# How to rewrite fdb GetKeyValuesReply?
**URL:** https://forums.foundationdb.org/t/how-to-rewrite-fdb-getkeyvaluesreply/4342
**Category:** Development
**Created:** [January 30, 2024, 8:48am UTC](https://forums.foundationdb.org/t/how-to-rewrite-fdb-getkeyvaluesreply/4342 "2024-01-30T08:48:29Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@gripleaf](https://forums.foundationdb.org/u/gripleaf)
#### Post date: [January 30, 2024, 8:48am UTC](https://forums.foundationdb.org/t/how-to-rewrite-fdb-getkeyvaluesreply/4342/1 "2024-01-30T08:48:29Z")
For some reason, I want to rewrite the fdb GetKeyValuesReply before SS send back reply. The code modified in `storageserver.actor.cpp:getKeyValuesQ` with fdb 7.1.44:
```auto
if (!r.data.empty() && /*some conditions*/) {
GetKeyValuesReply new_r;
new_r.arena.dependsOn(r.arena);
new_r.penalty = r.penalty;
new_r.more = r.more;
new_r.version = r.version;
new_r.cached = r.cached;
new_r.error = r.error;
for (int i = 0; i < r.data.size(); i++) {
if (filterOut(r.data[i].key, r.data[i].value) && (i != 0 && i != r.data.size() -1)) {
// filter out the data item except first and last item.
continue;
}
new_r.data.push_back(new_r.arena, r.data[i]);
}
req.reply.send(new_r);
} else {
req.reply.send(r);
}
```
when I compile & run above code, it always cause core dump.
Is there something wrong that I didn’t recognize about arena or send func?
---
### Author:  [@gripleaf](https://forums.foundationdb.org/u/gripleaf)
#### Post date: [January 30, 2024, 9:30am UTC](https://forums.foundationdb.org/t/how-to-rewrite-fdb-getkeyvaluesreply/4342/2 "2024-01-30T09:30:49Z")
I try another way to build my reply, it seems work. example code like:
```auto
if (!r.data.empty() && /*some conditions*/) {
int offset = 0;
for (int i = 0; i < r.data.size(); i++) {
if (filterOut(r.data[i].key, r.data[i].value) && (i != 0 && i != r.data.size() -1)) {
continue;
}
r.data[offset] = r.data[i];
offset++;
}
while (r.data.size() > offset) { r.data.pop_back(); }
req.reply.send(r);
} else {
req.reply.send(r);
}
```
It seems I make some mistakes on arena…
When SS really call send in network level, the `new_r` memory in above code is freed, then SS access invalid memory address and core dump.
---
### Author:  [@gripleaf](https://forums.foundationdb.org/u/gripleaf)
#### Post date: [February 2, 2024, 2:48am UTC](https://forums.foundationdb.org/t/how-to-rewrite-fdb-getkeyvaluesreply/4342/3 "2024-02-02T02:48:11Z")
Is anyone can help me explain above problem, or provide some documents about arena?