lmdb::database Class Reference

Manages a LMDB environment for safe memory-map resizing. Thread-safe. More...

#include <database.h>

Public Member Functions
	database (environment env)
	database (database &&)=delete
	database (database const &)=delete
virtual	~database () noexcept
database &	operator= (database &&)=delete
database &	operator= (database const &)=delete
expect< void >	resize () noexcept
expect< read_txn >	create_read_txn (suspended_txn txn=nullptr) noexcept
expect< suspended_txn >	reset_txn (read_txn txn) noexcept
expect< write_txn >	create_write_txn () noexcept
expect< void >	commit (write_txn txn) noexcept
	Commit the read-write transaction.
template<typename F>
std::result_of< F(MDB_txn &)>::type	try_write (F f, unsigned attempts=3)

Detailed Description

Manages a LMDB environment for safe memory-map resizing. Thread-safe.

Definition at line 64 of file database.h.

Constructor & Destructor Documentation

database() [1/3]

lmdb::database::database

(

environment

env

)

Definition at line 113 of file database.cpp.

      : env(std::move(env)), ctx{{}, ATOMIC_FLAG_INIT}
    {
        if (handle())
        {
            const int err = mdb_env_set_userctx(handle(), std::addressof(ctx));
            if (err)
                ELECTRONEUM_THROW(lmdb::error(err), "Failed to set user context");
        }
    }

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database() [2/3]

lmdb::database::database ( database && )

delete

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database() [3/3]

lmdb::database::database ( database const & )

delete

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~database()

lmdb::database::~database ( )

virtualnoexcept

Definition at line 124 of file database.cpp.

    {
        while (ctx.active);
    }

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Member Function Documentation

commit()

expect< void > lmdb::database::commit ( write_txn txn )

noexcept

Commit the read-write transaction.

Definition at line 179 of file database.cpp.

    {
        ELECTRONEUM_PRECOND(txn != nullptr);
        ELECTRONEUM_LMDB_CHECK(mdb_txn_commit(txn.get()));
        txn.release();
        release_context(ctx);
        return success();
    }

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create_read_txn()

expect< read_txn > lmdb::database::create_read_txn ( suspended_txn txn = nullptr )

noexcept

Returns

A read only LMDB transaction, reusing txn if provided.

Definition at line 147 of file database.cpp.

    {
        if (txn)
        {
            acquire_context(ctx);
            const int err = mdb_txn_renew(txn.get());
            if (err)
            {
                release_context(ctx);
                return {lmdb::error(err)};
            }
            return read_txn{txn.release()};
        }
        auto new_txn = do_create_txn(MDB_RDONLY);
        if (new_txn)
            return read_txn{new_txn->release()};
        return new_txn.error();
    }

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create_write_txn()

expect< write_txn > lmdb::database::create_write_txn ( )

noexcept

Returns

A read-write LMDB transaction.

Definition at line 174 of file database.cpp.

    {
        return do_create_txn(0);
    }

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operator=() [1/2]

database & lmdb::database::operator= ( database && )

delete

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operator=() [2/2]

database & lmdb::database::operator= ( database const & )

delete

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reset_txn()

expect< suspended_txn > lmdb::database::reset_txn ( read_txn txn )

noexcept

Returns

txn after releasing context.

Definition at line 166 of file database.cpp.

    {
        ELECTRONEUM_PRECOND(txn != nullptr);
        mdb_txn_reset(txn.get());
        release_context(ctx);
        return suspended_txn{txn.release()};
    }

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resize()

expect< void > lmdb::database::resize ( )

noexcept

Resize the memory map for the LMDB environment. Will block until all reads/writes on the environment complete.

Definition at line 129 of file database.cpp.

    {
        ELECTRONEUM_PRECOND(handle() != nullptr);
 
        while (ctx.lock.test_and_set());
        while (ctx.active);
 
        MDB_envinfo info{};
        ELECTRONEUM_LMDB_CHECK(mdb_env_info(handle(), &info));
 
        const mdb_size_t resize = std::min(info.me_mapsize, max_resize);
        const int err = mdb_env_set_mapsize(handle(), info.me_mapsize + resize);
        ctx.lock.clear();
        if (err)
            return {lmdb::error(err)};
        return success();
    }

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try_write()

template<typename F>

std::result_of< F(MDB_txn &)>::type lmdb::database::try_write ( F f, unsigned attempts = 3 )

inline

Create a write transaction, pass it to f, then try to commit the write if f succeeds.

Template Parameters

F	must be callable with signature expect<T>(MDB_txn&).

Parameters

f	must be re-startable if lmdb::error(MDB_MAP_FULL).

Returns

The result of calling f.

Definition at line 113 of file database.h.

        {
            for (unsigned i = 0; i < attempts; ++i)
            {
                expect<write_txn> txn = create_write_txn();
                if (!txn)
                    return txn.error();
 
                ELECTRONEUM_PRECOND(*txn != nullptr);
                const auto wrote = f(*(*txn));
                if (wrote)
                {
                    ELECTRONEUM_CHECK(commit(std::move(*txn)));
                    return wrote;
                }
                if (wrote != lmdb::error(MDB_MAP_FULL))
                    return wrote;
 
                txn->reset();
                ELECTRONEUM_CHECK(this->resize());
            }
            return {lmdb::error(MDB_MAP_FULL)};
        }

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---

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

• /home/abuild/rpmbuild/BUILD/electroneum-5.1.3.1-build/electroneum-5.1.3.1/src/lmdb/database.h
• /home/abuild/rpmbuild/BUILD/electroneum-5.1.3.1-build/electroneum-5.1.3.1/src/lmdb/database.cpp