[RocksDB] Test diff on performance branch

Summary: trivia comment change

Test Plan: Go through the step ofs developing under the performance branch

Reviewers: dhruba, kailiu, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14259
MergingIterator.Seek() to lazily initialize MinHeap

Summary:
For the use cases that prefix filtering is enabled, initializing heaps when doing MergingIterator.Seek() might introduce non-negligible costs. This patch makes it lazily done.

Test Plan: make all check

Reviewers: haobo,dhruba,kailiu

CC:

Task ID: #

Blame Rev:
Inline a couple of functions and put one save lazily clearing

Summary:
Machine several functions inline.
Also, in DBIter.Seek() make value cleaning up lazily done.
These are for the use case that Seek() are called lots of times but few return values.

Test Plan: make all check

Differential Revision: https://reviews.facebook.net/D14217
A Simple Plain Table

Summary:
A Simple plain table format. No block structure. When creating the table reader, scanning the full table to create indexes.

Test Plan:Add unit test

Reviewers:haobo,dhruba,kailiu

CC:

Task ID: #

Blame Rev:
Fix a memory leak happened in table_test
[Only for Performance Branch] A Hacky patch to lazily generate memtable key for prefix-hashed memtables.

Summary:
For prefix mem tables, encoding mem table key may be unnecessary if the prefix doesn't have any key. This patch is a little bit hacky but I want to try out the performance gain of removing this lazy initialization.

In longer term, we might want to revisit the way we abstract mem tables implementations.

Test Plan: make all check

Reviewers: haobo, igor, kailiu

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14265
Allow users to profile a query and see bottleneck of the query

Summary:
Provide a framework to profile a query in detail to figure out latency bottleneck. Currently, in Get(), Put() and iterators, 2-3 simple timing is used. We can easily add more profile counters to the framework later.

Test Plan: Enable this profiling in seveal existing tests.

Reviewers: haobo, dhruba, kailiu, emayanke, vamsi, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14001

Conflicts:
	table/merger.cc
Add BloomFilter to PlainTableIterator::Seek()

Summary:
This patch adds a simple bloom filter in PlainTableIterator::Seek()

Test Plan: N/A

Reviewers:

CC:

Task ID: #

Blame Rev:
[For Performance Branch] Bloom filter in PlainTableIterator::Seek() - Update 1

Summary:
Address @haobo's comments in D14277

Test Plan: ./indexed_table_db_test

Reviewers: haobo

CC:

Task ID: #

Blame Rev:
[RocksDB Performance Branch] Fix a regression bug of munmap

Summary:
Fix a stupid bug I just introduced in b59d4d5a5051263b4bfcef00913219ffe4654e42, which I didn't even mean to include.
GCC might remove the munmap.

Test Plan: Run it and make sure munmap succeeds

Reviewers: haobo, kailiu

Reviewed By: kailiu

CC: dhruba, reconnect.grayhat, leveldb

Differential Revision: https://reviews.facebook.net/D14361
[RocksDB][Performance Branch] Make height and branching factor configurable for skiplist implementation

Summary: As title. Especially, HashSkipListRepFactory will be able to specify a relatively small height, to reduce the memory overhead of one skiplist per bucket.

Test Plan: make check and test it on leaf4

Reviewers: dhruba, sdong, kailiu

CC: reconnect.grayhat, leveldb

Differential Revision: https://reviews.facebook.net/D14307
Merge branch 'master' into perf
Make the default compilation debug-friendly
[RocksDB Performance Branch] A more customized index in PlainTableReader

Summary:
PlainTableReader to use a more customized hash table. This patch assumes the SST file is smaller than 2GB:
(1) Every bucket uses 32-bit integer
(2) no key is stored in bucket
(3) use the first bit of the bucket value to distinguish it points to the file offset or a second level index.
This index schema fits the use case that most of prefixes have very small number of keys

Test Plan: plain_table_db_test

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14343
Parameterize table magic number

Summary:

As we are having different types of tables and they all might share the same structure in block-based table:

[metaindex block]
[index block]
[Footer]

To be able to identify differnt types of tables, we need to parameterize the "magic number" in the `Footer`.

Test Plan:

make check
Introducing the concept of NULL block handle
Generalize footer reading from file

Summary:

Generalizing this process will help us to re-use the code for plain table

Test Plan:

ran ./table_test
Fix a bunch of mac compilation issues in performance branch
Extract metaindex block from block-based table

Summary: This change will allow other table to reuse the code for meta blocks.

Test Plan: all existing unit tests passed

Reviewers: dhruba, haobo, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14475
[RocksDB Performance Branch] Introduce MergeContext to Lazily Initialize merge operand list

Summary: In get operations, merge_operands is only used in few cases. Lazily initialize it can reduce average latency in some cases

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14415