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Message #01436
MWL#24: Review feedback, first batch
Hello Igor,
Please find below the first portion of MWL#24 review feedback below. More to follow.
> diff -urN --exclude='.*' maria-5.1-wl24-clean2/sql/opt_range.cc maria-5.1-wl24-nocompile/sql/opt_range.cc
> --- maria-5.1-wl24-clean2/sql/opt_range.cc 2009-11-03 00:18:22.000000000 +0300
> +++ maria-5.1-wl24-nocompile/sql/opt_range.cc 2009-11-03 00:12:29.000000000 +0300
...
> @@ -809,96 +940,294 @@
>
>
> /*
> - Perform OR operation on this SEL_IMERGE and supplied SEL_TREE new_tree,
> - combining new_tree with one of the trees in this SEL_IMERGE if they both
> - have SEL_ARGs for the same key.
> + Check if any of the range trees of this imerge intersects with a given tree
>
> SYNOPSIS
> - or_sel_tree_with_checks()
> - param PARAM from SQL_SELECT::test_quick_select
There is be no need for this parameter since sel_trees_have_common_keys()
doesn't really need it.
> - new_tree SEL_TREE with type KEY or KEY_SMALLER.
> + have_common_keys()
> + param Context info for the function
> + tree SEL_TREE intersection with the imerge range trees is checked for
Unfinished sentence?
>
> - NOTES
> - This does the following:
> - (t_1||...||t_k)||new_tree =
> - either
> - = (t_1||...||t_k||new_tree)
> - or
> - = (t_1||....||(t_j|| new_tree)||...||t_k),
> + DESCRIPTION
> + The function checks whether there is any range tree rt_i in this imerge
> + such that there are some indexes for which ranges are defined in both
> + rt_i and the range part of the SEL_TREE tree.
> + To check this the function calls the function sel_trees_have_common_keys.
> +
> + RETURN
> + TRUE if there are such range trees in this imerge
> + FALSE otherwise
> +*/
> +
> +bool SEL_IMERGE::have_common_keys(RANGE_OPT_PARAM *param, SEL_TREE *tree)
> +{
> + for (SEL_TREE** or_tree= trees, **bound= trees_next;
> + or_tree != bound; or_tree++)
> + {
> + key_map common_keys;
> + if (sel_trees_have_common_keys(param, *or_tree, tree, &common_keys))
> + return TRUE;
> + }
> + return FALSE;
> +}
>
> - where t_i, y are SEL_TREEs.
> - new_tree is combined with the first t_j it has a SEL_ARG on common
> - key with. As a consequence of this, choice of keys to do index_merge
> - read may depend on the order of conditions in WHERE part of the query.
>
> +/*
> + Perform AND operation for this imerge and the range part of a tree
> +
> + SYNOPSIS
> + and_sel_tree()
> + param Context info for the operation
> + tree SEL_TREE for the second operand of the operation
> + new_imerge OUT imerge for the result of the operation
> +
> + DESCRIPTION
> + This function performs AND operation for this imerge m and the
> + range part of the SEL_TREE tree rt. In other words the function
^^^^ note that here it is 'rt' while
further on it is 'RT'.
> + pushes rt into this imerge. The resulting imerge is returned in
> + the parameter new_imerge.
> + If this imerge m represent the formula
> + RT_1 OR ... OR RT_k
> + then the resulting imerge of the function represents the formula
> + (RT_1 AND RT) OR ... (RT_k AND RT)
^^^ please add 'OR' here.
Overall, my personal opinion is that we should aim for more siccint comments,
for example, for this function the comment could be:
<comment>
This function performs an AND operation between this SEL_IMERGE object and
a given SEL_TREE object. It performs the following conversion:
(rt_1 OR ... OR rt_k) AND rt -> (rt_1 AND rt) OR ... OR (rt_k AND rt)
We call and_range_trees() function to construct a SEL_TREE for (rt_i AND rt).
</comment>
> + The function calls the function and_range_trees to construct the
> + range tree representing (RT_i AND RT).
imho there is not much merit in providing details like that (or I'm missing
something important here)
> +
> + NOTE
> + The function may return an empty imerge without any range trees
while here it would be helpful to have another sentense explaining when this
can happen and what does returning empty imerge means. (does it mean that
there is no records that would match both given SEL_IMERGE and SEL_TREE?)
> +
> RETURN
> - 0 OK
> - 1 One of the trees was combined with new_tree to SEL_TREE::ALWAYS,
> - and (*this) should be discarded.
> - -1 An error occurred.
> + 0 if the operation is a success
> + -1 otherwise: there is not enough memory to perform the operation
> */
>
> -int SEL_IMERGE::or_sel_tree_with_checks(RANGE_OPT_PARAM *param, SEL_TREE *new_tree)
> +int SEL_IMERGE::and_sel_tree(RANGE_OPT_PARAM *param, SEL_TREE *tree,
> + SEL_IMERGE *new_imerge)
If the function can only return two possible values, can its return type be
changed to bool?
> {
> - for (SEL_TREE** tree = trees;
> - tree != trees_next;
> - tree++)
> + for (SEL_TREE** or_tree= trees; or_tree != trees_next; or_tree++)
> {
> - if (sel_trees_can_be_ored(*tree, new_tree, param))
> + SEL_TREE *result= 0;
The name 'result' is typically used to store the result of entire function.
This function will typically produce multiple 'results', which is confusing.
Please rename the variable.
> + key_map result_keys;
> + if (!(result= new SEL_TREE()))
> + return (-1);
> + if (!and_range_trees(param, *or_tree, tree, result))
> {
> - *tree = tree_or(param, *tree, new_tree);
> - if (!*tree)
> - return 1;
> - if (((*tree)->type == SEL_TREE::MAYBE) ||
> - ((*tree)->type == SEL_TREE::ALWAYS))
> + if (new_imerge->or_sel_tree(param, result))
> + return (-1);
> + }
> + }
> + return 0;
> +}
> +
> +
> +/*
> + Perform OR operation on this imerge and the range part of a tree
> +
> + SYNOPSIS
> + or_sel_tree_with_checks()
> + param Context info for the operation
> + tree SEL_TREE whose range part is to be ored
> + is_first_check_pass <=> the first call of the function for this imerge
> + is_last_check_pass OUT <=> no more calls of the function for this imerge
> +
> + DESCRIPTION
> + The functions performs OR operation on this imerge m and the range part
"functions performs", bad grammar.
Why denote the imerge as "m" if we don't use "m" later on?
> + of the SEL_TREE tree rt. It always replaces this imerge with the result
> + of the operation.
> +
> + The operation can be performed in two different modes: with
> + is_first_check_pass==TRUE and is_first_check_pass==FALSE, transforming
> + this imerge differently.
> +
> + Given this imerge represents the formula
> + RT_1 OR ... OR RT_k:
> +
> + 1. In the first mode, when is_first_check_pass==TRUE :
Is there really a need to be be so verbose, s/In the first mode,// ?
> + 1.1. If rt must be ored(see the function sel_trees_must_be_ored) with
Would it be shorter if "see the function sel_trees_must_be_ored" was changed to
"see sel_trees_must_be_ored()"?
> + some rt_j (there may be only one such range tree in the imerge)
> + then the function produces the imerge representing the formula
s/the imerge/an imerge/ ?
> + RT_1 OR ... OR (RT_j OR RT) OR ... OR RT_k,
> + where the tree for (RT_j OR RT) is built by oring the pairs
s/oring/ORing/ ?
> + of SEL_ARG trees for the corresponding indexes
> + 1.2. Otherwise the function produces the imerge representing the formula:
> + RT_1 OR ... OR RT_k OR RT.
> +
> + 2. In the second mode, when is_first_check_pass==FALSE :
> + 2.1. For each rt_j in the imerge that can be ored (see the function
> + sel_trees_can_be_ored), but not must be ored, with rt the function
> + replaces rt_j for a range tree such that for each index for which
> + ranges are defined in both in rt_j and rt the tree contains the
> + result of oring of these ranges.
> + 2.2. In other cases the function does not produce any imerge.
> +
> + When is_first_check==TRUE the function returns FALSE in the parameter
> + is_last_check_pass if there is no rt_j such that rt_j can be ored with rt,
> + but, at the same time, it's not true that rt_j must be ored with rt.
> + When is_first_check==FALSE the function always returns FALSE in the
> + parameter is_last_check_pass.
