fail "when/if we move to
variable message size". Perhaps a getMaxAlignedLength() is needed, or
a TAG to force fixed alignment?
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