pars0opt.c

这是linux下运行的mysql软件包,可用于linux 下安装 php + mysql + apach 的网络配置

	ut_a(UT_LIST_GET_LEN(plan->end_conds) >= plan->n_exact_match);
}

/***********************************************************************
Looks for occurrences of the columns of the table in the query subgraph and
adds them to the list of columns if an occurrence of the same column does not
already exist in the list. If the column is already in the list, puts a value
indirection to point to the occurrence in the column list, except if the
column occurrence we are looking at is in the column list, in which case
nothing is done. */

void
opt_find_all_cols(
/*==============*/
	ibool		copy_val,	/* in: if TRUE, new found columns are
					added as columns to copy */
	dict_index_t*	index,		/* in: index of the table to use */
	sym_node_list_t* col_list,	/* in: base node of a list where
					to add new found columns */
	plan_t*		plan,		/* in: plan or NULL */
	que_node_t*	exp)		/* in: expression or condition or
					NULL */
{
	func_node_t*	func_node;
	que_node_t*	arg;
	sym_node_t*	sym_node;
	sym_node_t*	col_node;
	ulint		col_pos;

	if (exp == NULL) {

		return;
	}
	
	if (que_node_get_type(exp) == QUE_NODE_FUNC) {
		func_node = exp;

		arg = func_node->args;

		while (arg) {
			opt_find_all_cols(copy_val, index, col_list, plan,
									arg);
			arg = que_node_get_next(arg);
		}

		return;
	}

	ut_a(que_node_get_type(exp) == QUE_NODE_SYMBOL);

	sym_node = exp;

	if (sym_node->token_type != SYM_COLUMN) {

		return;
	}

	if (sym_node->table != index->table) {

		return;
	}

	/* Look for an occurrence of the same column in the plan column
	list */

	col_node = UT_LIST_GET_FIRST(*col_list);

	while (col_node) {
		if (col_node->col_no == sym_node->col_no) {

			if (col_node == sym_node) {
				/* sym_node was already in a list: do
				nothing */

				return;
			}

			/* Put an indirection */
			sym_node->indirection = col_node;
			sym_node->alias = col_node;

			return;
		}

		col_node = UT_LIST_GET_NEXT(col_var_list, col_node);
	}

	/* The same column did not occur in the list: add it */

	UT_LIST_ADD_LAST(col_var_list, *col_list, sym_node);

	sym_node->copy_val = copy_val;

	/* Fill in the field_no fields in sym_node */
	
	sym_node->field_nos[SYM_CLUST_FIELD_NO]
				= dict_index_get_nth_col_pos(
				dict_table_get_first_index(index->table),
							sym_node->col_no);
	if (!(index->type & DICT_CLUSTERED)) {	

		ut_a(plan);

		col_pos = dict_index_get_nth_col_pos(index, sym_node->col_no);

		if (col_pos == ULINT_UNDEFINED) {

			plan->must_get_clust = TRUE;
		}
		
		sym_node->field_nos[SYM_SEC_FIELD_NO] = col_pos;
	}
}

/***********************************************************************
Looks for occurrences of the columns of the table in conditions which are
not yet determined AFTER the join operation has fetched a row in the ith
table. The values for these column must be copied to dynamic memory for
later use. */
static
void
opt_find_copy_cols(
/*===============*/
	sel_node_t*	sel_node,	/* in: select node */
	ulint		i,		/* in: ith table in the join */
	func_node_t*	search_cond)	/* in: search condition or NULL */
{
	func_node_t*	new_cond;
	plan_t*		plan;

	if (search_cond == NULL) {

		return;
	}
	
	ut_ad(que_node_get_type(search_cond) == QUE_NODE_FUNC);

	if (search_cond->func == PARS_AND_TOKEN) {
		new_cond = search_cond->args;

		opt_find_copy_cols(sel_node, i, new_cond);
		
		new_cond = que_node_get_next(new_cond);
		
		opt_find_copy_cols(sel_node, i, new_cond);

		return;
	}

	if (!opt_check_exp_determined_before(search_cond, sel_node, i + 1)) {

		/* Any ith table columns occurring in search_cond should be
		copied, as this condition cannot be tested already on the
		fetch from the ith table */

		plan = sel_node_get_nth_plan(sel_node, i);
		
		opt_find_all_cols(TRUE, plan->index, &(plan->columns), plan,
								search_cond);
	}
}

