mariadb/locktree/concurrent_tree.h

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
#ident "$Id$"
#ident "Copyright (c) 2007-2012 Tokutek Inc.  All rights reserved."
#ident "The technology is licensed by the Massachusetts Institute of Technology, Rutgers State University of New Jersey, and the Research Foundation of State University of New York at Stony Brook under United States of America Serial No. 11/760379 and to the patents and/or patent applications resulting from it."

#ifndef CONCURRENT_TREE_H
#define CONCURRENT_TREE_H

#include <ft/comparator.h>

#include "treenode.h"
#include "keyrange.h"

namespace toku {

// A concurrent_tree stores non-overlapping ranges.
// Access to disjoint parts of the tree usually occurs concurrently.

class concurrent_tree {
public:

    // A locked_keyrange gives you exclusive access to read and write
    // operations that occur on any keys in that range. You only have
    // the right to operate on keys in that range or keys that were read
    // from the keyrange using iterate()
    //
    // Access model:
    // - user prepares a locked keyrange. all threads serialize behind prepare().
    // - user breaks the serialzation point by acquiring a range, or releasing.
    // - one thread operates on a certain locked_keyrange object at a time.
    // - when the thread is finished, it releases

    class locked_keyrange {
    public:
        // effect: prepare to acquire a locked keyrange over the given
        //         concurrent_tree, preventing other threads from preparing
        //         until this thread either does acquire() or release().
        // rationale: this provides the user with a serialization point
        //            for descending / modifying the the tree.
        // There are two valid sequences of calls:
        //  - prepare, acquire, release
        //  - prepare, release
        void prepare(concurrent_tree *tree);

        // requires: the locked keyrange was prepare()'d
        // effect: acquire a locked keyrange over the given concurrent_tree.
        //         the locked keyrange represents the range of keys overlapped
        //         by the given range
        void acquire(const keyrange &range);

        // effect: releases a locked keyrange and the mutex it holds
        void release(void);

        // effect: iterate over each range this locked_keyrange represents,
        //         calling function->fn() on each node's keyrange and txnid
        //         until there are no more or the function returns false
        template <class F>
        void iterate(F *function) const;

        // inserts the given range into the tree, with an associated txnid.
        // requires: range does not overlap with anything in this locked_keyrange
        // rationale: caller is responsible for only inserting unique ranges
        void insert(const keyrange &range, TXNID txnid);

        // effect: removes the given range from the tree
        // requires: range exists exactly in this locked_keyrange
        // rationale: caller is responsible for only removing existing ranges
        void remove(const keyrange &range);

        // effect: removes everything within this locked keyrange
        // requires: the locked keyrange is over -inf, +inf
        // returns: the number of nodes removed
        // returns: *mem_released updated to the cumulative size of all keyranges destroyed
        // rationale: we'd like a fast O(n) way of removing everything from the tree
        uint64_t remove_all(uint64_t *mem_released);

    private:
        // the concurrent tree this locked keyrange is for
        concurrent_tree *m_tree;

        // the range of keys this locked keyrange represents
        keyrange m_range;

        // the subtree under which all overlapping ranges exist
        treenode *m_subtree;

        friend class concurrent_tree_unit_test;
    };

    // effect: initialize the tree to an empty state
    void create(comparator *cmp);

    // effect: destroy the tree.
    // requires: tree is empty
    void destroy(void);

    // returns: true iff the tree is empty
    bool is_empty(void);

    // returns: the memory overhead of a single insertion into the tree
    static uint64_t get_insertion_memory_overhead(void);

private:
    // the root needs to always exist so there's a lock to grab
    // even if the tree is empty. that's why we store a treenode
    // here and not a pointer to one.
    treenode m_root;

    friend class concurrent_tree_unit_test;
};

// include the implementation here so we can use templated member
// functions in locked_keyrange, which are expanded and defined in the
// compilation unit that includes "concurrent_tree.h". if we didn't
// include the source here, then there would be problems with multiple
// definitions of the tree functions
#include "concurrent_tree.cc"

} /* namespace toku */

#endif /* CONCURRENT_TREE_H */