diff options
| -rw-r--r-- | sql/multi_range_read.cc | 105 | ||||
| -rw-r--r-- | sql/multi_range_read.h | 29 |
2 files changed, 76 insertions, 58 deletions
diff --git a/sql/multi_range_read.cc b/sql/multi_range_read.cc index 72099bb0967..fa7f627760a 100644 --- a/sql/multi_range_read.cc +++ b/sql/multi_range_read.cc @@ -282,8 +282,20 @@ scan_it_again: DBUG_RETURN(result); } +/**************************************************************************** + * Mrr_*_reader classes (building blocks for DS-MRR) + ***************************************************************************/ -/***** Mrr_*_reader classes **************************************************/ +int Mrr_simple_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, + void *seq_init_param, uint n_ranges, + uint mode, Buffer_manager *buf_manager_arg) +{ + HANDLER_BUFFER no_buffer = {NULL, NULL, NULL}; + h= h_arg; + res= 0; + return h->handler::multi_range_read_init(seq_funcs, seq_init_param, n_ranges, + mode, &no_buffer); +} int Mrr_simple_index_reader::get_next(char **range_info) { @@ -297,44 +309,35 @@ int Mrr_simple_index_reader::get_next(char **range_info) return res; } -int Mrr_simple_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, - void *seq_init_param, uint n_ranges, - uint mode, Buffer_manager *buf_manager_arg) -{ - HANDLER_BUFFER no_buffer = {NULL, NULL, NULL}; - h= h_arg; - res= 0; - return h->handler::multi_range_read_init(seq_funcs, seq_init_param, n_ranges, - mode, &no_buffer); -} /** - DS-MRR/CPK: multi_range_read_next() function - - @param range_info OUT identifier of range that the returned record belongs to + @brief Get next index record + + @param range_info OUT identifier of range that the returned record belongs to @note - This function walks over key buffer and does index reads, i.e. it produces - {current_record, range_id} pairs. - - The function has the same call contract like multi_range_read_next()'s. - We actually iterate over nested sequences: - - a disjoint sequence of index ranges - - each range has multiple records - - each record goes into multiple identical ranges. + - an ordered sequence of groups of identical keys + - each key group has key value, which has multiple matching records + - thus, each record matches all members of the key group @retval 0 OK, next record was successfully read @retval HA_ERR_END_OF_FILE End of records @retval Other Some other error */ -int Mrr_ordered_index_reader::get_next(char **range_info_arg) +int Mrr_ordered_index_reader::get_next(char **range_info) { DBUG_ENTER("Mrr_ordered_index_reader::get_next"); - if (!know_key_tuple_params) /* We're in startup phase */ + if (!know_key_tuple_params) + { + /* + We're at the very start, haven't filled the buffer or even know what + will be there. Force the caller to call refill_buffer(): + */ DBUG_RETURN(HA_ERR_END_OF_FILE); + } while (1) { @@ -374,24 +377,21 @@ int Mrr_ordered_index_reader::get_next(char **range_info_arg) /* Go get another (record, range_id) combination */ } /* while */ - memcpy(range_info_arg, cur_range_info, sizeof(void*)); + memcpy(range_info, cur_range_info, sizeof(void*)); DBUG_RETURN(0); } /** - DS-MRR/CPK: Fill the buffer with (lookup_tuple, range_id) pairs and sort - - Enumerate the input range (=key) sequence, fill the key buffer with - (lookup_key, range_id) pairs and sort it. - - When this function returns, either - - key buffer is non-empty, or - - key buffer is empty and source range sequence is exhausted - + Fill the buffer with (lookup_tuple, range_id) pairs and sort + @note - dsmrr_eof is set to indicate whether we've exhausted the list of ranges - we're scanning. + We don't know lookup_tuple before we get the first key from + mrr_funcs.get_next(). Not knowing tuple length means we can't setup the + key buffer (in particular, which part of the buffer space it should occupy + when we have both key and rowid buffers). This problem is solved by having + know_key_tuple_params variabe, and buf_manager, which we ask to set/reset + buffers for us. */ int Mrr_ordered_index_reader::refill_buffer() @@ -521,7 +521,7 @@ int Mrr_ordered_rndpos_reader::refill_buffer() if (index_reader_exhausted) DBUG_RETURN(HA_ERR_END_OF_FILE); - while ((res= refill2() == HA_ERR_END_OF_FILE)) + while ((res= refill_from_key_buffer() == HA_ERR_END_OF_FILE)) { if ((res= index_reader->refill_buffer())) { @@ -534,13 +534,23 @@ int Mrr_ordered_rndpos_reader::refill_buffer() } -/* This one refills without calling index_reader->refill_buffer(). */ -int Mrr_ordered_rndpos_reader::refill2() +void Mrr_index_reader::position() +{ + h->position(h->get_table()->record[0]); +} + + +/* + @brief Try to refill the rowid buffer without calling + index_reader->refill_buffer(). +*/ + +int Mrr_ordered_rndpos_reader::refill_from_key_buffer() { char *range_info; uchar **range_info_ptr= (uchar**)&range_info; int res; - DBUG_ENTER("Mrr_ordered_rndpos_reader::refill2"); + DBUG_ENTER("Mrr_ordered_rndpos_reader::refill_from_key_buffer"); DBUG_ASSERT(rowid_buffer->is_empty()); index_rowid= index_reader->get_rowid_ptr(); @@ -559,7 +569,7 @@ int Mrr_ordered_rndpos_reader::refill2() break; /* Put rowid, or {rowid, range_id} pair into the buffer */ - index_reader->h->position(index_reader->h->get_table()->record[0]); + index_reader->position(); rowid_buffer->write(); } @@ -574,10 +584,12 @@ int Mrr_ordered_rndpos_reader::refill2() } -/** - DS-MRR implementation: multi_range_read_next() function. +/* + Get the next record+range_id using ordered array of rowid+range_id pairds - Calling convention is like multi_range_read_next() has. + @note + Since we have sorted rowids, we try not to make multiple rnd_pos() calls + with the same rowid value. */ int Mrr_ordered_rndpos_reader::get_next(char **range_info) @@ -658,11 +670,8 @@ int Mrr_ordered_rndpos_reader::get_next(char **range_info) } -/************ Mrr_*_reader classes end ***************************************/ - - /**************************************************************************** - * DS-MRR implementation + * Top-level DS-MRR implementation functions (the ones called by storage engine) ***************************************************************************/ /** diff --git a/sql/multi_range_read.h b/sql/multi_range_read.h index aed8c2c1fa1..40b145f460c 100644 --- a/sql/multi_range_read.h +++ b/sql/multi_range_read.h @@ -122,7 +122,7 @@ public: /* - DS-MRR execution strategy abstraction. + Mrr_reader - DS-MRR execution strategy abstraction A reader produces ([index]_record, range_info) pairs, and requires periodic refill operations. @@ -142,27 +142,33 @@ class Mrr_reader public: virtual int get_next(char **range_info) = 0; virtual int refill_buffer() = 0; - virtual ~Mrr_reader() {}; /* just to remove compiler warning */ }; -/* A common base for strategies that do index scans and produce index tuples */ +/* + A common base for readers that do index scans and produce index tuples +*/ + class Mrr_index_reader : public Mrr_reader { +protected: + handler *h; /* Handler object to use */ public: - handler *h; - virtual int init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, void *seq_init_param, uint n_ranges, uint mode, Buffer_manager *buf_manager_arg) = 0; + + /* Get pointer to place where every get_next() call will put rowid */ virtual uchar *get_rowid_ptr()= 0; + /* Get the rowid (call this after get_next() call) */ + void position(); virtual bool skip_record(char *range_id, uchar *rowid)=0; }; /* - A "bypass" strategy that uses default MRR implementation (i.e. + A "bypass" reader that uses default MRR implementation (i.e. handler::multi_range_read_XXX() calls) to produce rows. */ @@ -184,9 +190,8 @@ public: }; - /* - A strategy that sorts index lookup keys before scanning the index + A reader that sorts the key values before it makes the index lookups. */ class Mrr_ordered_index_reader : public Mrr_index_reader @@ -238,7 +243,10 @@ private: }; -/* MRR strategy that fetches rowids */ +/* + A reader that gets rowids from an Mrr_index_reader, and then sorts them + before getting full records with handler->rndpos() calls. +*/ class Mrr_ordered_rndpos_reader : public Mrr_reader { @@ -266,10 +274,11 @@ private: uchar *rowid; uchar *rowids_range_id; - int refill2(); + int refill_from_key_buffer(); }; +/* A place where one can get readers without having to alloc them on the heap */ class Mrr_reader_factory { public: |