row0upd.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

/******************************************************
Update of a row

(c) 1996 Innobase Oy

Created 12/27/1996 Heikki Tuuri
*******************************************************/

#include "row0upd.h"

#ifdef UNIV_NONINL
#include "row0upd.ic"
#endif

#include "dict0dict.h"
#include "dict0boot.h"
#include "dict0crea.h"
#include "mach0data.h"
#include "trx0undo.h"
#include "btr0btr.h"
#include "btr0cur.h"
#include "que0que.h"
#include "row0ins.h"
#include "row0sel.h"
#include "row0row.h"
#include "rem0cmp.h"
#include "lock0lock.h"
#include "log0log.h"
#include "pars0sym.h"
#include "eval0eval.h"
#include "buf0lru.h"


/* What kind of latch and lock can we assume when the control comes to
   -------------------------------------------------------------------
an update node?
--------------
Efficiency of massive updates would require keeping an x-latch on a
clustered index page through many updates, and not setting an explicit
x-lock on clustered index records, as they anyway will get an implicit
x-lock when they are updated. A problem is that the read nodes in the
graph should know that they must keep the latch when passing the control
up to the update node, and not set any record lock on the record which
will be updated. Another problem occurs if the execution is stopped,
as the kernel switches to another query thread, or the transaction must
wait for a lock. Then we should be able to release the latch and, maybe,
acquire an explicit x-lock on the record.
	Because this seems too complicated, we conclude that the less
efficient solution of releasing all the latches when the control is
transferred to another node, and acquiring explicit x-locks, is better. */

/* How is a delete performed? If there is a delete without an
explicit cursor, i.e., a searched delete, there are at least
two different situations:
the implicit select cursor may run on (1) the clustered index or
on (2) a secondary index. The delete is performed by setting
the delete bit in the record and substituting the id of the
deleting transaction for the original trx id, and substituting a
new roll ptr for previous roll ptr. The old trx id and roll ptr
are saved in the undo log record. Thus, no physical changes occur
in the index tree structure at the time of the delete. Only
when the undo log is purged, the index records will be physically
deleted from the index trees.

The query graph executing a searched delete would consist of
a delete node which has as a subtree a select subgraph.
The select subgraph should return a (persistent) cursor
in the clustered index, placed on page which is x-latched.
The delete node should look for all secondary index records for
this clustered index entry and mark them as deleted. When is
the x-latch freed? The most efficient way for performing a
searched delete is obviously to keep the x-latch for several
steps of query graph execution. */

/***************************************************************
Checks if an update vector changes some of the first ordering fields of an
index record. This is only used in foreign key checks and we can assume
that index does not contain column prefixes. */
static
ibool
row_upd_changes_first_fields_binary(
/*================================*/
				/* out: TRUE if changes */
	dtuple_t*	entry,	/* in: old value of index entry */
	dict_index_t*	index,	/* in: index of entry */
	upd_t*		update,	/* in: update vector for the row */
	ulint		n);	/* in: how many first fields to check */


/*************************************************************************
Checks if index currently is mentioned as a referenced index in a foreign
key constraint. */
static
ibool
row_upd_index_is_referenced(
/*========================*/
				/* out: TRUE if referenced; NOTE that since
				we do not hold dict_operation_lock
				when leaving the function, it may be that
				the referencing table has been dropped when
				we leave this function: this function is only
				for heuristic use! */
	dict_index_t*	index,	/* in: index */
	trx_t*		trx)	/* in: transaction */
{
	dict_table_t*	table		= index->table;
	dict_foreign_t*	foreign;
	ibool		froze_data_dict	= FALSE;

	if (!UT_LIST_GET_FIRST(table->referenced_list)) {

		return(FALSE);
	}

	if (trx->dict_operation_lock_mode == 0) {
		row_mysql_freeze_data_dictionary(trx);
		froze_data_dict = TRUE;
	}

	foreign = UT_LIST_GET_FIRST(table->referenced_list);

	while (foreign) {
		if (foreign->referenced_index == index) {

			if (froze_data_dict) {
				row_mysql_unfreeze_data_dictionary(trx);
			}

			return(TRUE);
		}

		foreign = UT_LIST_GET_NEXT(referenced_list, foreign);
	}
	
	if (froze_data_dict) {
		row_mysql_unfreeze_data_dictionary(trx);
	}

	return(FALSE);
}

/*************************************************************************
Checks if possible foreign key constraints hold after a delete of the record
under pcur. NOTE that this function will temporarily commit mtr and lose the
pcur position! */
static
ulint
row_upd_check_references_constraints(
/*=================================*/
				/* out: DB_SUCCESS or an error code */
	upd_node_t*	node,	/* in: row update node */
	btr_pcur_t*	pcur,	/* in: cursor positioned on a record; NOTE: the
				cursor position is lost in this function! */
	dict_table_t*	table,	/* in: table in question */
	dict_index_t*	index,	/* in: index of the cursor */
	que_thr_t*	thr,	/* in: query thread */
	mtr_t*		mtr)	/* in: mtr */
{
	dict_foreign_t*	foreign;
	mem_heap_t*	heap;
	dtuple_t*	entry;
	trx_t*		trx;
	rec_t*		rec;
	ulint		err;
	ibool		got_s_lock	= FALSE;

