Assertion `!should_flush_' failed. from memtable

[honglianglu]

I have met difficulties for using the rocksdb. And when I tried to use a Hashskiplistrep, I can not open the db. And the docs is found helpless.
I set the options as:

rocksdb::Options opt = rocksdb::Options();
opt.IncreaseParallelism(2);
opt.create_if_missing = true;
opt.max_open_files = 300000;
auto prefix_extractor = NewFixedPrefixTransform(8);
opt.prefix_extractor.reset(prefix_extractor);
opt.memtable_factory.reset(NewHashSkipListRepFactory(bucket_count, skiplist_height, skiplist_branching_factor));
opt.table_factory.reset(NewPlainTableFactory());
rocksdb::Status s = rocksdb::DB::Open(opt, DBPath, &db);

when run with this , the error come as:

db/memtable.cc:55: rocksdb::MemTable::MemTable(const rocksdb::InternalKeyComparator&, const rocksdb::Options&): Assertion `!should_flush_' failed.

I am using the latest version of the RocksDB on ubuntu 14.04.
Could any one help me? Thanks a lot!

[igorcanadi]

Can you try increasing write_buffer_size? I think the problem is that you configured memtable in such a way that even the empty memtable exceeds the memory limit (write_buffer_size) and needs to be flushed. What's your bucket_count?

[honglianglu]

@igorcanadi Yes, thank you! And when I set the write_buffer_size to be 64M, the problem gone. and the bucket_count is set to be 1000. But I meet another problem, saying that:

util/env_posix.cc:235: rocksdb::{anonymous}::PosixRandomAccessFile::PosixRandomAccessFile(const string&, int, const rocksdb::EnvOptions&): Assertion `!options.use_mmap_reads' failed.

I found that the Envoptions can set use_mmap_reads to be true, but how can I make it take effect in the Env? I found no way to set a EnvOptions for Env variable.
Thanks a lot!

[igorcanadi]

Are you running on 32-bit system?

[igorcanadi]

This should fix it https://reviews.facebook.net/D22419

[honglianglu]

@igorcanadi Yes, I am running on a 32-bit system. But I am sorry to cannot follow you. How can the https://reviews.facebook.net/D22419 solve my problem? Could you please make a explain on that? Thank you very much!

[igorcanadi]

Once it lands, you won't get any more assertions

[igorcanadi]

@honglianglu does it work now?

[honglianglu]

@igorcanadi thank you, it work now. as you have posted
" We're initializing PosixRandomAccessFile when use_mmap_reads is true OR when we're on 32-bit system, see: https://github.com/facebook/rocksdb/blob/master/util/env_posix.cc#L1075

Therefore, when we're on 32-bit system and use_mmap_reads is false, we will hit the assertion."

I have got about that, and I deleted the table_factory. Thanks a lot!
Then the document on how to use prefix hash should be updated,right?

[igorcanadi]

Why would the document need to be updated?

[honglianglu]

2014-03-27-RocksDB-Meetup-Siying-Prefix-Hash.pdf is useless!

[igorcanadi]

Are you saying it's useless on 32-bit system?

[igorcanadi]

Sorry, use_mmap_reads needs to be false. That is the default anyway.