/***********************************************************************
Classifies the table columns according to whether we use the column only while
holding the latch on the page, or whether we have to copy the column value to
dynamic memory. Puts the first occurrence of a column to either list in the
plan node, and puts indirections to later occurrences of the column. */
static
void
opt_classify_cols(
/*==============*/
	sel_node_t*	sel_node,	/* in: select node */
	ulint		i)		/* in: ith table in the join */
{
	plan_t*		plan;
	que_node_t*	exp;

	plan = sel_node_get_nth_plan(sel_node, i);

	/* The final value of the following field will depend on the
	environment of the select statement: */

	plan->must_get_clust = FALSE;

	UT_LIST_INIT(plan->columns);

	/* All select list columns should be copied: therefore TRUE as the
	first argument */

	exp = sel_node->select_list;

	while (exp) {
		opt_find_all_cols(TRUE, plan->index, &(plan->columns), plan,
									exp);
		exp = que_node_get_next(exp);
	}

	opt_find_copy_cols(sel_node, i, sel_node->search_cond);

	/* All remaining columns in the search condition are temporary
	columns: therefore FALSE */
	
	opt_find_all_cols(FALSE, plan->index, &(plan->columns), plan,
						sel_node->search_cond);
}

/***********************************************************************
Fills in the info in plan which is used in accessing a clustered index
record. The columns must already be classified for the plan node. */
static
void
opt_clust_access(
/*=============*/
	sel_node_t*	sel_node,	/* in: select node */
	ulint		n)		/* in: nth table in select */
{
	plan_t*		plan;
	dict_table_t*	table;
	dict_index_t*	clust_index;
	dict_index_t*	index;
	dfield_t*	dfield;
	mem_heap_t*	heap;
	ulint		n_fields;
	ulint		pos;
	ulint		i;

	plan = sel_node_get_nth_plan(sel_node, n);

	index = plan->index;
	
	/* The final value of the following field depends on the environment
	of the select statement: */
		
	plan->no_prefetch = FALSE;

	if (index->type & DICT_CLUSTERED) {
		plan->clust_map = NULL;
		plan->clust_ref = NULL;

		return;
	}

	table = index->table;

	clust_index = dict_table_get_first_index(table);

	n_fields = dict_index_get_n_unique(clust_index);

	heap = pars_sym_tab_global->heap;

	plan->clust_ref = dtuple_create(heap, n_fields);

	dict_index_copy_types(plan->clust_ref, clust_index, n_fields);
	
	plan->clust_map = mem_heap_alloc(heap, n_fields * sizeof(ulint));
	
	for (i = 0; i < n_fields; i++) {
		pos = dict_index_get_nth_field_pos(index, clust_index, i);

		ut_a(pos != ULINT_UNDEFINED);

		/* We optimize here only queries to InnoDB's internal system
		tables, and they should not contain column prefix indexes. */

		if (dict_index_get_nth_field(index, pos)->prefix_len != 0
		    || dict_index_get_nth_field(clust_index, i)
							->prefix_len != 0) {
			fprintf(stderr,
"InnoDB: Error in pars0opt.c: table %s has prefix_len != 0\n",
				index->table_name);
		}