	if (UT_LIST_GET_FIRST(table->referenced_list) == NULL) {

		return(DB_SUCCESS);
	}

	trx = thr_get_trx(thr);

	rec = btr_pcur_get_rec(pcur);

	heap = mem_heap_create(500);

	entry = row_rec_to_index_entry(ROW_COPY_DATA, index, rec, heap);

	mtr_commit(mtr);	

	mtr_start(mtr);	
	
	if (trx->dict_operation_lock_mode == 0) {
		got_s_lock = TRUE;

		row_mysql_freeze_data_dictionary(trx);
	}
		
	foreign = UT_LIST_GET_FIRST(table->referenced_list);

	while (foreign) {
		/* Note that we may have an update which updates the index
		record, but does NOT update the first fields which are
		referenced in a foreign key constraint. Then the update does
		NOT break the constraint. */

		if (foreign->referenced_index == index
		    && (node->is_delete
		       || row_upd_changes_first_fields_binary(entry, index,
			    		node->update, foreign->n_fields))) {
			    				
			if (foreign->foreign_table == NULL) {
				dict_table_get(foreign->foreign_table_name,
									trx);
			}

			if (foreign->foreign_table) {
				mutex_enter(&(dict_sys->mutex));

				(foreign->foreign_table
				->n_foreign_key_checks_running)++;

				mutex_exit(&(dict_sys->mutex));
			}

			/* NOTE that if the thread ends up waiting for a lock
			we will release dict_operation_lock temporarily!
			But the counter on the table protects 'foreign' from
			being dropped while the check is running. */
			
			err = row_ins_check_foreign_constraint(FALSE, foreign,
							table, entry, thr);

			if (foreign->foreign_table) {
				mutex_enter(&(dict_sys->mutex));

				ut_a(foreign->foreign_table
				->n_foreign_key_checks_running > 0);

				(foreign->foreign_table
				->n_foreign_key_checks_running)--;

				mutex_exit(&(dict_sys->mutex));
			}

			if (err != DB_SUCCESS) {
				if (got_s_lock) {
					row_mysql_unfreeze_data_dictionary(
									trx);
				}

				mem_heap_free(heap);

				return(err);
			}
		}

		foreign = UT_LIST_GET_NEXT(referenced_list, foreign);
	}

	if (got_s_lock) {
		row_mysql_unfreeze_data_dictionary(trx);
	}

	mem_heap_free(heap);
	
	return(DB_SUCCESS);
}

/*************************************************************************
Creates an update node for a query graph. */

upd_node_t*
upd_node_create(
/*============*/
				/* out, own: update node */
	mem_heap_t*	heap)	/* in: mem heap where created */
{
	upd_node_t*	node;

	node = mem_heap_alloc(heap, sizeof(upd_node_t));
	node->common.type = QUE_NODE_UPDATE;

	node->state = UPD_NODE_UPDATE_CLUSTERED;
	node->select_will_do_update = FALSE;
	node->in_mysql_interface = FALSE;

	node->row = NULL;
	node->ext_vec = NULL;
	node->index = NULL;
	node->update = NULL;
	
	node->foreign = NULL;
	node->cascade_heap = NULL;
	node->cascade_node = NULL;
	
	node->select = NULL;
	
	node->heap = mem_heap_create(128);
	node->magic_n = UPD_NODE_MAGIC_N;	

	node->cmpl_info = 0;
	
	return(node);
}

/*************************************************************************
Updates the trx id and roll ptr field in a clustered index record in database
recovery. */

void
row_upd_rec_sys_fields_in_recovery(
/*===============================*/
	rec_t*		rec,	/* in: record */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint		pos,	/* in: TRX_ID position in rec */
	dulint		trx_id,	/* in: transaction id */
	dulint		roll_ptr)/* in: roll ptr of the undo log record */
{
	byte*	field;
	ulint	len;

	field = rec_get_nth_field(rec, offsets, pos, &len);
	ut_ad(len == DATA_TRX_ID_LEN);
	trx_write_trx_id(field, trx_id);

	field = rec_get_nth_field(rec, offsets, pos + 1, &len);
	ut_ad(len == DATA_ROLL_PTR_LEN);
	trx_write_roll_ptr(field, roll_ptr);
}

/*************************************************************************
Sets the trx id or roll ptr field of a clustered index entry. */

void
row_upd_index_entry_sys_field(
/*==========================*/
	dtuple_t*	entry,	/* in: index entry, where the memory buffers
				for sys fields are already allocated:
				the function just copies the new values to
				them */
	dict_index_t*	index,	/* in: clustered index */
	ulint		type,	/* in: DATA_TRX_ID or DATA_ROLL_PTR */
	dulint		val)	/* in: value to write */
{
	dfield_t*	dfield;
	byte*		field;
	ulint		pos;

	ut_ad(index->type & DICT_CLUSTERED);

	pos = dict_index_get_sys_col_pos(index, type);

	dfield = dtuple_get_nth_field(entry, pos);
	field = dfield_get_data(dfield);

	if (type == DATA_TRX_ID) {
		trx_write_trx_id(field, val);
	} else {
		ut_ad(type == DATA_ROLL_PTR);
		trx_write_roll_ptr(field, val);
	}
}

