iterator.go
iterator.go - Overview
This file defines iterators for traversing data within a table, including block-level iteration and table-level concatenation. It includes structures and functions for seeking, moving forward/backward, and accessing key-value pairs.
Detailed Documentation
blockIterator
Purpose: Iterates over entries within a block of a table.
Fields:
data:[]byte- Raw data of the block.idx:int- Index of the current entry.err:error- Any error encountered during iteration.baseKey:[]byte- Base key for the block.key:[]byte- Current key.val:[]byte- Current value.entryOffsets:[]uint32- Offsets of each entry within the block.block:*Block- Pointer to the block being iterated.tableID:uint64- ID of the table the block belongs to.blockID:int- ID of the block.prevOverlap:uint16- Overlap of the previous key with the base key.
setBlock(b *Block)
Purpose: Sets the block to iterate over, resetting the iterator's state.
Parameters:
b:*Block- The block to iterate over.
Returns: None
setIdx(i int)
Purpose: Sets the iterator to a specific index within the block and sets the key and value.
Parameters:
i:int- The index to set the iterator to.
Returns: None
Valid() bool
Purpose: Checks if the iterator is valid (no error and within bounds).
Parameters: None
Returns: bool - True if the iterator is valid, false otherwise.
Error() error
Purpose: Returns the current error of the iterator.
Parameters: None
Returns: error - The current error, or nil if no error.
Close()
Purpose: Decrements the reference count of the associated block.
Parameters: None
Returns: None
seek(key []byte, whence int)
Purpose: Moves the iterator to the first entry that is greater than or equal to the given key.
Parameters:
key:[]byte- The key to seek to.whence:int- Start index for search.
Returns: None
seekToFirst()
Purpose: Moves the iterator to the first element in the block.
Parameters: None
Returns: None
seekToLast()
Purpose: Moves the iterator to the last element in the block.
Parameters: None
Returns: None
next()
Purpose: Moves the iterator to the next element in the block.
Parameters: None
Returns: None
prev()
Purpose: Moves the iterator to the previous element in the block.
Parameters: None
Returns: None
Iterator
Purpose: An iterator for a Table.
Fields:
t:*Table- The table being iterated.bpos:int- The current block position.bi:blockIterator- The block iterator.err:error- Any error encountered during iteration.opt:int- Options for the iterator (e.g., reversed, no cache).
NewIterator(opt int) *Iterator
Purpose: Creates a new iterator for the table.
Parameters:
opt:int- Options for the iterator. Valid options areREVERSEDandNOCACHE.
Returns: *Iterator - A new iterator for the table.
Close() error
Purpose: Closes the iterator, decrementing the table's reference count.
Parameters: None
Returns: error - Any error encountered during closing.
reset()
Purpose: Resets the iterator to its initial state.
Parameters: None
Returns: None
Valid() bool
Purpose: Checks if the iterator is valid (no error).
Parameters: None
Returns: bool - True if the iterator is valid, false otherwise.
useCache() bool
Purpose: Determines whether to use the cache.
Parameters: None
Returns: bool - true if the cache should be used, false otherwise.
seekToFirst()
Purpose: Seeks to the first key in the table.
Parameters: None
Returns: None
seekToLast()
Purpose: Seeks to the last key in the table.
Parameters: None
Returns: None
seekHelper(blockIdx int, key []byte)
Purpose: Seeks to a specific key within a specific block.
Parameters:
blockIdx:int- The index of the block to seek within.key:[]byte- The key to seek to.
Returns: None
seekFrom(key []byte, whence int)
Purpose: Seeks to the first key that is greater than or equal to the given key, starting from a specific position.
Parameters:
key:[]byte- The key to seek to.whence:int- Origin of the search.
Returns: None
seek(key []byte)
Purpose: Seeks to the first key that is greater than or equal to the given key.
Parameters:
key:[]byte- The key to seek to.
Returns: None
seekForPrev(key []byte)
Purpose: Seeks to the last key that is less than or equal to the given key.
Parameters:
key:[]byte- The key to seek to.
Returns: None
next()
Purpose: Moves the iterator to the next key in the table.
Parameters: None
Returns: None
prev()
Purpose: Moves the iterator to the previous key in the table.
Parameters: None
Returns: None
Key() []byte
Purpose: Returns the current key.
Parameters: None
Returns: []byte - The current key.
Value() y.ValueStruct
Purpose: Returns the current value as a y.ValueStruct.
Parameters: None
Returns: y.ValueStruct - The current value.
ValueCopy() y.ValueStruct
Purpose: Copies the current value and returns it as a decoded y.ValueStruct.
Parameters: None
Returns: y.ValueStruct - A copy of the current value.
Next()
Purpose: Moves the iterator to the next key, respecting the iteration direction.
Parameters: None
Returns: None
Rewind()
Purpose: Resets the iterator to the beginning or end, depending on the iteration direction.
Parameters: None
Returns: None
Seek(key []byte)
Purpose: Seeks to a specific key, respecting the iteration direction.
Parameters:
key:[]byte- The key to seek to.
Returns: None
ConcatIterator
Purpose: Concatenates multiple Table iterators into a single iterator.
Fields:
idx:int- Index of the currently active iterator.cur:*Iterator- The current iterator.iters:[]*Iterator- Slice of iterators to concatenate.tables:[]*Table- Slice of tables corresponding to the iterators.options:int- Options for the iterator (e.g., reversed, no cache).
NewConcatIterator(tbls []*Table, opt int) *ConcatIterator
Purpose: Creates a new concatenated iterator.
Parameters:
tbls:[]*Table- The tables to iterate over.opt:int- Options for the iterator. Valid options areREVERSEDandNOCACHE.
Returns: *ConcatIterator - A new concatenated iterator.
setIdx(idx int)
Purpose: Sets the current iterator index.
Parameters:
idx:int- The index of the iterator to set.
Returns: None
Rewind()
Purpose: Resets the concatenated iterator to the beginning or end, depending on the iteration direction.
Parameters: None
Returns: None
Valid() bool
Purpose: Checks if the concatenated iterator is valid.
Parameters: None
Returns: bool - True if the iterator is valid, false otherwise.
Key() []byte
Purpose: Returns the current key.
Parameters: None
Returns: []byte - The current key.
Value() y.ValueStruct
Purpose: Returns the current value as a y.ValueStruct.
Parameters: None
Returns: y.ValueStruct - The current value.
Seek(key []byte)
Purpose: Seeks to a specific key within the concatenated iterators, respecting the iteration direction.
Parameters:
key:[]byte- The key to seek to.
Returns: None
Next()
Purpose: Advances the concatenated iterator to the next key.
Parameters: None
Returns: None
Close() error
Purpose: Closes the concatenated iterator and all underlying iterators, decrementing the table's reference count.
Parameters: None
Returns: error - Any error encountered during closing.