Query cache. More...

#include <QueryCache.h>

Collaboration diagram for Hypertable::QueryCache:

Classes
class	Key
	Hash key to query cache. More...

struct	KeyHash

class	QueryCacheEntry
	Internal cache entry. More...

class	RowKey
	Row key information. More...

struct	RowKeyHash

Public Member Functions
	QueryCache (uint64_t max_memory)
	Constructor. More...

bool	insert (Key key, const char tablename, const char *row, std::set< uint8_t > &columns, uint32_t cell_count, boost::shared_array< uint8_t > &result, uint32_t result_length)
	Inserts a query result. More...

bool	lookup (Key key, boost::shared_array< uint8_t > &result, uint32_t lenp, uint32_t *cell_count)
	Lookup. More...

void	invalidate (const char tablename, const char row, std::set< uint8_t > &columns)
	Invalidates cache entries. More...

uint64_t	available_memory ()
	Gets available memory. More...

uint64_t	memory_used ()
	Gets memory used. More...

void	get_stats (uint64_t max_memoryp, uint64_t available_memoryp, uint64_t total_lookupsp, uint64_t total_hitsp, int32_t *total_waiters)
	Gets cache statistics. More...

void	dump_keys (std::ofstream &out)
	Dumps keys to output file. More...

Private Types
typedef boost::multi_index_container < QueryCacheEntry, indexed_by < sequenced<>, hashed_unique < const_mem_fun < QueryCacheEntry, Key,&QueryCacheEntry::lookup_key > , KeyHash >, hashed_non_unique < const_mem_fun < QueryCacheEntry, RowKey,&QueryCacheEntry::invalidate_key > , RowKeyHash > > >	Cache

typedef Cache::nth_index< 0 >::type	Sequence

typedef Cache::nth_index< 1 >::type	LookupHashIndex

typedef Cache::nth_index< 2 >::type	InvalidateHashIndex

Private Attributes
MutexWithStatistics	m_mutex
	Mutex to serialize member access More...

Cache	m_cache
	Internal cache data structure. More...

uint64_t	m_max_memory {}
	Maximum memory to be used by cache. More...

uint64_t	m_avail_memory {}
	Available memory. More...

uint64_t	m_total_lookup_count {}
	Total lookup count. More...

uint64_t	m_total_hit_count {}
	Total hit count. More...

uint32_t	m_recent_hit_count {}
	Recent hit count (for logging) More...

Detailed Description

Query cache.

Definition at line 47 of file QueryCache.h.

Member Typedef Documentation

typedef boost::multi_index_container< QueryCacheEntry, indexed_by< sequenced<>, hashed_unique<const_mem_fun<QueryCacheEntry, Key, &QueryCacheEntry::lookup_key>, KeyHash>, hashed_non_unique<const_mem_fun<QueryCacheEntry, RowKey, &QueryCacheEntry::invalidate_key>, RowKeyHash> > > Hypertable::QueryCache::Cache

private

Definition at line 223 of file QueryCache.h.

typedef Cache::nth_index<2>::type Hypertable::QueryCache::InvalidateHashIndex

private

Definition at line 227 of file QueryCache.h.

typedef Cache::nth_index<1>::type Hypertable::QueryCache::LookupHashIndex

private

Definition at line 226 of file QueryCache.h.

typedef Cache::nth_index<0>::type Hypertable::QueryCache::Sequence

private

Definition at line 225 of file QueryCache.h.

Constructor & Destructor Documentation

QueryCache::QueryCache ( uint64_t max_memory )

Constructor.

Initializes m_max_memory and m_avail_memory to max_memory.

Parameters

max_memory Maximum amount of memory to be used by the cache

Definition at line 40 of file QueryCache.cc.

Member Function Documentation

uint64_t Hypertable::QueryCache::available_memory ( )

inline

Gets available memory.

Returns m_avail_memory

Returns: Available memory

Definition at line 152 of file QueryCache.h.

void QueryCache::dump_keys ( std::ofstream & out )

Dumps keys to output file.

Parameters

out	Output file to dump keys to

Definition at line 137 of file QueryCache.cc.

void QueryCache::get_stats	(	uint64_t *	max_memoryp,
		uint64_t *	available_memoryp,
		uint64_t *	total_lookupsp,
		uint64_t *	total_hitsp,
		int32_t *	total_waiters
	)

Gets cache statistics.