> +
> + RETURN
> + 1 The result of oring of rt_j and rt that must be ored returns the
> + the range tree with type==SEL_TREE::ALWAYS
> + (in this case the imerge m should be discarded)
> + -1 The function runs out of memory
> + 0 in all other cases
> +*/
> +
> +int SEL_IMERGE::or_sel_tree_with_checks(RANGE_OPT_PARAM *param,
> + SEL_TREE *tree,
> + bool is_first_check_pass,
> + bool *is_last_check_pass)
> +{
> + *is_last_check_pass= TRUE;
> + for (SEL_TREE** or_tree = trees;
> + or_tree != trees_next;
> + or_tree++)
> + {
> + SEL_TREE *result= 0;
> + key_map result_keys;
> + key_map ored_keys;
> + if (sel_trees_can_be_ored(param, *or_tree, tree, &ored_keys))
> + {
> + bool must_be_ored= sel_trees_must_be_ored(param, *or_tree, tree,
> + ored_keys);
> + if (must_be_ored == is_first_check_pass) {
^^^^^^
Coding style violation
> + result_keys.clear_all();
> + result= *or_tree;
> + for (uint key_no= 0; key_no < param->keys; key_no++)
> + {
> + if (!ored_keys.is_set(key_no))
> + {
> + result->keys[key_no]= 0;
> + continue;
> + }
> + SEL_ARG *key1= (*or_tree)->keys[key_no];
> + SEL_ARG *key2= tree->keys[key_no];
> + key2->incr_refs();
> + if ((result->keys[key_no]= key_or(param, key1, key2)))
> + {
> +
> + result_keys.set_bit(key_no);
> +#ifdef EXTRA_DEBUG
> + if (param->alloced_sel_args < SEL_ARG::MAX_SEL_ARGS)
> + {
> + key1= result->keys[key_no];
> + (key1)->test_use_count(key1);
> + }
> +#endif
> + }
> + }
> + }
> + else if(is_first_check_pass)
> + *is_last_check_pass= FALSE;
> + }
> +
> + if (result)
> + {
> + if (result_keys.is_clear_all())
> + result->type= SEL_TREE::ALWAYS;
> + *is_last_check_pass= TRUE;
> + if ((result->type == SEL_TREE::MAYBE) ||
> + (result->type == SEL_TREE::ALWAYS))
> return 1;
> /* SEL_TREE::IMPOSSIBLE is impossible here */
> - return 0;
> + result->keys_map= result_keys;
> + *or_tree= result;
> + if (is_first_check_pass)
> + return 0;
> }
> }
> + if (!is_first_check_pass)
> + return 0;
>
> - /* New tree cannot be combined with any of existing trees. */
> - return or_sel_tree(param, new_tree);
> + if (!*is_last_check_pass &&
> + !(tree= new SEL_TREE(tree, FALSE, param)))
> + return (-1);
> + return or_sel_tree(param, tree);
> }
>
>
> /*
> - Perform OR operation on this index_merge and supplied index_merge list.
> + Perform OR operation on this imerge and and another imerge
> +
> + SYNOPSIS
> + or_sel_tree_with_checks()
> + param Context info for the operation
> + imerge The second operand of the operation
> + is_first_check_pass <=> the first call of the function for this imerge
> + is_last_check_pass OUT <=> no more calls of the function for this imerge
>
> + DESCRIPTION
> + For each range tree rt from 'imerge' the function calls the method
> + SEL_IMERGE::or_sel_tree_with_checks that performs OR operation on this
> + SEL_IMERGE object m and the tree rt. The mode of the operation is
> + specified by the parameter is_first_check_pass. Each call of
> + SEL_IMERGE::or_sel_tree_with_checks transforms this SEL_IMERGE object m.
> + The function returns FALSE in the prameter is_last_check_pass if
> + at least one of the calls of SEL_IMERGE::or_sel_tree_with_checks
> + returns FALSE as the value of its last parameter.
> +
> RETURN
> - 0 - OK
> - 1 - One of conditions in result is always TRUE and this SEL_IMERGE
> - should be discarded.
> - -1 - An error occurred
> + 1 One of the calls of SEL_IMERGE::or_sel_tree_with_checks returns 1.
> + (in this case the imerge m should be discarded)
> + -1 The function runs out of memory
> + 0 in all other cases
> */
>
> -int SEL_IMERGE::or_sel_imerge_with_checks(RANGE_OPT_PARAM *param, SEL_IMERGE* imerge)
> +int SEL_IMERGE::or_sel_imerge_with_checks(RANGE_OPT_PARAM *param,
> + SEL_IMERGE* imerge,
> + bool is_first_check_pass,
> + bool *is_last_check_pass)
> {
> + *is_last_check_pass= TRUE;
> for (SEL_TREE** tree= imerge->trees;
> tree != imerge->trees_next;
> tree++)
> {
> - if (or_sel_tree_with_checks(param, *tree))
> - return 1;
> + uint rc;
> + bool is_last;
> + rc= or_sel_tree_with_checks(param, *tree, is_first_check_pass, &is_last);
> + if (!is_last)
> + *is_last_check_pass= FALSE;
> + if (rc)
> + return rc;
> }
> return 0;
> }
>
>
> -SEL_TREE::SEL_TREE(SEL_TREE *arg, RANGE_OPT_PARAM *param): Sql_alloc()
> +/*
> + Copy constructor for SEL_TREE objects
> +
> + SYNOPSIS
> + SEL_TREE
> + arg The source tree for the constructor
> + without_merges <=> only the range part of the tree arg is copied
> + param Context info for the operation
> +
> + DESCRIPTION
> + The constructor creates a full copy of the SEL_TREE arg if
> + the prameter without_merges==FALSE. Otherwise a tree is created
> + that contains the copy only of the range part of the tree arg.
> +*/
> +
> +SEL_TREE::SEL_TREE(SEL_TREE *arg, bool without_merges,
> + RANGE_OPT_PARAM *param): Sql_alloc()
> {
> keys_map= arg->keys_map;
> type= arg->type;
> - for (int idx= 0; idx < MAX_KEY; idx++)
> + for (uint idx= 0; idx < param->keys; idx++)
> {
> if ((keys[idx]= arg->keys[idx]))
> - keys[idx]->increment_use_count(1);
> + keys[idx]->incr_refs();
> }
>
> + if (without_merges)
> + return;
> +
> List_iterator<SEL_IMERGE> it(arg->merges);
> for (SEL_IMERGE *el= it++; el; el= it++)
> {
> - SEL_IMERGE *merge= new SEL_IMERGE(el, param);
> + SEL_IMERGE *merge= new SEL_IMERGE(el, 0, param);
> if (!merge || merge->trees == merge->trees_next)
> {
> merges.empty();
> @@ -909,7 +1238,23 @@
> }
>
>
> -SEL_IMERGE::SEL_IMERGE (SEL_IMERGE *arg, RANGE_OPT_PARAM *param) : Sql_alloc()
> +/*
> + Copy constructor for SEL_IMERGE objects
> +
> + SYNOPSIS
> + SEL_IMERGE
> + arg The source imerge for the constructor
> + cnt How many trees from arg are to be copied
> + param Context info for the operation
> +
> + DESCRIPTION
> + The cnt==0 then the constructor creates a full copy of the
> + imerge arg. Otherwise only the first cnt trees of the imerge
> + are copied.
> +*/
> +
> +SEL_IMERGE::SEL_IMERGE(SEL_IMERGE *arg, uint cnt,
> + RANGE_OPT_PARAM *param) : Sql_alloc()
> {
> uint elements= (arg->trees_end - arg->trees);
> if (elements > PREALLOCED_TREES)
> @@ -921,13 +1266,13 @@
> else
> trees= &trees_prealloced[0];
>
> - trees_next= trees;
> + trees_next= trees + (cnt ? cnt : arg->trees_next-arg->trees);
> trees_end= trees + elements;
>
> - for (SEL_TREE **tree = trees, **arg_tree= arg->trees; tree < trees_end;
> + for (SEL_TREE **tree = trees, **arg_tree= arg->trees; tree < trees_next;
> tree++, arg_tree++)
> {
> - if (!(*tree= new SEL_TREE(*arg_tree, param)))
> + if (!(*tree= new SEL_TREE(*arg_tree, FALSE, param)))
> goto mem_err;
> }
>
> @@ -941,7 +1286,19 @@
>
>
> /*
> - Perform AND operation on two index_merge lists and store result in *im1.
> + Perform AND operation on two imerge lists
> +
> + SYNOPSIS
> + imerge_list_and_list()
> + param Context info for the operation
> + im1 The first imerge list for the operation
> + im2 The second imerge list for the operation
> +
> + DESCRIPTION
> + The function just appends the imerge list im2 to the imerge list im1
> +
> + RETURN VALUE
> + none
> */
>
> inline void imerge_list_and_list(List<SEL_IMERGE> *im1, List<SEL_IMERGE> *im2)
> @@ -951,73 +1308,242 @@
>
>
> /*
> - Perform OR operation on 2 index_merge lists, storing result in first list.
> -
> - NOTES
> - The following conversion is implemented:
> - (a_1 &&...&& a_N)||(b_1 &&...&& b_K) = AND_i,j(a_i || b_j) =>
> - => (a_1||b_1).
> -
> - i.e. all conjuncts except the first one are currently dropped.
> - This is done to avoid producing N*K ways to do index_merge.
> + Perform OR operation on two imerge lists
>
> - If (a_1||b_1) produce a condition that is always TRUE, NULL is returned
> - and index_merge is discarded (while it is actually possible to try
> - harder).
> -
> - As a consequence of this, choice of keys to do index_merge read may depend
> - on the order of conditions in WHERE part of the query.
> + SYNOPSIS
> + imerge_list_or_list()
> + param Context info for the operation
> + im1 The first imerge list for the operation
> + im2 The second imerge list for the operation
> +
> + DESCRIPTION
> + Assuming that the first imerge list represents the formula
> + F1= M1_1 AND ... AND M1_k1
> + while the second imerge list represents the formula
> + F2= M2_1 AND ... AND M2_k2,
> + where M1_i= RT1_i_1 OR ... OR RT1_i_l1i (i in [1..k1])
> + and M2_i = RT2_i_1 OR ... OR RT2_i_l2i (i in [1..k2]),
> + the function builds a list of imerges for some formula that can be
> + inferred from the formula (F1 OR F2).
> +
> + More exactly the function builds imerges for the formula (M1_1 OR M2_1).
> + Note that
> + (F1 OR F2) = (M1_1 AND ... AND M1_k1) OR (M2_1 AND ... AND M2_k2) =
> + AND (M1_i OR M2_j) (i in [1..k1], j in [1..k2]) =>
> + M1_1 OR M2_1.