/***************************************************************
Returns TRUE if row update changes size of some field in index or if some
field to be updated is stored externally in rec or update. */

ibool
row_upd_changes_field_size_or_external(
/*===================================*/
				/* out: TRUE if the update changes the size of
				some field in index or the field is external
				in rec or update */
	dict_index_t*	index,	/* in: index */
	const ulint*	offsets,/* in: rec_get_offsets(rec, index) */
	upd_t*		update)	/* in: update vector */
{
	upd_field_t*	upd_field;
	dfield_t*	new_val;
	ulint		old_len;
	ulint		new_len;
	ulint		n_fields;
	ulint		i;

	ut_ad(rec_offs_validate(NULL, index, offsets));
	n_fields = upd_get_n_fields(update);

	for (i = 0; i < n_fields; i++) {
		upd_field = upd_get_nth_field(update, i);

		new_val = &(upd_field->new_val);
		new_len = new_val->len;

		if (new_len == UNIV_SQL_NULL && !rec_offs_comp(offsets)) {
			/* A bug fixed on Dec 31st, 2004: we looked at the
			SQL NULL size from the wrong field! We may backport
			this fix also to 4.0. The merge to 5.0 will be made
			manually immediately after we commit this to 4.1. */

			new_len = dtype_get_sql_null_size(
					dict_index_get_nth_type(index,
						upd_field->field_no));
		}

		old_len = rec_offs_nth_size(offsets, upd_field->field_no);

		if (rec_offs_comp(offsets)
		    && rec_offs_nth_sql_null(offsets, upd_field->field_no)) {
			/* Note that in the compact table format, for a
			variable length field, an SQL NULL will use zero
			bytes in the offset array at the start of the physical
			record, but a zero-length value (empty string) will
			use one byte! Thus, we cannot use update-in-place
			if we update an SQL NULL varchar to an empty string! */

			old_len = UNIV_SQL_NULL;
		}

		if (old_len != new_len) {

			return(TRUE);
		}
		
		if (rec_offs_nth_extern(offsets, upd_field->field_no)) {

			return(TRUE);
		}

		if (upd_field->extern_storage) {

			return(TRUE);
		}
	}

	return(FALSE);
}

/***************************************************************
Replaces the new column values stored in the update vector to the record
given. No field size changes are allowed. This function is used only for
a clustered index */

void
row_upd_rec_in_place(
/*=================*/
	rec_t*		rec,	/* in/out: record where replaced */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	upd_t*		update)	/* in: update vector */
{
	upd_field_t*	upd_field;
	dfield_t*	new_val;
	ulint		n_fields;
	ulint		i;

	ut_ad(rec_offs_validate(rec, NULL, offsets));

	rec_set_info_bits(rec, rec_offs_comp(offsets), update->info_bits);

	n_fields = upd_get_n_fields(update);

	for (i = 0; i < n_fields; i++) {
		upd_field = upd_get_nth_field(update, i);
		new_val = &(upd_field->new_val);
		
		rec_set_nth_field(rec, offsets, upd_field->field_no,
						dfield_get_data(new_val),
						dfield_get_len(new_val));
	}
}

/*************************************************************************
Writes into the redo log the values of trx id and roll ptr and enough info
to determine their positions within a clustered index record. */

byte*
row_upd_write_sys_vals_to_log(
/*==========================*/
				/* out: new pointer to mlog */
	dict_index_t*	index,	/* in: clustered index */
	trx_t*		trx,	/* in: transaction */
	dulint		roll_ptr,/* in: roll ptr of the undo log record */
	byte*		log_ptr,/* pointer to a buffer of size > 20 opened
				in mlog */
	mtr_t*		mtr __attribute__((unused))) /* in: mtr */
{
	ut_ad(index->type & DICT_CLUSTERED);
	ut_ad(mtr);

	log_ptr += mach_write_compressed(log_ptr,
			dict_index_get_sys_col_pos(index, DATA_TRX_ID));

	trx_write_roll_ptr(log_ptr, roll_ptr);
	log_ptr += DATA_ROLL_PTR_LEN;	

	log_ptr += mach_dulint_write_compressed(log_ptr, trx->id);

	return(log_ptr);
}

/*************************************************************************
Parses the log data of system field values. */

byte*
row_upd_parse_sys_vals(
/*===================*/
			/* out: log data end or NULL */
	byte*	ptr,	/* in: buffer */
	byte*	end_ptr,/* in: buffer end */
	ulint*	pos,	/* out: TRX_ID position in record */
	dulint*	trx_id,	/* out: trx id */
	dulint*	roll_ptr)/* out: roll ptr */
{
	ptr = mach_parse_compressed(ptr, end_ptr, pos);

	if (ptr == NULL) {

		return(NULL);
	}

	if (end_ptr < ptr + DATA_ROLL_PTR_LEN) {