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

/******************************************************
Simple SQL optimizer

(c) 1997 Innobase Oy

Created 12/21/1997 Heikki Tuuri
*******************************************************/

#include "pars0opt.h"

#ifdef UNIV_NONINL
#include "pars0opt.ic"
#endif

#include "row0sel.h"
#include "row0ins.h"
#include "row0upd.h"
#include "dict0dict.h"
#include "dict0mem.h"
#include "que0que.h"
#include "pars0grm.h"
#include "pars0pars.h"
#include "lock0lock.h"

#define OPT_EQUAL	1	/* comparison by = */
#define OPT_COMPARISON	2	/* comparison by <, >, <=, or >= */

#define OPT_NOT_COND	1
#define OPT_END_COND	2
#define OPT_TEST_COND	3
#define OPT_SCROLL_COND	4


/***********************************************************************
Inverts a comparison operator. */
static
int
opt_invert_cmp_op(
/*==============*/
			/* out: the equivalent operator when the order of
			the arguments is switched */
	int	op)	/* in: operator */
{
	if (op == '<') {
		return('>');
	} else if (op == '>') {
		return('<');
	} else if (op == '=') {
		return('=');
	} else if (op == PARS_LE_TOKEN) {
		return(PARS_GE_TOKEN);
	} else if (op == PARS_GE_TOKEN) {
		return(PARS_LE_TOKEN);
	} else {
		ut_error;
	}

	return(0);
}

/***********************************************************************
Checks if the value of an expression can be calculated BEFORE the nth table
in a join is accessed. If this is the case, it can possibly be used in an
index search for the nth table. */
static
ibool
opt_check_exp_determined_before(
/*============================*/
					/* out: TRUE if already determined */
	que_node_t*	exp,		/* in: expression */
	sel_node_t*	sel_node,	/* in: select node */
	ulint		nth_table)	/* in: nth table will be accessed */
{
	func_node_t*	func_node;
	sym_node_t*	sym_node;
	dict_table_t*	table;
	que_node_t*	arg;
	ulint		i;

	ut_ad(exp && sel_node);

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

		arg = func_node->args;

		while (arg) {
			if (!opt_check_exp_determined_before(arg, sel_node,
								nth_table)) {
				return(FALSE);
			}

			arg = que_node_get_next(arg);
		}

		return(TRUE);
	}

	ut_a(que_node_get_type(exp) == QUE_NODE_SYMBOL);

	sym_node = exp;

	if (sym_node->token_type != SYM_COLUMN) {

		return(TRUE);
	}

	for (i = 0; i < nth_table; i++) {
	
		table = sel_node_get_nth_plan(sel_node, i)->table;

		if (sym_node->table == table) {

			return(TRUE);
		}
	}

	return(FALSE);	
}

/***********************************************************************
Looks in a comparison condition if a column value is already restricted by
it BEFORE the nth table is accessed. */
static
que_node_t*
opt_look_for_col_in_comparison_before(
/*==================================*/
					/* out: expression restricting the
					value of the column, or NULL if not
					known */
	ulint		cmp_type,	/* in: OPT_EQUAL, OPT_COMPARISON */
	ulint		col_no,		/* in: column number */
	func_node_t*	search_cond,	/* in: comparison condition */
	sel_node_t*	sel_node,	/* in: select node */
	ulint		nth_table,	/* in: nth table in a join (a query
					from a single table is considered a
					join of 1 table) */
	ulint*		op)		/* out: comparison operator ('=',
					PARS_GE_TOKEN, ... ); this is inverted
					if the column appears on the right
					side */
{
	sym_node_t*	sym_node;
	dict_table_t*	table;
	que_node_t*	exp;
	que_node_t*	arg;

	ut_ad(search_cond);

	ut_a((search_cond->func == '<')
	     || (search_cond->func == '>')		
	     || (search_cond->func == '=')		
	     || (search_cond->func == PARS_GE_TOKEN)
	     || (search_cond->func == PARS_LE_TOKEN));

	table = sel_node_get_nth_plan(sel_node, nth_table)->table;

	if ((cmp_type == OPT_EQUAL) && (search_cond->func != '=')) {

		return(NULL);

