@ -38,83 +38,9 @@ class Slice;
struct BlockBasedTableOptions ;
struct ConfigOptions ;
// A class that takes a bunch of keys, then generates filter
class FilterBitsBuilder {
public :
virtual ~ FilterBitsBuilder ( ) { }
// Add a key (or prefix) to the filter. Typically, a builder will keep
// a set of 64-bit key hashes and only build the filter in Finish
// when the final number of keys is known. Keys are added in sorted order
// and duplicated keys are possible, so typically, the builder will
// only add this key if its hash is different from the most recently
// added.
virtual void AddKey ( const Slice & key ) = 0 ;
// Called by RocksDB before Finish to populate
// TableProperties::num_filter_entries, so should represent the
// number of unique keys (and/or prefixes) added, but does not have
// to be exact. `return 0;` may be used to conspicuously indicate "unknown".
virtual size_t EstimateEntriesAdded ( ) = 0 ;
// Generate the filter using the keys that are added
// The return value of this function would be the filter bits,
// The ownership of actual data is set to buf
virtual Slice Finish ( std : : unique_ptr < const char [ ] > * buf ) = 0 ;
// Similar to Finish(std::unique_ptr<const char[]>* buf), except that
// for a non-null status pointer argument, it will point to
// Status::Corruption() when there is any corruption during filter
// construction or Status::OK() otherwise.
//
// WARNING: do not use a filter resulted from a corrupted construction
virtual Slice Finish ( std : : unique_ptr < const char [ ] > * buf ,
Status * /* status */ ) {
return Finish ( buf ) ;
}
// Verify the filter returned from calling FilterBitsBuilder::Finish.
// The function returns Status::Corruption() if there is any corruption in the
// constructed filter or Status::OK() otherwise.
//
// Implementations should normally consult
// FilterBuildingContext::table_options.detect_filter_construct_corruption
// to determine whether to perform verification or to skip by returning
// Status::OK(). The decision is left to the FilterBitsBuilder so that
// verification prerequisites before PostVerify can be skipped when not
// configured.
//
// RocksDB internal will always call MaybePostVerify() on the filter after
// it is returned from calling FilterBitsBuilder::Finish
// except for FilterBitsBuilder::Finish resulting a corruption
// status, which indicates the filter is already in a corrupted state and
// there is no need to post-verify
virtual Status MaybePostVerify ( const Slice & /* filter_content */ ) {
return Status : : OK ( ) ;
}
// Approximate the number of keys that can be added and generate a filter
// <= the specified number of bytes. Callers (including RocksDB) should
// only use this result for optimizing performance and not as a guarantee.
virtual size_t ApproximateNumEntries ( size_t bytes ) = 0 ;
} ;
// A class that checks if a key can be in filter
// It should be initialized by Slice generated by BitsBuilder
class FilterBitsReader {
public :
virtual ~ FilterBitsReader ( ) { }
// Check if the entry match the bits in filter
virtual bool MayMatch ( const Slice & entry ) = 0 ;
// Check if an array of entries match the bits in filter
virtual void MayMatch ( int num_keys , Slice * * keys , bool * may_match ) {
for ( int i = 0 ; i < num_keys ; + + i ) {
may_match [ i ] = MayMatch ( * keys [ i ] ) ;
}
}
} ;
// As of RocksDB 7.0, the details of these classes are internal
class FilterBitsBuilder ;
class FilterBitsReader ;
// Contextual information passed to BloomFilterPolicy at filter building time.
// Used in overriding FilterPolicy::GetBuilderWithContext(). References other
@ -154,20 +80,11 @@ struct FilterBuildingContext {
TableFileCreationReason reason = TableFileCreationReason : : kMisc ;
} ;
// We add a new format of filter block called full filter block
// This new interface gives you more space of customization
//
// For the full filter block, you can plug in your version by implement
// the FilterBitsBuilder and FilterBitsReader
//
// There are two sets of interface in FilterPolicy
// Set 1: CreateFilter, KeyMayMatch: used for blockbased filter
// Set 2: GetFilterBitsBuilder, GetFilterBitsReader, they are used for
// full filter.
// Set 1 MUST be implemented correctly, Set 2 is optional
// RocksDB would first try using functions in Set 2. if they return nullptr,
// it would use Set 1 instead.
// You can choose filter type in NewBloomFilterPolicy
// Determines what kind of filter (if any) to generate in SST files, and under
// which conditions. API users can create custom filter policies that
// defer to other built-in policies (see NewBloomFilterPolicy and
// NewRibbonFilterPolicy) based on the context provided to
// GetBuilderWithContext.
class FilterPolicy {
public :
virtual ~ FilterPolicy ( ) ;
@ -177,9 +94,9 @@ class FilterPolicy {
// policy string.
// The value describes the FilterPolicy being created.
// For BloomFilters, value may be a ":"-delimited value of the form:
// "bloomfilter:[bits_per_key]:[use_block_based_builder] ",
// e.g. ""bloomfilter:4:true "
// The above string is equivalent to calling NewBloomFilterPolicy(4, true ).
// "bloomfilter:[bits_per_key]",
// e.g. ""bloomfilter:4"
// The above string is equivalent to calling NewBloomFilterPolicy(4).
static Status CreateFromString ( const ConfigOptions & config_options ,
const std : : string & value ,
std : : shared_ptr < const FilterPolicy > * result ) ;
@ -191,20 +108,20 @@ class FilterPolicy {
virtual const char * Name ( ) const = 0 ;
// Return a new FilterBitsBuilder for constructing full or partitioned
// filter blocks. The configuration details can depend on the input
// FilterBuildingContext but must be serialized such that FilterBitsReader
// can operate based on the block contents without knowing a
// FilterBuildingContext.
// Change in 7.0 release: returning nullptr indicates "no filter"
// filter blocks, or return nullptr to indicate "no filter". Custom
// implementations should defer to a built-in FilterPolicy to get a
// new FilterBitsBuilder, but the FilterBuildingContext can be used
// to decide which built-in FilterPolicy to defer to.
virtual FilterBitsBuilder * GetBuilderWithContext (
const FilterBuildingContext & ) const = 0 ;
// Return a new FilterBitsReader for full or partitioned filter blocks.
// Caller retains ownership of any buffer pointed to by the input Slice.
// Custom implementation should defer to GetFilterBitsReader on any
// built-in FilterPolicy, which can read filters generated by any other
// built-in FilterPolicy.
virtual FilterBitsReader * GetFilterBitsReader (
const Slice & /*contents*/ ) const {
return nullptr ;
}
const Slice & /*contents*/ ) const = 0 ;
} ;
// Return a new filter policy that uses a bloom filter with approximately
Peter Dillinger
3 years ago
committed by