> + So (M1_1 OR M2_1) is indeed an inference formula for (F1 OR F2).
> +
> + To build imerges for the formula (M1_1 OR M2_1) the function invokes,
> + possibly twice, the method SEL_IMERGE::or_sel_imerge_with_checks
> + for the imerge m1_1.
> + At its first invocation the method SEL_IMERGE::or_sel_imerge_with_checks
> + performs OR operation on the imerge m1_1 and the range tree rt2_1_1 by
> + calling SEL_IMERGE::or_sel_tree_with_checks with is_first_pass_check==TRUE.
> + The resulting imerge of the operation is ored with the next range tree of
> + the imerge m2_1. This oring continues until the last range tree from
> + m2_1 has been ored.
> + At its second invocation the method SEL_IMERGE::or_sel_imerge_with_checks
> + performs the same sequence of OR operations, but now calling
> + SEL_IMERGE::or_sel_tree_with_checks with is_first_pass_check==FALSE.
>
> + The imerges that the operation produces replace those in the list im1
> +
> RETURN
> - 0 OK, result is stored in *im1
> - other Error, both passed lists are unusable
> + 0 if the operation is a success
> + -1 if the function has run out of memory
> */
>
> int imerge_list_or_list(RANGE_OPT_PARAM *param,
> List<SEL_IMERGE> *im1,
> List<SEL_IMERGE> *im2)
> {
> +
> + uint rc;
> + bool is_last_check_pass= FALSE;
> +
> SEL_IMERGE *imerge= im1->head();
> + uint elems= imerge->trees_next-imerge->trees;
> im1->empty();
> im1->push_back(imerge);
>
> - return imerge->or_sel_imerge_with_checks(param, im2->head());
> + rc= imerge->or_sel_imerge_with_checks(param, im2->head(),
> + TRUE, &is_last_check_pass);
> + if (rc)
> + {
> + if (rc == 1)
> + {
> + im1->empty();
> + rc= 0;
> + }
> + return rc;
> + }
> +
> + if (!is_last_check_pass)
> + {
> + SEL_IMERGE* new_imerge= new SEL_IMERGE(imerge, elems, param);
> + if (new_imerge)
> + {
> + is_last_check_pass= TRUE;
> + rc= new_imerge->or_sel_imerge_with_checks(param, im2->head(),
> + FALSE, &is_last_check_pass);
> + if (!rc)
> + im1->push_back(new_imerge);
> + }
> + }
> + return rc;
> }
>
>
> /*
> - Perform OR operation on index_merge list and key tree.
> + Perform OR operation for each imerge from a list and the range part of a tree
> +
> + SYNOPSIS
> + imerge_list_or_tree()
> + param Context info for the operation
> + merges The list of imerges to be ored with the range part of tree
> + tree SEL_TREE whose range part is to be ored with the imerges
>
> + DESCRIPTION
> + For each imerge mi from the list 'merges' the function performes OR
> + operation with mi and the range part of 'tree' rt, producing one or
> + two imerges.
> +
> + Given the merge mi represent the formula RTi_1 OR ... OR RTi_k,
> + the function forms the merges by the following rules:
> +
> + 1. If rt cannot be ored with any of the trees rti the function just
> + produces an imerge that represents the formula
> + RTi_1 OR ... RTi_k OR RT.
> + 2. If there exist a tree rtj that must be ored with rt the function
> + produces an imerge the represents the formula
> + RTi_1 OR ... OR (RTi_j OR RT) OR ... OR RTi_k,
> + where the range tree for (RTi_j OR RT) is constructed by oring the
> + SEL_ARG trees that must be ored.
> + 3. For each rti_j that can be ored with rt the function produces
> + the new tree rti_j' and substitutes rti_j for this new range tree.
> +
> + In any case the function removes mi from the list and then adds all
> + produced imerges.
> +
> + To build imerges by rules 1-3 the function calls the method
> + SEL_IMERGE::or_sel_tree_with_checks, possibly twice. With the first
> + call it passes TRUE for the third parameter of the function.
> + At this first call imerges by rules 1-2 are built. If the call
> + returns FALSE as the return value of its fourth parameter then the
> + function are called for the second time. At this call the imerge
> + of rule 3 is produced.
> +
> + If a call of SEL_IMERGE::or_sel_tree_with_checks returns 1 then
> + then it means that the produced tree contains an always true
> + range tree and the whole imerge can be discarded.
> +
> RETURN
> - 0 OK, result is stored in *im1.
> - other Error
> + 1 if no imerges are produced
> + 0 otherwise
> */
>
> +static
> int imerge_list_or_tree(RANGE_OPT_PARAM *param,
> - List<SEL_IMERGE> *im1,
> + List<SEL_IMERGE> *merges,
> SEL_TREE *tree)
> {
> +
> SEL_IMERGE *imerge;
> - List_iterator<SEL_IMERGE> it(*im1);
> - bool tree_used= FALSE;
> + List<SEL_IMERGE> additional_merges;
> + List_iterator<SEL_IMERGE> it(*merges);
> +
> while ((imerge= it++))
> {
> - SEL_TREE *or_tree;
> - if (tree_used)
> - {
> - or_tree= new SEL_TREE (tree, param);
> - if (!or_tree ||
> - (or_tree->keys_map.is_clear_all() && or_tree->merges.is_empty()))
> - return FALSE;
> + bool is_last_check_pass;
> + int rc= 0;
> + int rc1= 0;
> + SEL_TREE *or_tree= new SEL_TREE (tree, FALSE, param);
> + if (or_tree)
> + {
> + uint elems= imerge->trees_next-imerge->trees;
> + rc= imerge->or_sel_tree_with_checks(param, or_tree,
> + TRUE, &is_last_check_pass);
> + if (!is_last_check_pass)
> + {
> + SEL_IMERGE *new_imerge= new SEL_IMERGE(imerge, elems, param);
> + if (new_imerge)
> + {
> + rc1= new_imerge->or_sel_tree_with_checks(param, or_tree,
> + FALSE, &is_last_check_pass);
> + if (!rc1)
> + additional_merges.push_back(new_imerge);
> + }
> + }
> }
> - else
> - or_tree= tree;
> -
> - if (imerge->or_sel_tree_with_checks(param, or_tree))
> + if (rc || rc1 || !or_tree)
> it.remove();
> - tree_used= TRUE;
> }
> - return im1->is_empty();
> +
> + merges->concat(&additional_merges);
> + return merges->is_empty();
> +}
> +
> +
> +/*
> + Perform pushdown operation of the range part of a tree into given imerges
> +
> + SYNOPSIS
> + imerge_list_and_tree()
> + param Context info for the operation
> + merges IN/OUT List of imerges to push the range part of 'tree' into
> + tree SEL_TREE whose range part is to be pushed into imerges
> +
> + DESCRIPTION
> + For each imerge from the list merges the function pushes the range part
> + rt of 'tree' into the imerge.
> + More exactly if the imerge mi from the list represents the formula
> + RTi_1 OR ... OR RTi_k
> + the function bulds a new imerge that represents the formula
> + (RTi_1 AND RT) OR ... OR (RTi_k AND RT)
Where the "RT" is? I think the comment would be much easier to read if the
conversion was explicitly specified.
> + and adds this imerge to the list merges.
> + To perform this pushdown operation the function calls the method
> + SEL_IMERGE::and_sel_tree.
> + For any imerge mi the new imerge is not created if for each pair of
> + trees rti_j and rt the intersection of the indexes with defined ranges
> + is empty.
> + If the result of the pushdown operation for the imerge mi returns an
> + imerge with no trees then then not only nothing is added to the list
> + merges but mi itself is removed from the list.
> +
> + RETURN
> + 1 if no imerges are left in the list merges
> + 0 otherwise
> +*/
> +
> +static
> +int imerge_list_and_tree(RANGE_OPT_PARAM *param,
> + List<SEL_IMERGE> *merges,
> + SEL_TREE *tree)
> +{
> + SEL_IMERGE *imerge;
> + SEL_IMERGE *new_imerge= NULL;
> + List<SEL_IMERGE> new_merges;
> + List_iterator<SEL_IMERGE> it(*merges);
> +
> + while ((imerge= it++))
> + {
> + if (!new_imerge)
> + new_imerge= new SEL_IMERGE();
> + if (imerge->have_common_keys(param, tree) &&
> + new_imerge && !imerge->and_sel_tree(param, tree, new_imerge))
> + {
> + if (new_imerge->trees == new_imerge->trees_next)
> + it.remove();
> + else
> + {
> + new_merges.push_back(new_imerge);
> + new_imerge= NULL;
> + }
> + }
> + }
> + imerge_list_and_list(&new_merges, merges);
> + *merges= new_merges;
> + return merges->is_empty();
> }
>
>
> @@ -1651,6 +2177,7 @@
> min_value=arg.min_value;
> max_value=arg.max_value;
> next_key_part=arg.next_key_part;
> + max_part_no= arg.max_part_no;
> use_count=1; elements=1;
> }
>
> @@ -1668,9 +2195,10 @@
> :min_flag(0), max_flag(0), maybe_flag(0), maybe_null(f->real_maybe_null()),
> elements(1), use_count(1), field(f), min_value((uchar*) min_value_arg),
> max_value((uchar*) max_value_arg), next(0),prev(0),
> - next_key_part(0),color(BLACK),type(KEY_RANGE)
> + next_key_part(0), color(BLACK), type(KEY_RANGE)
> {
> left=right= &null_element;
> + max_part_no= 1;
> }
>
> SEL_ARG::SEL_ARG(Field *field_,uint8 part_,
> @@ -1681,6 +2209,7 @@
> field(field_), min_value(min_value_), max_value(max_value_),
> next(0),prev(0),next_key_part(0),color(BLACK),type(KEY_RANGE)
> {
> + max_part_no= part+1;
> left=right= &null_element;
> }
>
> @@ -1723,6 +2252,7 @@
> increment_use_count(1);
> tmp->color= color;
> tmp->elements= this->elements;
> + tmp->max_part_no= max_part_no;
> return tmp;
> }
>
> @@ -2367,72 +2897,73 @@
> It is possible to use a range-based quick select (but it might be
> slower than 'all' table scan).
