From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 30 Apr 2019 20:37:24 +0300 From: Vladimir Davydov Subject: Re: [PATCH v3 7/7] Add merger for tuple streams (Lua part) Message-ID: <20190430173724.fgvtexkhbdutrt5x@esperanza> References: <9af4b8f1311537ef696d71a1b09bc1721bde8ef0.1554906327.git.alexander.turenko@tarantool.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9af4b8f1311537ef696d71a1b09bc1721bde8ef0.1554906327.git.alexander.turenko@tarantool.org> To: Alexander Turenko Cc: tarantool-patches@freelists.org List-ID: On Wed, Apr 10, 2019 at 06:21:25PM +0300, Alexander Turenko wrote: > A merger is a special kind of a source, which is created from a key_def > object and a set of sources. It performs a kind of the merge sort: > chooses a source with a minimal / maximal tuple on each step, consumes > a tuple from this source and repeats. The API to create a merger is the > following: > > ```lua > local ctx = merger.context.new(key_def.new(<...>)) Discussed verbally, agreed that a performance gain from using merger.context is somewhat dubious. It's compelling to drop it altogether and pass key_def to merger.new directly, creating a format every time (we can reuse formats if necessary in future). Alexander will think about it. Other than that the API and the patch looks good to me. See a few minor comments below. > local sources = {<...>} > local merger_inst = merger.new(ctx, sources, { > -- Ascending (false) or descending (true) order. > -- Default is ascending. > reverse = or , > }) > ``` > diff --git a/src/box/lua/merger.c b/src/box/lua/merger.c > new file mode 100644 > index 000000000..ebe60bc8d > --- /dev/null > +++ b/src/box/lua/merger.c > @@ -0,0 +1,1184 @@ > +static uint32_t merger_source_type_id = 0; > +static uint32_t merger_context_type_id = 0; > +static uint32_t ibuf_type_id = 0; We typically use upper case for naming variables storing Lua type ids, e.g. CTID_STRUCT_TUPLE_REF. > +static int > +lbox_merger_source_gc(struct lua_State *L) > +{ > + struct merger_source *source; > + if ((source = luaT_check_merger_source(L, 1)) == NULL) > + return 0; Is it actually possible? > + merger_source_unref(source); > + return 0; > +} > +static struct merger_source ** > +luaT_merger_new_parse_sources(struct lua_State *L, int idx, > + uint32_t *sources_count_ptr) > +{ > + /* Allocate sources array. */ > + uint32_t sources_count = lua_objlen(L, idx); > + const ssize_t sources_size = > + sources_count * sizeof(struct merger_source *); > + struct merger_source **sources = > + (struct merger_source **) malloc(sources_size); Pointless type conversion. > + if (sources == NULL) { > + diag_set(OutOfMemory, sources_size, "malloc", "sources"); > + return NULL; > + } > + > + /* Save all sources. */ > + for (uint32_t i = 0; i < sources_count; ++i) { > + lua_pushinteger(L, i + 1); > + lua_gettable(L, idx); > + > + /* Extract a source from a Lua stack. */ > + struct merger_source *source = luaT_check_merger_source(L, -1); > + if (source == NULL) { > + free(sources); > + diag_set(IllegalParams, > + "Unknown source type at index %d", i + 1); > + return NULL; > + } > + sources[i] = source; > + } > + lua_pop(L, sources_count); > + > + *sources_count_ptr = sources_count; source_count > +struct merger_source_buffer { > + struct merger_source base; > + /* > + * A reference to a Lua iterator to fetch a next chunk of > + * tuples. > + */ > + struct luaL_iterator *fetch_it; > + /* > + * A reference a buffer with a current chunk of tuples. A reference to a buffer storing the current chunk of tuples. > + * It is needed to prevent LuaJIT from collecting the > + * buffer while the source consider it as the current > + * one. > + */ > + int ref; > + /* > + * A buffer with a current chunk of tuples. > + */ > + struct ibuf *buf; > + /* > + * A merger stops before end of a buffer when it is not > + * the last merger in the chain. > + */ > + size_t remaining_tuples_cnt; Please rename to remaining_tuple_count. > +static int > +luaL_merger_source_buffer_fetch(struct merger_source_buffer *source) > +{ > + struct lua_State *L = fiber()->storage.lua.stack; > + int nresult = luaL_iterator_next(L, source->fetch_it); > + > + /* Handle a Lua error in a gen function. */ > + if (nresult == -1) > + return -1; > + > + /* No more data: do nothing. */ > + if (nresult == 0) > + return 0; > + > + /* Handle incorrect results count. */ > + if (nresult != 2) { > + diag_set(IllegalParams, "Expected , , got %d " > + "return values", nresult); > + return -1; > + } > + > + /* Set a new buffer as the current chunk. */ > + if (source->ref > 0) > + luaL_unref(L, LUA_REGISTRYINDEX, source->ref); > + lua_pushvalue(L, -nresult + 1); /* Popped by luaL_ref(). */ > + source->ref = luaL_ref(L, LUA_REGISTRYINDEX); > + source->buf = luaT_check_ibuf(L, -1); > + assert(source->buf != NULL); | tarantool> m = merger.new(c, {merger.new_buffer_source(box.space._space:pairs())}) | --- | ... | | tarantool> m:select() | luaL_merger_source_buffer_fetch: Assertion `source->buf != NULL' failed. Please fail gracefully in this case. > + lua_pop(L, nresult); > + > + /* Update remaining_tuples_cnt and skip the header. */ > + if (decode_header(source->buf, &source->remaining_tuples_cnt) != 0) { > + diag_set(IllegalParams, "Invalid merger source %p", > + &source->base); > + return -1; > + } > + return 1; > +} > + > +/* Virtual methods */ > + > +static void > +luaL_merger_source_buffer_delete(struct merger_source *base) > +{ > + struct merger_source_buffer *source = container_of(base, > + struct merger_source_buffer, base); > + > + assert(source->fetch_it != NULL); > + luaL_iterator_delete(source->fetch_it); > + if (source->ref > 0) > + luaL_unref(tarantool_L, LUA_REGISTRYINDEX, source->ref); > + > + free(source); > +} > + > +static int > +luaL_merger_source_buffer_next(struct merger_source *base, > + box_tuple_format_t *format, > + struct tuple **out) > +{ > + struct merger_source_buffer *source = container_of(base, > + struct merger_source_buffer, base); > + > + /* > + * Handle the case when all data were processed: ask a > + * next chunk until a non-empty chunk is received or a > + * chunks iterator ends. > + */ > + while (source->remaining_tuples_cnt == 0) { > + int rc = luaL_merger_source_buffer_fetch(source); > + if (rc < 0) > + return -1; > + if (rc == 0) { > + *out = NULL; > + return 0; > + } > + } > + if (ibuf_used(source->buf) == 0) { > + diag_set(IllegalParams, "Unexpected msgpack buffer end"); > + return -1; > + } > + const char *tuple_beg = source->buf->rpos; > + const char *tuple_end = tuple_beg; > + /* > + * mp_next() is faster then mp_check(), but can read bytes > + * outside of the buffer and so can cause segmentation > + * faults or an incorrect result. > + * > + * We check buffer boundaries after the mp_next() call and > + * throw an error when the boundaries are violated, but it > + * does not save us from possible segmentation faults. > + * > + * It is in a user responsibility to provide valid > + * msgpack. Ugh, I'd check the buffer with mp_check anyway. Would probably provide an option to skip the check if required ('unchecked'). Not sure if it's really necessary though. > + */ > + mp_next(&tuple_end); > + --source->remaining_tuples_cnt; > + if (tuple_end > source->buf->wpos) { > + diag_set(IllegalParams, "Unexpected msgpack buffer end"); > + return -1; > + } > + source->buf->rpos = (char *) tuple_end; > + if (format == NULL) > + format = box_tuple_format_default(); I'd pass tuple_format_runtime explicitly to the ->next callback. Special-casing NULL is kinda ugly. > + struct tuple *tuple = box_tuple_new(format, tuple_beg, tuple_end); > + if (tuple == NULL) > + return -1; > + > + box_tuple_ref(tuple); > + *out = tuple; > + return 0; > +} > +static int > +encode_result_buffer(struct lua_State *L, struct merger_source *source, > + struct ibuf *obuf, uint32_t limit) Better rename 'obuf' to 'out' or 'buf' or something - we have struct obuf so 'struct ibuf *obuf' looks misleading. > +{ > + uint32_t result_len = 0; > + uint32_t result_len_offset = 4; > + > + /* > + * Reserve maximum size for the array around resulting > + * tuples to set it later. > + */ > + encode_header(obuf, UINT32_MAX); > + > + /* Fetch, merge and copy tuples to the buffer. */ > + struct tuple *tuple; > + int rc = 0; > + while (result_len < limit && (rc = > + source->vtab->next(source, NULL, &tuple)) == 0 && > + tuple != NULL) { > + uint32_t bsize = tuple->bsize; > + ibuf_reserve(obuf, bsize); > + memcpy(obuf->wpos, tuple_data(tuple), bsize); > + obuf->wpos += bsize; > + result_len_offset += bsize; > + ++result_len; > + > + /* The received tuple is not more needed. */ > + box_tuple_unref(tuple); > + } > + > + if (rc != 0) > + return luaT_error(L); > + > + /* Write the real array size. */ > + mp_store_u32(obuf->wpos - result_len_offset, result_len); > + > + return 0; > +} > +static int > +lbox_merger_source_select(struct lua_State *L) > +{ > + struct merger_source *source; > + int top = lua_gettop(L); > + bool ok = (top == 1 || top == 2) && > + /* Merger source. */ > + (source = luaT_check_merger_source(L, 1)) != NULL && > + /* Opts. */ > + (lua_isnoneornil(L, 2) == 1 || lua_istable(L, 2) == 1); > + if (!ok) > + return lbox_merger_source_select_usage(L, NULL); > + > + uint32_t limit = 0xFFFFFFFF; Hmm, UINT32_MAX?