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better document max_write_buffer_number_to_maintain

Browse Source 
Test Plan: compile

Reviewers: igor, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D39285
This commit is contained in:
agiardullo 2015-06-02 21:24:19 -07:00
parent 0483dab2ab
commit ca8b85ac04
2 changed files with 15 additions and 5 deletions
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6
include/rocksdb/options.h
View File

@ -250,7 +250,11 @@ struct ColumnFamilyOptions {
// after they are flushed.
// If this value is set to -1, 'max_write_buffer_number' will be used.
//
// Default: 0
// Default:
// If using an OptimisticTransactionDB, the default value will be set to the
// value
// of 'max_write_buffer_number' if it is not explicitly set by the user.
// Otherwise, the default is 0.
int max_write_buffer_number_to_maintain;
// Compress blocks using the specified compression algorithm. This

14
utilities/transactions/optimistic_transaction_impl.cc
View File

@ -292,12 +292,14 @@ Status OptimisticTransactionImpl::CheckTransactionForConflicts(DB* db) {
// Since it would be too slow to check the SST files, we will only use
// the memtables to check whether there have been any recent writes
// to this key after it was accessed in this transaction. But if the
// memtables have been flushed recently, we cannot rely on them to tell
// whether there have been any recent writes and must fail this
// Memtables do not contain a long enough history, we must fail the
// transaction.
if (earliest_seq == kMaxSequenceNumber) {
// The age of this memtable is unknown. Cannot rely on it to check
// for recent writes.
// for recent writes. This error shouldn't happen often in practice as
// the
// Memtable should have a valid earliest sequence number except in some
// corner cases (such as error cases during recovery).
result = Status::Busy(
"Could not commit transaction with as the MemTable does not "
"countain a long enough history to check write at SequenceNumber: ",
@ -311,7 +313,11 @@ Status OptimisticTransactionImpl::CheckTransactionForConflicts(DB* db) {
msg, sizeof(msg),
"Could not commit transaction with write at SequenceNumber %" PRIu64
" as the MemTable only contains changes newer than SequenceNumber "
"%" PRIu64 ".",
"%" PRIu64
". Increasing the value of the "
"max_write_buffer_number_to_maintain option could reduce the "
"frequency "
"of this error.",
key_seq, earliest_seq);
result = Status::Busy(msg);
} else {