> */
> - if (tree->merges.is_empty())
> + TRP_RANGE *range_trp;
> + TRP_ROR_INTERSECT *rori_trp;
> + bool can_build_covering= FALSE;
> +
> + remove_nonrange_trees(¶m, tree);
> +
> + /* Get best 'range' plan and prepare data for making other plans */
> + if ((range_trp= get_key_scans_params(¶m, tree, FALSE, TRUE,
> + best_read_time)))
> {
> - TRP_RANGE *range_trp;
> - TRP_ROR_INTERSECT *rori_trp;
> - bool can_build_covering= FALSE;
> -
> - /* Get best 'range' plan and prepare data for making other plans */
> - if ((range_trp= get_key_scans_params(¶m, tree, FALSE, TRUE,
> - best_read_time)))
> - {
> - best_trp= range_trp;
> - best_read_time= best_trp->read_cost;
> - }
> + best_trp= range_trp;
> + best_read_time= best_trp->read_cost;
> + }
>
> + /*
> + Simultaneous key scans and row deletes on several handler
> + objects are not allowed so don't use ROR-intersection for
> + table deletes.
> + */
> + if ((thd->lex->sql_command != SQLCOM_DELETE) &&
> + optimizer_flag(thd, OPTIMIZER_SWITCH_INDEX_MERGE))
> + {
> /*
> - Simultaneous key scans and row deletes on several handler
> - objects are not allowed so don't use ROR-intersection for
> - table deletes.
> + Get best non-covering ROR-intersection plan and prepare data for
> + building covering ROR-intersection.
> */
> - if ((thd->lex->sql_command != SQLCOM_DELETE) &&
> - optimizer_flag(thd, OPTIMIZER_SWITCH_INDEX_MERGE))
> + if ((rori_trp= get_best_ror_intersect(¶m, tree, best_read_time,
> + &can_build_covering)))
> {
> + best_trp= rori_trp;
> + best_read_time= best_trp->read_cost;
> /*
> - Get best non-covering ROR-intersection plan and prepare data for
> - building covering ROR-intersection.
> + Try constructing covering ROR-intersect only if it looks possible
> + and worth doing.
> */
> - if ((rori_trp= get_best_ror_intersect(¶m, tree, best_read_time,
> - &can_build_covering)))
> - {
> + if (!rori_trp->is_covering && can_build_covering &&
> + (rori_trp= get_best_covering_ror_intersect(¶m, tree,
> + best_read_time)))
> best_trp= rori_trp;
> - best_read_time= best_trp->read_cost;
> - /*
> - Try constructing covering ROR-intersect only if it looks possible
> - and worth doing.
> - */
> - if (!rori_trp->is_covering && can_build_covering &&
> - (rori_trp= get_best_covering_ror_intersect(¶m, tree,
> - best_read_time)))
> - best_trp= rori_trp;
> - }
> }
> }
> - else
> +
> + if (optimizer_flag(thd, OPTIMIZER_SWITCH_INDEX_MERGE))
> {
> - if (optimizer_flag(thd, OPTIMIZER_SWITCH_INDEX_MERGE))
> + /* Try creating index_merge/ROR-union scan. */
> + SEL_IMERGE *imerge;
> + TABLE_READ_PLAN *best_conj_trp= NULL, *new_conj_trp;
> + LINT_INIT(new_conj_trp); /* no empty index_merge lists possible */
> + DBUG_PRINT("info",("No range reads possible,"
> + " trying to construct index_merge"));
> + List_iterator_fast<SEL_IMERGE> it(tree->merges);
> + while ((imerge= it++))
> {
> - /* Try creating index_merge/ROR-union scan. */
> - SEL_IMERGE *imerge;
> - TABLE_READ_PLAN *best_conj_trp= NULL, *new_conj_trp;
> - LINT_INIT(new_conj_trp); /* no empty index_merge lists possible */
> - DBUG_PRINT("info",("No range reads possible,"
> - " trying to construct index_merge"));
> - List_iterator_fast<SEL_IMERGE> it(tree->merges);
> - while ((imerge= it++))
> + new_conj_trp= get_best_disjunct_quick(¶m, imerge, best_read_time);
> + if (new_conj_trp)
> + set_if_smaller(param.table->quick_condition_rows,
> + new_conj_trp->records);
> + if (new_conj_trp &&
> + (!best_conj_trp ||
> + new_conj_trp->read_cost < best_conj_trp->read_cost))
> {
> - new_conj_trp= get_best_disjunct_quick(¶m, imerge, best_read_time);
> - if (new_conj_trp)
> - set_if_smaller(param.table->quick_condition_rows,
> - new_conj_trp->records);
> - if (!best_conj_trp || (new_conj_trp && new_conj_trp->read_cost <
> - best_conj_trp->read_cost))
> - best_conj_trp= new_conj_trp;
> + best_conj_trp= new_conj_trp;
> + best_read_time= best_conj_trp->read_cost;
> }
> - if (best_conj_trp)
> - best_trp= best_conj_trp;
> }
> + if (best_conj_trp)
> + best_trp= best_conj_trp;
> }
> }
>
> @@ -3696,7 +4227,6 @@
> {
> SEL_TREE **ptree;
> TRP_INDEX_MERGE *imerge_trp= NULL;
> - uint n_child_scans= imerge->trees_next - imerge->trees;
> TRP_RANGE **range_scans;
> TRP_RANGE **cur_child;
> TRP_RANGE **cpk_scan= NULL;
> @@ -3716,6 +4246,24 @@
> DBUG_ENTER("get_best_disjunct_quick");
> DBUG_PRINT("info", ("Full table scan cost: %g", read_time));
>
> + /*
> + In every tree of imerge remove SEL_ARG trees that do not make ranges.
> + If after this removal some SEL_ARG tree becomes empty discard imerge.
> + */
> + for (ptree= imerge->trees; ptree != imerge->trees_next; ptree++)
> + {
> + if (remove_nonrange_trees(param, *ptree))
> + {
> + imerge->trees_next= imerge->trees;
> + break;
> + }
> + }
> +
> + uint n_child_scans= imerge->trees_next - imerge->trees;
> +
> + if (!n_child_scans)
> + DBUG_RETURN(NULL);
> +
> if (!(range_scans= (TRP_RANGE**)alloc_root(param->mem_root,
> sizeof(TRP_RANGE*)*
> n_child_scans)))
> @@ -3835,6 +4383,13 @@
> imerge_trp->range_scans_end= range_scans + n_child_scans;
> read_time= imerge_cost;
> }
> + if (imerge_trp)
> + {
> + TABLE_READ_PLAN *trp= merge_same_index_scans(param, imerge, imerge_trp,
> + read_time);
> + if (trp != imerge_trp)
> + DBUG_RETURN(trp);
> + }
> }
>
> build_ror_index_merge:
> @@ -3850,6 +4405,7 @@
> sizeof(TABLE_READ_PLAN*)*
> n_child_scans)))
> DBUG_RETURN(imerge_trp);
> +
> skip_to_ror_scan:
> roru_index_costs= 0.0;
> roru_total_records= 0;
> @@ -3933,7 +4489,116 @@
> DBUG_RETURN(roru);
> }
> }
> - DBUG_RETURN(imerge_trp);
> + DBUG_RETURN(imerge_trp);
> +}
> +
> +
> +/*
> + Merge index scans for the same indexes in an index merge plan
> +
> + SYNOPSIS
> + merge_same_index_scans()
> + param Context info for the operation
> + imerge IN/OUT SEL_IMERGE from which imerge_trp has been extracted
> + imerge_trp The index merge plan where index scans for the same
> + indexes are to be merges
> + read_time The upper bound for the cost of the plan to be evaluated
> +
> + DESRIPTION
> + For the given index merge plan imerge_trp extracted from the SEL_MERGE
> + imerge the function looks for range scans with the same indexes and merges
> + them into SEL_ARG trees. Then for each such SEL_ARG tree r_i the function
> + creates a range tree rt_i that contains only r_i. All rt_i are joined
> + into one index merge that replaces the original index merge imerge.
> + The function calls get_best_disjunct_quick for the new index merge to
> + get a new index merge plan that contains index scans only for different
> + indexes.
> + If there are no index scans for the same index in the original index
> + merge plan the function does not change the original imerge and returns
> + imerge_trp as its result.