	} else if ((cmp_type == OPT_COMPARISON)
			&& (search_cond->func != '<')
			&& (search_cond->func != '>')			
			&& (search_cond->func != PARS_GE_TOKEN)
			&& (search_cond->func != PARS_LE_TOKEN)) {

		return(NULL);
	}

	arg = search_cond->args;

	if (que_node_get_type(arg) == QUE_NODE_SYMBOL) {
		sym_node = arg;

		if ((sym_node->token_type == SYM_COLUMN)
				&& (sym_node->table == table)
				&& (sym_node->col_no == col_no)) {
				
			/* sym_node contains the desired column id */

			/* Check if the expression on the right side of the
			operator is already determined */

			exp = que_node_get_next(arg);
				
			if (opt_check_exp_determined_before(exp, sel_node,
								nth_table)) {
				*op = search_cond->func;

				return(exp);
			}
		}
    	}

    	exp = search_cond->args;
        arg = que_node_get_next(arg);

	if (que_node_get_type(arg) == QUE_NODE_SYMBOL) {
		sym_node = arg;

		if ((sym_node->token_type == SYM_COLUMN)
				&& (sym_node->table == table)
				&& (sym_node->col_no == col_no)) {
				
			if (opt_check_exp_determined_before(exp, sel_node,
								nth_table)) {
				*op = opt_invert_cmp_op(search_cond->func);

				return(exp);
			}
		}
    	}
	
	return(NULL);
}

/***********************************************************************
Looks in a search condition if a column value is already restricted by the
search condition BEFORE the nth table is accessed. Takes into account that
if we will fetch in an ascending order, we cannot utilize an upper limit for
a column value; in a descending order, respectively, a lower limit. */
static
que_node_t*
opt_look_for_col_in_cond_before(
/*============================*/
					/* out: expression restricting the
					value of the column, or NULL if not
					known */
	ulint		cmp_type,	/* in: OPT_EQUAL, OPT_COMPARISON */
	ulint		col_no,		/* in: column number */
	func_node_t*	search_cond,	/* in: search condition or NULL */
	sel_node_t*	sel_node,	/* in: select node */
	ulint		nth_table,	/* in: nth table in a join (a query
					from a single table is considered a
					join of 1 table) */
	ulint*		op)		/* out: comparison operator ('=',
					PARS_GE_TOKEN, ... ) */
{
	func_node_t*	new_cond;
	que_node_t*	exp;

	if (search_cond == NULL) {

		return(NULL);
	}		

	ut_a(que_node_get_type(search_cond) == QUE_NODE_FUNC);
	ut_a(search_cond->func != PARS_OR_TOKEN);
	ut_a(search_cond->func != PARS_NOT_TOKEN);	
	
	if (search_cond->func == PARS_AND_TOKEN) {
		new_cond = search_cond->args;

		exp = opt_look_for_col_in_cond_before(cmp_type, col_no,
					new_cond, sel_node, nth_table, op);
		if (exp) {

			return(exp);
		}

		new_cond = que_node_get_next(new_cond);
		
		exp = opt_look_for_col_in_cond_before(cmp_type, col_no,
					new_cond, sel_node, nth_table, op);
		return(exp);
	}

	exp = opt_look_for_col_in_comparison_before(cmp_type, col_no,
					search_cond, sel_node, nth_table, op);
	if (exp == NULL) {

		return(NULL);
	}

	/* If we will fetch in an ascending order, we cannot utilize an upper
	limit for a column value; in a descending order, respectively, a lower
	limit */
	
	if (sel_node->asc && ((*op == '<') || (*op == PARS_LE_TOKEN))) {

		return(NULL);

