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110 lines
4.1 KiB
C++
110 lines
4.1 KiB
C++
/* Copyright (c) 2016 MariaDB corporation
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#ifndef UNIQUE_INCLUDED
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#define UNIQUE_INCLUDED
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#include "filesort.h"
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/*
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Unique -- class for unique (removing of duplicates).
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Puts all values to the TREE. If the tree becomes too big,
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it's dumped to the file. User can request sorted values, or
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just iterate through them. In the last case tree merging is performed in
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memory simultaneously with iteration, so it should be ~2-3x faster.
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*/
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class Unique :public Sql_alloc
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{
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DYNAMIC_ARRAY file_ptrs;
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ulong max_elements; /* Total number of elements that will be stored in-memory */
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size_t max_in_memory_size;
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IO_CACHE file;
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TREE tree;
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/* Number of elements filtered out due to min_dupl_count when storing results
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to table. See Unique::get */
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ulong filtered_out_elems;
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uint size;
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uint full_size; /* Size of element + space needed to store the number of
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duplicates found for the element. */
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uint min_dupl_count; /* Minimum number of occurences of element required for
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it to be written to record_pointers.
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always 0 for unions, > 0 for intersections */
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bool with_counters;
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bool merge(TABLE *table, uchar *buff, size_t size, bool without_last_merge);
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bool flush();
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public:
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ulong elements;
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SORT_INFO sort;
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Unique(qsort_cmp2 comp_func, void *comp_func_fixed_arg,
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uint size_arg, size_t max_in_memory_size_arg,
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uint min_dupl_count_arg= 0);
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~Unique();
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ulong elements_in_tree() { return tree.elements_in_tree; }
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inline bool unique_add(void *ptr)
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{
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DBUG_ENTER("unique_add");
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DBUG_PRINT("info", ("tree %u - %lu", tree.elements_in_tree, max_elements));
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if (!(tree.flag & TREE_ONLY_DUPS) &&
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tree.elements_in_tree >= max_elements && flush())
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DBUG_RETURN(1);
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DBUG_RETURN(!tree_insert(&tree, ptr, 0, tree.custom_arg));
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}
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bool is_in_memory() { return (my_b_tell(&file) == 0); }
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void close_for_expansion() { tree.flag= TREE_ONLY_DUPS; }
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bool get(TABLE *table);
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/* Cost of searching for an element in the tree */
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inline static double get_search_cost(ulonglong tree_elems,
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double compare_factor)
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{
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return log((double) tree_elems) * compare_factor / M_LN2;
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}
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static double get_use_cost(THD *thd, uint *buffer, size_t nkeys, uint key_size,
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size_t max_in_memory_size, double compare_factor,
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bool intersect_fl, bool *in_memory);
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inline static int get_cost_calc_buff_size(size_t nkeys, uint key_size,
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size_t max_in_memory_size)
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{
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size_t max_elems_in_tree=
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max_in_memory_size / ALIGN_SIZE(sizeof(TREE_ELEMENT)+key_size);
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if (max_elems_in_tree == 0)
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max_elems_in_tree= 1;
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return (int) (sizeof(uint)*(1 + nkeys/max_elems_in_tree));
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}
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void reset();
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bool walk(TABLE *table, tree_walk_action action, void *walk_action_arg);
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uint get_size() const { return size; }
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size_t get_max_in_memory_size() const { return max_in_memory_size; }
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friend int unique_write_to_file(void* key, element_count count, void *unique);
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friend int unique_write_to_ptrs(void* key, element_count count, void *unique);
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friend int unique_write_to_file_with_count(void *key, element_count count,
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void *unique);
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friend int unique_intersect_write_to_ptrs(void *key, element_count count,
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void *unique);
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};
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#endif /* UNIQUE_INCLUDED */
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