> +
> + RETURN
> + The original or or improved index merge plan
> +*/
> +
> +static
> +TABLE_READ_PLAN *merge_same_index_scans(PARAM *param, SEL_IMERGE *imerge,
> + TRP_INDEX_MERGE *imerge_trp,
> + double read_time)
> +{
> + uint16 first_scan_tree_idx[MAX_KEY];
> + SEL_TREE **tree;
> + TRP_RANGE **cur_child;
> + uint removed_cnt= 0;
> +
> + DBUG_ENTER("merge_same_index_scans");
> +
> + bzero(first_scan_tree_idx, sizeof(first_scan_tree_idx[0])*param->keys);
> +
> + for (tree= imerge->trees, cur_child= imerge_trp->range_scans;
> + tree != imerge->trees_next;
> + tree++, cur_child++)
> + {
> + DBUG_ASSERT(tree);
> + uint key_idx= (*cur_child)->key_idx;
> + uint16 *tree_idx_ptr= &first_scan_tree_idx[key_idx];
> + if (!*tree_idx_ptr)
> + *tree_idx_ptr= (uint16) (tree-imerge->trees+1);
> + else
> + {
> + SEL_TREE **changed_tree= imerge->trees+(*tree_idx_ptr-1);
> + SEL_ARG *key= (*changed_tree)->keys[key_idx];
> + bzero((*changed_tree)->keys,
> + sizeof((*changed_tree)->keys[0])*param->keys);
> + (*changed_tree)->keys_map.clear_all();
> + if (((*changed_tree)->keys[key_idx]=
> + key_or(param, key, (*tree)->keys[key_idx])))
> + (*changed_tree)->keys_map.set_bit(key_idx);
> + *tree= NULL;
> + removed_cnt++;
> + }
> + }
> + if (!removed_cnt)
> + DBUG_RETURN(imerge_trp);
> +
> + TABLE_READ_PLAN *trp= NULL;
> + SEL_TREE **new_trees_next= imerge->trees;
> + for (tree= new_trees_next; tree != imerge->trees_next; tree++)
> + {
> + if (!*tree)
> + continue;
> + if (tree > new_trees_next)
> + *new_trees_next= *tree;
> + new_trees_next++;
> + }
> + imerge->trees_next= new_trees_next;
> +
> + DBUG_ASSERT(imerge->trees_next>imerge->trees);
> +
> + if (imerge->trees_next-imerge->trees > 1)
> + trp= get_best_disjunct_quick(param, imerge, read_time);
> + else
> + {
> + /*
> + This alternative theoretically can be reached when the cost
> + of the index merge for such a formula as
> + (key1 BETWEEN c1_1 AND c1_2) AND key2 > c2 OR
> + (key1 BETWEEN c1_3 AND c1_4) AND key3 > c3
> + is estimated as being cheaper than the cost of index scan for
> + the formula
> + (key1 BETWEEN c1_1 AND c1_2) OR (key1 BETWEEN c1_3 AND c1_4)
> +
> + In the current code this may happen for two reasons:
> + 1. for a single index range scan data records are accessed in
> + a random order
> + 2. the functions that estimate the cost of a range scan and an
> + index merge retrievals are not well calibrated
> + */
> + trp= get_key_scans_params(param, *imerge->trees, FALSE, TRUE,
> + read_time);
> + }
> +
> + DBUG_RETURN(trp);
> }
>
>
> @@ -4029,7 +4694,7 @@
> ror_scan->key_rec_length= (param->table->key_info[keynr].key_length +
> param->table->file->ref_length);
> ror_scan->sel_arg= sel_arg;
> - ror_scan->records= param->table->quick_rows[keynr];
> + ror_scan->records= param->quick_rows[keynr];
>
> if (!(bitmap_buf= (my_bitmap_map*) alloc_root(param->mem_root,
> param->fields_bitmap_size)))
> @@ -4049,7 +4714,7 @@
> bitmap_set_bit(&ror_scan->covered_fields, key_part->fieldnr-1);
> }
> ror_scan->index_read_cost=
> - get_index_only_read_time(param, param->table->quick_rows[ror_scan->keynr],
> + get_index_only_read_time(param, param->quick_rows[ror_scan->keynr],
> ror_scan->keynr);
> DBUG_RETURN(ror_scan);
> }
> @@ -4335,7 +5000,7 @@
> }
> if (!prev_covered)
> {
> - double tmp= rows2double(info->param->table->quick_rows[scan->keynr]) /
> + double tmp= rows2double(info->param->quick_rows[scan->keynr]) /
> rows2double(prev_records);
> DBUG_PRINT("info", ("Selectivity multiplier: %g", tmp));
> selectivity_mult *= tmp;
> @@ -4414,7 +5079,7 @@
> }
> else
> {
> - info->index_records += info->param->table->quick_rows[ror_scan->keynr];
> + info->index_records += info->param->quick_rows[ror_scan->keynr];
> info->index_scan_costs += ror_scan->index_read_cost;
> bitmap_union(&info->covered_fields, &ror_scan->covered_fields);
> if (!info->is_covering && bitmap_is_subset(&info->param->needed_fields,
> @@ -6044,13 +6709,138 @@
> return root;
> }
>
> -#define CLONE_KEY1_MAYBE 1
> -#define CLONE_KEY2_MAYBE 2
> -#define swap_clone_flag(A) ((A & 1) << 1) | ((A & 2) >> 1)
>
> +/*
> + Build a range tree for the conjunction of the range parts of two trees
> +
> + SYNOPSIS
> + and_range_trees()
> + param Context info for the operation
> + tree1 SEL_TREE for the first conjunct
> + tree2 SEL_TREE for the second conjunct
> + result SEL_TREE for the result
>
> -static SEL_TREE *
> -tree_and(RANGE_OPT_PARAM *param,SEL_TREE *tree1,SEL_TREE *tree2)
> + DESCRIPTION
> + This function takes range parts of two trees tree1 and tree2 and builds
> + a range tree for the conjunction of the formulas that these two range parts
> + represent.
> + More exactly:
> + if the range part of tree1 represents the normalized formula
> + R1_1 AND ... AND R1_k,
> + and the range part of tree2 represents the normalized formula
> + R2_1 AND ... AND R2_k,
> + then the range part of the result represents the formula:
> + RT = R_1 AND ... AND R_k, where R_i=(R1_i AND R2_i) for each i from [1..k]
> +
> + The function assumes that tree1 is never equal to tree2. At the same
> + time the tree result can be the same as tree1 (but never as tree2).
> + If result==tree1 then rt replaces the range part of tree1 leaving
> + imerges as they are.
> + if result!=tree1 than it is assumed that the SEL_ARG trees in tree1 and
> + tree2 should be preserved. Otherwise they can be destroyed.
> +
> + RETURN
> + 1 if the type the result tree is SEL_TREE::IMPOSSIBLE
> + 0 otherwise
> +*/
> +
> +static
> +int and_range_trees(RANGE_OPT_PARAM *param, SEL_TREE *tree1, SEL_TREE *tree2,
> + SEL_TREE *result)
> +{
> + DBUG_ENTER("and_ranges");
> + key_map result_keys;
> + result_keys.clear_all();
> + key_map anded_keys= tree1->keys_map;
> + anded_keys.merge(tree2->keys_map);
> + int key_no;
> + key_map::Iterator it(anded_keys);
> + while ((key_no= it++) != key_map::Iterator::BITMAP_END)
> + {
> + uint flag=0;
> + SEL_ARG *key1= tree1->keys[key_no];
> + SEL_ARG *key2= tree2->keys[key_no];
> + if (key1 && !key1->simple_key())
> + flag|= CLONE_KEY1_MAYBE;
> + if (key2 && !key2->simple_key())
> + flag|=CLONE_KEY2_MAYBE;
> + if (result != tree1)
> + {
> + if (key1)
> + key1->incr_refs();
> + if (key2)
> + key2->incr_refs();
> + }
> + SEL_ARG *key;
> + if ((result->keys[key_no]= key =key_and(param, key1, key2, flag)))
> + {
> + if (key && key->type == SEL_ARG::IMPOSSIBLE)
> + {
> + result->type= SEL_TREE::IMPOSSIBLE;
> + DBUG_RETURN(1);
> + }
> + result_keys.set_bit(key_no);
> +#ifdef EXTRA_DEBUG
> + if (param->alloced_sel_args < SEL_ARG::MAX_SEL_ARGS)
> + key->test_use_count(key);
> +#endif
> + }
> + }
> + result->keys_map= result_keys;
> + DBUG_RETURN(0);
> +}
> +
> +
> +/*
> + Build a SEL_TREE for a conjunction out of such trees for the conjuncts
> +
> + SYNOPSIS
> + tree_and()
> + param Context info for the operation
> + tree1 SEL_TREE for the first conjunct
> + tree2 SEL_TREE for the second conjunct
> +
> + DESCRIPTION
> + This function builds a tree for the formula (A AND B) out of the trees
> + tree1 and tree2 that has been built for the formulas A and B respectively.
> +
> + In a general case
> + tree1 represents the formula RT1 AND MT1,
> + where RT1 = R1_1 AND ... AND R1_k1, MT1=M1_1 AND ... AND M1_l1;
> + tree2 represents the formula RT2 AND MT2
> + where RT2 = R2_1 AND ... AND R2_k2, MT2=M2_1 and ... and M2_l2.
> +
> + The result tree will represent the formula of the the following structure:
> + RT AND MT1 AND MT2 AND RT1MT2 AND RT2MT1, such that
> + rt is a tree obtained by range intersection of trees tree1 and tree2,
> + RT1MT2 = RT1M2_1 AND ... AND RT1M2_l2,
> + RT2MT1 = RT2M1_1 AND ... AND RT2M1_l1,
> + where rt1m2_i (i=1,...,l2) is the result of the pushdown operation
> + of range tree rt1 into imerge m2_i, while rt2m1_j (j=1,...,l1) is the
> + result of the pushdown operation of range tree rt2 into imerge m1_j.
> +
> + RT1MT2/RT2MT is empty if MT2/MT1 is empty.
> +
> + The range intersection of two range trees is produced by the function
> + and_range_trees. The pushdown of a range tree to a imerge is performed
> + by the function imerge_list_and_tree. This function may produce imerges
> + containing only one range tree. Such trees are intersected with rt and
> + the result of intersection is returned as the range part of the result
> + tree, while the corresponding imerges are removed altogether from its
> + imerge part.
> +
> + NOTE.
> + The pushdown operation of range trees into imerges is needed to be able
> + to construct valid imerges for the condition like this:
> + key1_p1=c1 AND (key1_p2 BETWEEN c21 AND c22 OR key2 < c2)
> +
> + RETURN
> + The result tree, if a success
> + 0 - otherwise.
> +*/
> +
> +static
> +SEL_TREE *tree_and(RANGE_OPT_PARAM *param, SEL_TREE *tree1, SEL_TREE *tree2)
> {
> DBUG_ENTER("tree_and");
> if (!tree1)
> @@ -6072,87 +6862,218 @@
> tree1->type=SEL_TREE::KEY_SMALLER;
> DBUG_RETURN(tree1);
> }
> - key_map result_keys;
> - result_keys.clear_all();
> -
> - /* Join the trees key per key */
> - SEL_ARG **key1,**key2,**end;
> - for (key1= tree1->keys,key2= tree2->keys,end=key1+param->keys ;
> - key1 != end ; key1++,key2++)
> +
> + if (!tree1->merges.is_empty())
> + imerge_list_and_tree(param, &tree1->merges, tree2);
> + if (!tree2->merges.is_empty())
> + imerge_list_and_tree(param, &tree2->merges, tree1);
> + if (and_range_trees(param, tree1, tree2, tree1))
> + DBUG_RETURN(tree1);
> + imerge_list_and_list(&tree1->merges, &tree2->merges);
> + eliminate_single_tree_imerges(param, tree1);
> + DBUG_RETURN(tree1);
> +}
> +
> +
> +/*
> + Eliminate single tree imerges in a SEL_TREE objects
> +
> + SYNOPSIS
> + eliminate_single_tree_imerges()
> + param Context info for the function
> + tree SEL_TREE where single tree imerges are to be eliminated
> +
> + DESCRIPTION
> + For each imerge in 'tree' that contains only one disjunct tree, i.e.
> + for any imerge of the form m=rt, the function performs and operation
> + the range part of tree, replaces rt the with the result of anding and
> + removes imerge m from the the merge part of 'tree'.
> +
> + RETURN VALUE
> + none
> +*/
> +
> +static
> +void eliminate_single_tree_imerges(RANGE_OPT_PARAM *param, SEL_TREE *tree)
> +{
> + SEL_IMERGE *imerge;
> + List<SEL_IMERGE> merges= tree->merges;
> + List_iterator<SEL_IMERGE> it(merges);
> + tree->merges.empty();
> + while ((imerge= it++))
> {
> - uint flag=0;
> - if (*key1 || *key2)
> + if (imerge->trees+1 == imerge->trees_next)
> {
> - if (*key1 && !(*key1)->simple_key())
> - flag|=CLONE_KEY1_MAYBE;
> - if (*key2 && !(*key2)->simple_key())
> - flag|=CLONE_KEY2_MAYBE;
> - *key1=key_and(param, *key1, *key2, flag);
> - if (*key1 && (*key1)->type == SEL_ARG::IMPOSSIBLE)
> - {
> - tree1->type= SEL_TREE::IMPOSSIBLE;
> - DBUG_RETURN(tree1);
> - }
> - result_keys.set_bit(key1 - tree1->keys);
> -#ifdef EXTRA_DEBUG
> - if (*key1 && param->alloced_sel_args < SEL_ARG::MAX_SEL_ARGS)
> - (*key1)->test_use_count(*key1);
> -#endif
> + tree= tree_and(param, tree, *imerge->trees);
> + it.remove();
> }
> }
> - tree1->keys_map= result_keys;
> - /* dispose index_merge if there is a "range" option */
> - if (!result_keys.is_clear_all())
> - {
> - tree1->merges.empty();
> - DBUG_RETURN(tree1);
> - }
> + tree->merges= merges;
> +}
>
> - /* ok, both trees are index_merge trees */
> - imerge_list_and_list(&tree1->merges, &tree2->merges);
> - DBUG_RETURN(tree1);
> +
> +/*
> + For two trees check that there are indexes with ranges in both of them
> +
> + SYNOPSIS
> + sel_trees_have_common_keys()
> + param Context info for the function
This paramemeter doesn't seem to be used, please consider removing it.
> + tree1 SEL_TREE for the first tree
> + tree2 SEL_TREE for the second tree
> + common_keys OUT bitmap of all indexes with ranges in both trees
> +
> + DESCRIPTION
> + For two trees tree1 and tree1 the function checks if there are indexes
> + in their range parts such that SEL_ARG trees are defined for them in the
> + range parts of both trees. The function returns the bitmap of such
> + indexes in the parameter common_keys.
> +
> + RETURN
> + TRUE if there are such indexes (common_keys is nor empty)
> + FALSE otherwise
> +*/
> +
> +static
> +bool sel_trees_have_common_keys(RANGE_OPT_PARAM* param,
> + SEL_TREE *tree1, SEL_TREE *tree2,
> + key_map *common_keys)
> +{
> + *common_keys= tree1->keys_map;
> + common_keys->intersect(tree2->keys_map);
> + return !common_keys->is_clear_all();
> }
>
>
> /*
> - Check if two SEL_TREES can be combined into one (i.e. a single key range
> - read can be constructed for "cond_of_tree1 OR cond_of_tree2" ) without
> - using index_merge.
> + Check whether range parts of two trees can be ored for some indexes
> +
> + SYNOPSIS
> + sel_trees_can_be_ored()
> + param Context info for the function
> + tree1 SEL_TREE for the first tree
> + tree2 SEL_TREE for the second tree
> + common_keys IN/OUT IN: bitmap of all indexes with SEL_ARG in both trees
> + OUT: bitmap of all indexes that can be ored
> +
> + DESCRIPTION
> + For two trees tree1 and tree2 and the bitmap common_keys containing
> + bits for indexes that have SEL_ARG trees in range parts of both trees
> + the function checks if there are indexes for which SEL_ARG trees can
> + be ored. Two SEL_ARG trees for the same index can be ored if the most
> + major components of the index used in these trees coincide. If the
> + SEL_ARG trees for an index cannot be ored the function clears the bit
> + for this index in the bitmap common_keys.
> +
> + The function does not verify that indexes marked in common_keys really
> + have SEL_ARG trees in both tree1 and tree2. It assumes that this is true.
> +
> + NOTE
> + The function sel_trees_can_be_ored is usually used in pair with the
> + function sel_trees_have_common_keys.
> +
> + RETURN
> + TRUE if there are indexes for which SEL_ARG trees can be ored
> + FALSE otherwise
> */
>
> -bool sel_trees_can_be_ored(SEL_TREE *tree1, SEL_TREE *tree2,
> - RANGE_OPT_PARAM* param)
> +static
> +bool sel_trees_can_be_ored(RANGE_OPT_PARAM* param,
> + SEL_TREE *tree1, SEL_TREE *tree2,
> + key_map *common_keys)
> {
> - key_map common_keys= tree1->keys_map;
> DBUG_ENTER("sel_trees_can_be_ored");
> - common_keys.intersect(tree2->keys_map);
> + if (!sel_trees_have_common_keys(param, tree1, tree2, common_keys))
> + DBUG_RETURN(FALSE);
> + int key_no;
> + key_map::Iterator it(*common_keys);
> + while ((key_no= it++) != key_map::Iterator::BITMAP_END)
> + {
> + DBUG_ASSERT(tree1->keys[key_no] && tree2->keys[key_no]);
> + /* Trees have a common key, check if they refer to the same key part */
> + if (tree1->keys[key_no]->part != tree2->keys[key_no]->part)
> + common_keys->clear_bit(key_no);
> + }
> + DBUG_RETURN(!common_keys->is_clear_all());
> +}
> +
> +/*
> + Check whether range parts of two trees must be ored for some indexes
> +
> + SYNOPSIS
> + sel_trees_must_be_ored()
> + param Context info for the function
> + tree1 SEL_TREE for the first tree
> + tree2 SEL_TREE for the second tree
> + ordable_keys bitmap of SEL_ARG trees that can be ored
>
> - if (common_keys.is_clear_all())
> + DESCRIPTION
> + For two trees tree1 and tree2 the function checks whether they must be
> + ored. The function assumes that the bitmap ordable_keys contains bits for
> + those corresponding pairs of SEL_ARG trees from tree1 and tree2 that can
> + be ored.
> + We believe that tree1 and tree2 must be ored if any pair of SEL_ARG trees
> + r1 and r2, such that r1 is from tree1 and r2 is from tree2 and both
> + of them are marked in ordable_keys, can be merged.
> +
> + NOTE
> + The function sel_trees_must_be_ored as a rule is used in pair with the
> + function sel_trees_can_be_ored.
> +
> + RETURN
> + TRUE if there are indexes for which SEL_ARG trees must be ored
> + FALSE otherwise
> +*/
> +
> +static
> +bool sel_trees_must_be_ored(RANGE_OPT_PARAM* param,
> + SEL_TREE *tree1, SEL_TREE *tree2,
> + key_map oredable_keys)
> +{
> + key_map tmp;
> + DBUG_ENTER("sel_trees_must_be_ored");
> +
> + tmp= tree1->keys_map;
> + tmp.merge(tree2->keys_map);
> + tmp.subtract(oredable_keys);
> + if (!tmp.is_clear_all())
> DBUG_RETURN(FALSE);
>
> - /* trees have a common key, check if they refer to same key part */
> - SEL_ARG **key1,**key2;
> - for (uint key_no=0; key_no < param->keys; key_no++)
> - {
> - if (common_keys.is_set(key_no))
> + int idx1, idx2;
> + key_map::Iterator it1(oredable_keys);
> + while ((idx1= it1++) != key_map::Iterator::BITMAP_END)
> + {
> + KEY_PART *key1_init= param->key[idx1]+tree1->keys[idx1]->part;
> + KEY_PART *key1_end= param->key[idx1]+tree1->keys[idx1]->max_part_no;
> + key_map::Iterator it2(oredable_keys);
> + while ((idx2= it2++) != key_map::Iterator::BITMAP_END)
> {
> - key1= tree1->keys + key_no;
> - key2= tree2->keys + key_no;
> - if ((*key1)->part == (*key2)->part)
> - {
> - DBUG_RETURN(TRUE);
> + if (idx2 <= idx1)
> + continue;
> +
> + KEY_PART *key2_init= param->key[idx2]+tree2->keys[idx2]->part;
> + KEY_PART *key2_end= param->key[idx2]+tree2->keys[idx2]->max_part_no;
> + KEY_PART *part1, *part2;
> + for (part1= key1_init, part2= key2_init;
> + part1 < key1_end && part2 < key2_end;
> + part1++, part2++)
> + {
> + if (!part1->field->eq(part2->field))
> + DBUG_RETURN(FALSE);
> }
> }
> }
> - DBUG_RETURN(FALSE);
> -}
> +
> + DBUG_RETURN(TRUE);
> +}
>
>
> /*
> - Remove the trees that are not suitable for record retrieval.
> + Remove the trees that are not suitable for record retrieval
> +
> SYNOPSIS
> - param Range analysis parameter
> - tree Tree to be processed, tree->type is KEY or KEY_SMALLER
> + remove_nonrange_trees()
> + param Context info for the function
> + tree Tree to be processed, tree->type is KEY or KEY_SMALLER
>
> DESCRIPTION
> This function walks through tree->keys[] and removes the SEL_ARG* trees
> @@ -6163,41 +7084,36 @@
>
> A SEL_ARG* tree cannot be used to construct quick select if it has
> tree->part != 0. (e.g. it could represent "keypart2 < const").
> -
> - WHY THIS FUNCTION IS NEEDED
>
> Normally we allow construction of SEL_TREE objects that have SEL_ARG
> - trees that do not allow quick range select construction. For example for
> - " keypart1=1 AND keypart2=2 " the execution will proceed as follows:
> + trees that do not allow quick range select construction.
> + For example:
> + for " keypart1=1 AND keypart2=2 " the execution will proceed as follows:
> tree1= SEL_TREE { SEL_ARG{keypart1=1} }
> tree2= SEL_TREE { SEL_ARG{keypart2=2} } -- can't make quick range select
> from this
> call tree_and(tree1, tree2) -- this joins SEL_ARGs into a usable SEL_ARG
> tree.
> -
> - There is an exception though: when we construct index_merge SEL_TREE,
> - any SEL_ARG* tree that cannot be used to construct quick range select can
> - be removed, because current range analysis code doesn't provide any way
> - that tree could be later combined with another tree.
> - Consider an example: we should not construct
> - st1 = SEL_TREE {
> - merges = SEL_IMERGE {
> - SEL_TREE(t.key1part1 = 1),
> - SEL_TREE(t.key2part2 = 2) -- (*)
> - }
> - };
> - because
> - - (*) cannot be used to construct quick range select,
> - - There is no execution path that would cause (*) to be converted to
> - a tree that could be used.
> -
> - The latter is easy to verify: first, notice that the only way to convert
> - (*) into a usable tree is to call tree_and(something, (*)).
> -
> - Second look at what tree_and/tree_or function would do when passed a
> - SEL_TREE that has the structure like st1 tree has, and conlcude that
> - tree_and(something, (*)) will not be called.
>
> + Another example:
> + tree3= SEL_TREE { SEL_ARG{key1part1 = 1} }
> + tree4= SEL_TREE { SEL_ARG{key2part2 = 2} } -- can't make quick range select
> + from this
> + call tree_or(tree3, tree4) -- creates a SEL_MERGE ot of which no index
> + merge can be constructed, but it is potentially useful, as anding it with
> + tree5= SEL_TREE { SEL_ARG{key2part1 = 3} } creates an index merge that
> + represents the formula
> + key1part1=1 AND key2part1=3 OR key2part1=3 AND key2part2=2
> + for which an index merge can be built.
> +
> + Any final SEL_TREE may contains SEL_ARG trees for which no quick select
s/contains/contain/?
> + can be built. Such SEL_ARG trees should be removed from the range part
> + before different range scans are evaluated. Such SEL_ARG trees also should
> + be removed from all range trees of each index merge before different
> + possible index merge plans are evaluated. If after this removal one
> + of the range trees in the index merge becomes empty the whole index merge
> + must be discarded.
> +
> RETURN
> 0 Ok, some suitable trees left
> 1 No tree->keys[] left.
> @@ -6223,6 +7139,74 @@
> }
>
>
> +/*
> + Build a SEL_TREE for a disjunction out of such trees for the disjuncts
> +
> + SYNOPSIS
> + tree_or()
> + param Context info for the operation
> + tree1 SEL_TREE for the first disjunct
> + tree2 SEL_TREE for the second disjunct
> +
> + DESCRIPTION
> + This function builds a tree for the formula (A OR B) out of the trees
> + tree1 and tree2 that has been built for the formulas A and B respectively.
> +
> + In a general case
> + tree1 represents the formula RT1 AND MT1,
> + where RT1=R1_1 AND ... AND R1_k1, MT1=M1_1 AND ... AND M1_l1;
> + tree2 represents the formula RT2 AND MT2
> + where RT2=R2_1 AND ... AND R2_k2, MT2=M2_1 and ... and M2_l2.
> +
> + The function constructs the result tree according the formula
> + (RT1 OR RT2) AND (MT1 OR RT1) AND (MT2 OR RT2) AND (MT1 OR MT2)
> + that is equivalent to the formula (RT1 AND MT1) OR (RT2 AND MT2).
> +
> + To limit the number of produced imerges the function considers
> + a weaker formula than the original one:
> + (RT1 AND M1_1) OR (RT2 AND M2_1)
> + that is equivalent to:
> + (RT1 OR RT2) (1)
> + AND
> + (M1_1 OR M2_1) (2)
> + AND
> + (M1_1 OR RT2) (3)
> + AND
> + (M2_1 OR RT1) (4)
> +
> + For the first conjunct (1) the function builds a tree with a range part
> + and, possibly, one imerge. For the other conjuncts (2-4)the function
> + produces sets of imerges. All constructed imerges are included into the
> + result tree.
> +
> + For the formula (1) the function produces the tree representing a formula
> + of the structure RT [AND M], such that:
> + - the range tree rt contains the result of oring SEL_ARG trees from rt1
> + and rt2
> + - the imerge m consists of two range trees rt1 and rt2.
> + The imerge m is added if it's not true that rt1 and rt2 must be ored
> + If rt1 and rt2 can't be ored rt is empty and only m is produced for (1).
> +
> + To produce imerges for the formula (2) the function calls the function
> + imerge_list_or_list passing it the merge parts of tree1 and tree2 as
> + parameters.
> +
> + To produce imerges for the formula (3) the function calls the function
> + imerge_list_or_tree passing it the imerge m1_1 and the range tree rt2 as
> + parameters. Similarly, to produce imerges for the formula (4) the function
> + calls the function imerge_list_or_tree passing it the imerge m2_1 and the
> + range tree rt1.
> +
> + If rt1 is empty then the trees for (1) and (4) are empty.
> + If rt2 is empty then the trees for (1) and (3) are empty.
> + If mt1 is empty then the trees for (2) and (3) are empty.
> + If mt2 is empty then the trees for (2) and (4) are empty.
> +
> + RETURN
> + The result tree for the operation if a success
> + 0 - otherwise
> +*/
> +
> static SEL_TREE *
> tree_or(RANGE_OPT_PARAM *param,SEL_TREE *tree1,SEL_TREE *tree2)
> {
> @@ -6238,74 +7222,100 @@
> if (tree2->type == SEL_TREE::MAYBE)
> DBUG_RETURN(tree2);
>
> - SEL_TREE *result= 0;
> - key_map result_keys;
> - result_keys.clear_all();
> - if (sel_trees_can_be_ored(tree1, tree2, param))
> + SEL_TREE *result= NULL;
> + key_map result_keys;
> + key_map ored_keys;
> + SEL_TREE *rtree[2]= {NULL,NULL};
> + SEL_IMERGE *imerge[2]= {NULL, NULL};
> + bool no_ranges1= tree1->without_ranges();
This variable is only used negated, "!no_ranges".
Double negation makes the code very hard to read. Could you please change to
positive notation? (the same goes for without_ranges() and without_imerges())?
> + bool no_ranges2= tree2->without_ranges();
> + bool no_merges1= tree1->without_imerges();
> + bool no_merges2= tree2->without_imerges();
> + if (!no_ranges1 && !no_merges2)
> + {
> + rtree[0]= new SEL_TREE(tree1, TRUE, param);
> + imerge[1]= new SEL_IMERGE(tree2->merges.head(), 0, param);
> + }
> + if (!no_ranges2 && !no_merges1)
> {
> - /* Join the trees key per key */
> - SEL_ARG **key1,**key2,**end;
> - for (key1= tree1->keys,key2= tree2->keys,end= key1+param->keys ;
> - key1 != end ; key1++,key2++)
> - {
> - *key1=key_or(param, *key1, *key2);
> - if (*key1)
> + rtree[1]= new SEL_TREE(tree2, TRUE, param);
> + imerge[0]= new SEL_IMERGE(tree1->merges.head(), 0, param);
> + }
> + bool no_imerge_from_ranges= FALSE;
> + if (!(result= new SEL_TREE()))
> + DBUG_RETURN(result);
> +
> + /* Build the range part of the tree for the formula (1) */
> + if (sel_trees_can_be_ored(param, tree1, tree2, &ored_keys))
> + {
> + bool must_be_ored= sel_trees_must_be_ored(param, tree1, tree2, ored_keys);
> + no_imerge_from_ranges= must_be_ored;
> + key_map::Iterator it(ored_keys);
> + int key_no;
> + while ((key_no= it++) != key_map::Iterator::BITMAP_END)
> + {
> + SEL_ARG *key1= tree1->keys[key_no];
> + SEL_ARG *key2= tree2->keys[key_no];
> + if (!must_be_ored)
> {
> - result=tree1; // Added to tree1
> - result_keys.set_bit(key1 - tree1->keys);
> -#ifdef EXTRA_DEBUG
> - if (param->alloced_sel_args < SEL_ARG::MAX_SEL_ARGS)
> - (*key1)->test_use_count(*key1);
> -#endif
> + key1->incr_refs();
> + key2->incr_refs();
> }
> + if ((result->keys[key_no]= key_or(param, key1, key2)))
> + result->keys_map.set_bit(key_no);
> }
> - if (result)
> - result->keys_map= result_keys;
> + result->type= tree1->type;
> }
> - else
> +
> + if (no_imerge_from_ranges && no_merges1 && no_merges2)
> {
> - /* ok, two trees have KEY type but cannot be used without index merge */
> - if (tree1->merges.is_empty() && tree2->merges.is_empty())
> - {
> - if (param->remove_jump_scans)
> - {
> - bool no_trees= remove_nonrange_trees(param, tree1);
> - no_trees= no_trees || remove_nonrange_trees(param, tree2);
> - if (no_trees)
> - DBUG_RETURN(new SEL_TREE(SEL_TREE::ALWAYS));
> - }
> - SEL_IMERGE *merge;
> - /* both trees are "range" trees, produce new index merge structure */
> - if (!(result= new SEL_TREE()) || !(merge= new SEL_IMERGE()) ||
> - (result->merges.push_back(merge)) ||
> - (merge->or_sel_tree(param, tree1)) ||
> - (merge->or_sel_tree(param, tree2)))
> + if (result->keys_map.is_clear_all())
> + result->type= SEL_TREE::ALWAYS;
> + DBUG_RETURN(result);
> + }
> +
> + SEL_IMERGE *imerge_from_ranges;
> + if (!(imerge_from_ranges= new SEL_IMERGE()))
> + result= NULL;
> + else if (!no_ranges1 && !no_ranges2 && !no_imerge_from_ranges)
> + {
> + /* Build the imerge part of the tree for the formula (1) */
> + SEL_TREE *rt1= tree1;
> + SEL_TREE *rt2= tree2;
> + if (!no_merges1)
> + rt1= new SEL_TREE(tree1, TRUE, param);
> + if (!no_merges2)
> + rt2= new SEL_TREE(tree2, TRUE, param);
> + if (!rt1 || !rt2 ||
> + result->merges.push_back(imerge_from_ranges) ||
> + imerge_from_ranges->or_sel_tree(param, rt1) ||
> + imerge_from_ranges->or_sel_tree(param, rt2))
> result= NULL;
^^^^^^
Wrong identation
> - else
> - result->type= tree1->type;
> - }
> - else if (!tree1->merges.is_empty() && !tree2->merges.is_empty())
> - {
> - if (imerge_list_or_list(param, &tree1->merges, &tree2->merges))
> - result= new SEL_TREE(SEL_TREE::ALWAYS);
> - else
> - result= tree1;
> - }
> - else
> - {
> - /* one tree is index merge tree and another is range tree */
> - if (tree1->merges.is_empty())
> - swap_variables(SEL_TREE*, tree1, tree2);
> -
> - if (param->remove_jump_scans && remove_nonrange_trees(param, tree2))
> - DBUG_RETURN(new SEL_TREE(SEL_TREE::ALWAYS));
> - /* add tree2 to tree1->merges, checking if it collapses to ALWAYS */
> - if (imerge_list_or_tree(param, &tree1->merges, tree2))
> - result= new SEL_TREE(SEL_TREE::ALWAYS);
> - else
> - result= tree1;
> - }
> }
> + if (!result)
> + DBUG_RETURN(result);
> +
> + result->type= tree1->type;
> +
> + if (!no_merges1 && !no_merges2 &&
> + !imerge_list_or_list(param, &tree1->merges, &tree2->merges))
> + {
> + /* Build the imerges for the formula (2) */
> + imerge_list_and_list(&result->merges, &tree1->merges);
> + }
> +
> + /* Build the imerges for the formulas (3) and (4) */
> + for (uint i=0; i < 2; i++)
> + {
> + List<SEL_IMERGE> merges;
> + SEL_TREE *rt= rtree[i];
> + SEL_IMERGE *im= imerge[1-i];
> +
> + if (rt && im && !merges.push_back(im) &&
> + !imerge_list_or_tree(param, &merges, rt))
> + imerge_list_and_list(&result->merges, &merges);
> + }
> +
> DBUG_RETURN(result);
> }
>
> @@ -6351,6 +7361,7 @@
> if (!key1)
> return &null_element; // Impossible ranges
> key1->use_count++;
> + key1->max_part_no= max(key2->max_part_no, key2->part+1);
> return key1;
> }
>
> @@ -6450,6 +7461,7 @@
> key1->use_count--;
> key2->use_count--;
> SEL_ARG *e1=key1->first(), *e2=key2->first(), *new_tree=0;
> + uint max_part_no= max(key1->max_part_no, key2->max_part_no);
>
> while (e1 && e2)
> {
> @@ -6487,6 +7499,7 @@
> key2->free_tree();
> if (!new_tree)
> return &null_element; // Impossible range
> + new_tree->max_part_no= max_part_no;
> return new_tree;
> }
>
> @@ -6558,7 +7571,7 @@
> {
> swap_variables(SEL_ARG *,key1,key2);
> }
> - if (key1->use_count > 0 || !(key1=key1->clone_tree(param)))
> + if (key1->use_count > 0 && !(key1=key1->clone_tree(param)))
> return 0; // OOM
> }
>
> @@ -6566,6 +7579,8 @@
> bool key2_shared=key2->use_count != 0;
> key1->maybe_flag|=key2->maybe_flag;
>
> + uint max_part_no= max(key1->max_part_no, key2->max_part_no);
> +
> for (key2=key2->first(); key2; )
> {
> SEL_ARG *tmp=key1->find_range(key2); // Find key1.min <= key2.min
> @@ -6758,6 +7773,7 @@
> key2=next;
> }
> key1->use_count++;
> + key1->max_part_no= max_part_no;
Is it intentional that here in key_or() max_part_no calculation is so
imprecise? One can construct many cases where the result of key_or()'s
will have
result->max_part_no < max(key1->max_part_no, key2->max_part_no);
e.g. consider
key_or(keypart1=c1, (keypart1=c1 AND keypart2=c2))
I think it's fairly easy to have this function to save the real max_part_no?
(if we don't want to do that, we need a comment near max_part_no's definition
about that it is an upper bound, and a couple of sentences in this function
that would explain why we chose not to calculate real max_part_no).
> return key1;
> }
>
> @@ -7237,11 +8253,7 @@
> void SEL_ARG::test_use_count(SEL_ARG *root)
> {
> uint e_count=0;
> - if (this == root && use_count != 1)
> - {
> - sql_print_information("Use_count: Wrong count %lu for root",use_count);
> - return;
> - }
> +
> if (this->type != SEL_ARG::KEY_RANGE)
> return;
> for (SEL_ARG *pos=first(); pos ; pos=pos->next)
> @@ -7344,12 +8356,13 @@
> param->table->quick_n_ranges[key]= param->n_ranges;
> param->table->quick_condition_rows=
> min(param->table->quick_condition_rows, records);
> + param->table->quick_rows[key]= records;
> }
> /*
> Need to save quick_rows in any case as it is used when calculating
> cost of ROR intersection:
> */
> - param->table->quick_rows[key]=records;
> + param->quick_rows[key]= records;
> if (cpk_scan)
> param->is_ror_scan= TRUE;
> }
> diff -urN --exclude='.*' maria-5.1-wl24-clean2/sql/sql_list.h maria-5.1-wl24-nocompile/sql/sql_list.h
> --- maria-5.1-wl24-clean2/sql/sql_list.h 2009-11-03 00:18:22.000000000 +0300
> +++ maria-5.1-wl24-nocompile/sql/sql_list.h 2009-11-03 00:11:54.000000000 +0300
> @@ -168,6 +168,14 @@
> {
> if (!list->is_empty())
> {
> +#if 0
> +#else
> + if (is_empty())
> + {
> + *this= *list;
> + return;
> + }
> +#endif
Please remove #if/#else.
> *last= list->first;
> last= list->last;
> elements+= list->elements;
BR
Sergey
--
Sergey Petrunia, Software Developer
Monty Program AB, http://askmonty.org
Blog: http://s.petrunia.net/blog