	} else if (!sel_node->asc && ((*op == '>') || (*op == PARS_GE_TOKEN))) {

		return(NULL);
	}

	return(exp);
}

/***********************************************************************
Calculates the goodness for an index according to a select node. The
goodness is 4 times the number of first fields in index whose values we
already know exactly in the query. If we have a comparison condition for
an additional field, 2 point are added. If the index is unique, and we know
all the unique fields for the index we add 1024 points. For a clustered index
we add 1 point. */
static
ulint
opt_calc_index_goodness(
/*====================*/
					/* out: goodness */
	dict_index_t*	index,		/* in: index */
	sel_node_t*	sel_node,	/* in: parsed select node */
	ulint		nth_table,	/* in: nth table in a join */
	que_node_t**	index_plan,	/* in/out: comparison expressions for
					this index */
	ulint*		last_op)	/* out: last comparison operator, if
					goodness > 1 */
{
	que_node_t*	exp;
	ulint		goodness;
	ulint		n_fields;
	ulint		col_no;
	ulint		mix_id_col_no;
	ulint		op;
	ulint		j;

	goodness = 0;

	/* Note that as higher level node pointers in the B-tree contain
	page addresses as the last field, we must not put more fields in
	the search tuple than dict_index_get_n_unique_in_tree(index); see
	the note in btr_cur_search_to_nth_level. */
	
	n_fields = dict_index_get_n_unique_in_tree(index);

	mix_id_col_no = dict_table_get_sys_col_no(index->table, DATA_MIX_ID);
	
	for (j = 0; j < n_fields; j++) {

		col_no = dict_index_get_nth_col_no(index, j);

		exp = opt_look_for_col_in_cond_before(OPT_EQUAL, col_no,
						sel_node->search_cond,
						sel_node, nth_table, &op);
		if (col_no == mix_id_col_no) {
			ut_ad(exp == NULL);
			
			index_plan[j] = NULL;
			*last_op = '=';
			goodness += 4;
		} else if (exp) {			
			/* The value for this column is exactly known already
			at this stage of the join */

			index_plan[j] = exp;
			*last_op = op;
			goodness += 4;
		} else {
			/* Look for non-equality comparisons */

			exp = opt_look_for_col_in_cond_before(OPT_COMPARISON,
						col_no, sel_node->search_cond,
						sel_node, nth_table, &op);
			if (exp) {
				index_plan[j] = exp;
				*last_op = op;
				goodness += 2;
			}				
		
			break;
		}	
	}

	if (goodness >= 4 * dict_index_get_n_unique(index)) {
		goodness += 1024;

		if (index->type & DICT_CLUSTERED) {

			goodness += 1024;
		}
	}

	/* We have to test for goodness here, as last_op may note be set */
	if (goodness && index->type & DICT_CLUSTERED) {

		goodness++;
	}

	return(goodness);
}

/***********************************************************************
Calculates the number of matched fields based on an index goodness. */
UNIV_INLINE
ulint
opt_calc_n_fields_from_goodness(
/*============================*/
				/* out: number of excatly or partially matched
				fields */
	ulint	goodness)	/* in: goodness */
{
	return(((goodness % 1024) + 2) / 4);
}

/***********************************************************************
Converts a comparison operator to the corresponding search mode PAGE_CUR_GE,
... */
UNIV_INLINE
ulint
opt_op_to_search_mode(
/*==================*/
			/* out: search mode */
	ibool	asc,	/* in: TRUE if the rows should be fetched in an
			ascending order */
	ulint	op)	/* in: operator '=', PARS_GE_TOKEN, ... */
{
	if (op == '=') {
		if (asc) {
			return(PAGE_CUR_GE);
		} else {
			return(PAGE_CUR_LE);
		}	
	} else if (op == '<') {
		ut_a(!asc);
		return(PAGE_CUR_L);