		*(plan->clust_map + i) = pos;

		ut_ad((pos != ULINT_UNDEFINED)
			|| ((table->type == DICT_TABLE_CLUSTER_MEMBER)
				 		&& (i == table->mix_len)));
	}

	if (table->type == DICT_TABLE_CLUSTER_MEMBER) {
		
		/* Preset the mix id field to the mix id constant */
		
		dfield = dtuple_get_nth_field(plan->clust_ref, table->mix_len);
		
		dfield_set_data(dfield, mem_heap_alloc(heap,
							table->mix_id_len),
							table->mix_id_len);
		ut_memcpy(dfield_get_data(dfield), table->mix_id_buf,
							table->mix_id_len);
	}
}

/***********************************************************************
Optimizes a select. Decides which indexes to tables to use. The tables
are accessed in the order that they were written to the FROM part in the
select statement. */

void
opt_search_plan(
/*============*/
	sel_node_t*	sel_node)	/* in: parsed select node */
{
	sym_node_t*	table_node;
	dict_table_t*	table;
	order_node_t*	order_by;
	ulint		i;
	
	sel_node->plans = mem_heap_alloc(pars_sym_tab_global->heap,
					sel_node->n_tables * sizeof(plan_t));

	/* Analyze the search condition to find out what we know at each
	join stage about the conditions that the columns of a table should
	satisfy */

	table_node = sel_node->table_list;

	if (sel_node->order_by == NULL) {
		sel_node->asc = TRUE;
	} else {
		order_by = sel_node->order_by;

		sel_node->asc = order_by->asc;
	}
	
	for (i = 0; i < sel_node->n_tables; i++) {

		table = table_node->table;

		/* Choose index through which to access the table */
	
		opt_search_plan_for_table(sel_node, i, table);

		/* Determine the search condition conjuncts we can test at
		this table; normalize the end conditions */
	
		opt_determine_and_normalize_test_conds(sel_node, i);

		table_node = que_node_get_next(table_node);
	}

	table_node = sel_node->table_list;

	for (i = 0; i < sel_node->n_tables; i++) {

		/* Classify the table columns into those we only need to access
		but not copy, and to those we must copy to dynamic memory */

		opt_classify_cols(sel_node, i);

		/* Calculate possible info for accessing the clustered index
		record */

		opt_clust_access(sel_node, i);

		table_node = que_node_get_next(table_node);
	}
	
	/* Check that the plan obeys a possible order-by clause: if not,
	an assertion error occurs */
	
	opt_check_order_by(sel_node);

#ifdef UNIV_SQL_DEBUG
	opt_print_query_plan(sel_node);
#endif
}

/************************************************************************
Prints info of a query plan. */

void
opt_print_query_plan(
/*=================*/
	sel_node_t*	sel_node)	/* in: select node */
{
	plan_t*	plan;
	ulint	n_fields;
	ulint	i;

	fputs("QUERY PLAN FOR A SELECT NODE\n", stderr);

	fputs(sel_node->asc ? "Asc. search; " : "Desc. search; ", stderr);

	if (sel_node->set_x_locks) {
		fputs("sets row x-locks; ", stderr);
		ut_a(sel_node->row_lock_mode == LOCK_X);
		ut_a(!sel_node->consistent_read);
	} else if (sel_node->consistent_read) {
		fputs("consistent read; ", stderr);
	} else {
		ut_a(sel_node->row_lock_mode == LOCK_S);
		fputs("sets row s-locks; ", stderr);
	}

	putc('\n', stderr);

	for (i = 0; i < sel_node->n_tables; i++) {
		plan = sel_node_get_nth_plan(sel_node, i);

		if (plan->tuple) {
			n_fields = dtuple_get_n_fields(plan->tuple);
		} else {
			n_fields = 0;
		}

		fputs("Table ", stderr);
		dict_index_name_print(stderr, NULL, plan->index);
		fprintf(stderr,"; exact m. %lu, match %lu, end conds %lu\n",
		        (unsigned long) plan->n_exact_match,
		        (unsigned long) n_fields,
			(unsigned long) UT_LIST_GET_LEN(plan->end_conds));
	}
}