Parameters

max_memoryp	Address of variable to hold max memory.
available_memoryp	Address of variable to hold available memory.
total_lookupsp	Address of variable to hold total lookups.
total_hitsp	Address of variable to hold total hits.
total_waiters	Address of variable to hold number of threads waiting on the mutex

Definition at line 125 of file QueryCache.cc.

bool QueryCache::insert	(	Key *	key,
		const char *	tablename,
		const char *	row,
		std::set< uint8_t > &	columns,
		uint32_t	cell_count,
		boost::shared_array< uint8_t > &	result,
		uint32_t	result_length
	)

Inserts a query result.

If the size of the entry is greater than m_max_memory, then the function returns without modifying the cache. Then the old entry is removed, if there was one. Then room is created in the cache for the new entry by removing the oldest entries until enough space is available. Finally, a new cache entry is created and inserted into the cache. This function also maintains the m_avail_memory value which represents how much room is available in the cache. It is computed as m_max_memory minus an approximation of how much space is taken up by the existing cache entries.

Parameters

key	Hash key for entry to be inserted
tablename	Table name for entry to be inserted (must remain valid for lifetime of cache entry)
row	Row of entry to be inserted (must remain valid for lifetime of cache entry)
columns	Set of column IDs from scan specification used to create entry to be inserted
cell_count	Count of cells in entry to be inserted
result	Query result
result_length	Length of query result

Returns: true if result was inserted, false otherwise.

Definition at line 47 of file QueryCache.cc.

void QueryCache::invalidate	(	const char *	tablename,
		const char *	row,
		std::set< uint8_t > &	columns
	)

Invalidates cache entries.

Creates a RowKey object from tablename and row and finds all matching entires in the cache. For each matching cache entry whose columns intersect with columns, the entry is invalidated. The entry is also invalidated if either columns is empty or the cache entries columns are empty.

Parameters

tablename	Table of entries to invalidate
row	Row entries to invalidate
columns	Columns of entries to invalidate

HT_ASSERT(strcmp((*p.first).row_key.tablename, tablename) == 0 && strcmp((*p.first).row_key.row.c_str(), row) == 0);

Definition at line 162 of file QueryCache.cc.

bool QueryCache::lookup	(	Key *	key,
		boost::shared_array< uint8_t > &	result,
		uint32_t *	lenp,
		uint32_t *	cell_count
	)

Lookup.

Looks up the entry with key key, and if found, returns the query result and associated information in result, lenp, and cell_count. Also, if a cache entry is found, it is removed and re-inserted for LRU ordering.

Parameters

key	Hash key
result	Reference to shared array to hold result
lenp	Pointer to variable to hold result length
cell_count	Pointer to variable to hold count of cells in result

Returns: true if an entry was found, false otherwise

Definition at line 91 of file QueryCache.cc.

uint64_t Hypertable::QueryCache::memory_used ( )

inline

Gets memory used.

Memory used is calculated as m_max_memory minus m_avail_memory.

Returns: Memory used

Definition at line 160 of file QueryCache.h.

Member Data Documentation

uint64_t Hypertable::QueryCache::m_avail_memory {}

private

Available memory.

Definition at line 239 of file QueryCache.h.

Cache Hypertable::QueryCache::m_cache

private

Internal cache data structure.

Definition at line 233 of file QueryCache.h.

uint64_t Hypertable::QueryCache::m_max_memory {}

private

Maximum memory to be used by cache.

Definition at line 236 of file QueryCache.h.

MutexWithStatistics Hypertable::QueryCache::m_mutex

private

Mutex to serialize member access

Definition at line 230 of file QueryCache.h.

uint32_t Hypertable::QueryCache::m_recent_hit_count {}

private

Recent hit count (for logging)

Definition at line 248 of file QueryCache.h.

uint64_t Hypertable::QueryCache::m_total_hit_count {}

private

Total hit count.

Definition at line 245 of file QueryCache.h.

uint64_t Hypertable::QueryCache::m_total_lookup_count {}

private

Total lookup count.

Definition at line 242 of file QueryCache.h.

The documentation for this class was generated from the following files:

/home/doug/src/hypertable/src/cc/Hypertable/RangeServer/QueryCache.h
/home/doug/src/hypertable/src/cc/Hypertable/RangeServer/QueryCache.cc

Classes

Public Member Functions

Private Types

Private Attributes

Detailed Description

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation