btr0btr.c Add more documentation about B-tree latching (a16f3360) · Commits · Software / OSDI20 Artifacts / mariadb

innobase/btr/btr0btr.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -22,6 +22,25 @@ Created 6/2/1994 Heikki Tuuri
		#include "ibuf0ibuf.h"

		/*
		Latching strategy of the InnoDB B-tree
		--------------------------------------
		A tree latch protects all non-leaf nodes of the tree. Each node of a tree
		also has a latch of its own.

		A B-tree operation normally first acquires an S-latch on the tree. It
		searches down the tree and releases the tree latch when it has the
		leaf node latch. To save CPU time we do not acquire any latch on
		non-leaf nodes of the tree during a search, those pages are only bufferfixed.

		If an operation needs to restructure the tree, it acquires an X-latch on
		the tree before searching to a leaf node. If it needs, for example, to
		split a leaf,
		(1) InnoDB decides the split point in the leaf,
		(2) allocates a new page,
		(3) inserts the appropriate node pointer to the first non-leaf level,
		(4) releases the tree X-latch,
		(5) and then moves records from the leaf to the new allocated page.

		Node pointers
		-------------
		Leaf pages of a B-tree contain the index records stored in the

innobase/dict/dict0dict.c

+5 −16

Original line number	Diff line number	Diff line
		@@ -308,29 +308,18 @@ dict_table_autoinc_get(
		}

		/************************************************************************
		Reads the autoinc counter value, 0 if not yet initialized. Does not
		increment the counter. */
		Decrements the autoinc counter value by 1. */

		ib_longlong
		dict_table_autoinc_read(
		/====================/
		/* out: value of the counter */
		void
		dict_table_autoinc_decrement(
		/=========================/
		dict_table_t* table) /* in: table */
		{
		ib_longlong value;

		mutex_enter(&(table->autoinc_mutex));

		if (!table->autoinc_inited) {

		value = 0;
		} else {
		value = table->autoinc;
		}
		table->autoinc = table->autoinc - 1;

		mutex_exit(&(table->autoinc_mutex));

		return(value);
		}

		/************************************************************************

innobase/include/dict0dict.h

+4 −6

Original line number	Diff line number	Diff line
		@@ -114,13 +114,11 @@ dict_table_autoinc_get(
		/* out: value for a new row, or 0 */
		dict_table_t* table); /* in: table */
		/************************************************************************
		Reads the autoinc counter value, 0 if not yet initialized. Does not
		increment the counter. */
		Decrements the autoinc counter value by 1. */

		ib_longlong
		dict_table_autoinc_read(
		/====================/
		/* out: value of the counter */
		void
		dict_table_autoinc_decrement(
		/=========================/
		dict_table_t* table); /* in: table */
		/************************************************************************
		Peeks the autoinc counter value, 0 if not yet initialized. Does not

sql/ha_innodb.cc

+47 −21

Original line number	Diff line number	Diff line
		@@ -405,8 +405,6 @@ ha_innobase::update_thd(
		return(0);
		}

		/* The code here appears for documentational purposes only. Not used
		or tested yet. Will be used in 4.1. */
		/*********************************************************************
		Call this when you have opened a new table handle in HANDLER, before you
		call index_read_idx() etc. Actually, we can let the cursor stay open even
		@@ -667,14 +665,14 @@ innobase_commit_low(
		/================/
		trx_t* trx) /* in: transaction handle */
		{
		if (current_thd->slave_thread)
		{
		if (current_thd->slave_thread) {
		/* Update the replication position info inside InnoDB */
		#ifdef NEED_TO_BE_FIXED
		trx->mysql_relay_log_file_name = active_mi->rli.log_file_name;
		trx->mysql_relay_log_pos = active_mi->rli.relay_log_pos;
		#endif
		trx->mysql_master_log_file_name= active_mi->rli.master_log_name;
		trx->mysql_master_log_file_name
		= active_mi->rli.master_log_name;
		trx->mysql_master_log_pos = ((ib_longlong)
		(active_mi->rli.master_log_pos +
		active_mi->rli.event_len +
		@@ -692,7 +690,8 @@ innobase_commit(
		/* out: 0 or error number */
		THD* thd, /* in: MySQL thread handle of the user for whom
		the transaction should be committed */
		void* trx_handle)/* in: InnoDB trx handle or NULL: NULL means
		void* trx_handle)/* in: InnoDB trx handle or
		&innodb_dummy_stmt_trx_handle: the latter means
		that the current SQL statement ended, and we should
		mark the start of a new statement with a savepoint */
		{
		@@ -716,6 +715,7 @@ innobase_commit(

		if (trx_handle != (void*)&innodb_dummy_stmt_trx_handle) {
		innobase_commit_low(trx);
		thd->transaction.all.innodb_active_trans=0;
		}

		/* Release possible statement level resources */
		@@ -772,7 +772,9 @@ innobase_rollback(
		/* out: 0 or error number */
		THD* thd, /* in: handle to the MySQL thread of the user
		whose transaction should be rolled back */
		void* trx_handle)/* in: InnoDB trx handle or a dummy stmt handle */
		void* trx_handle)/* in: InnoDB trx handle or a dummy stmt handle;
		the latter means we roll back the latest SQL
		statement */
		{
		int error = 0;
		trx_t* trx;
		@@ -796,6 +798,7 @@ innobase_rollback(

		if (trx_handle != (void*)&innodb_dummy_stmt_trx_handle) {
		error = trx_rollback_for_mysql(trx);
		thd->transaction.all.innodb_active_trans=0;
		} else {
		error = trx_rollback_last_sql_stat_for_mysql(trx);
		}
		@@ -1497,6 +1500,8 @@ ha_innobase::write_row(
		int error;
		longlong auto_inc;
		longlong dummy;
		ibool incremented_auto_inc_for_stat = FALSE;
		ibool incremented_auto_inc_counter = FALSE;

		DBUG_ENTER("ha_innobase::write_row");

		@@ -1567,6 +1572,7 @@ ha_innobase::write_row(
		assign sequential values from the counter. */

		auto_inc_counter_for_this_stat++;
		incremented_auto_inc_for_stat = TRUE;

		auto_inc = auto_inc_counter_for_this_stat;

		@@ -1615,7 +1621,12 @@ ha_innobase::write_row(
		}
		}

		/* The following call gets the value of the auto-inc
		counter of the table and increments it by 1 */

		auto_inc = dict_table_autoinc_get(prebuilt->table);
		incremented_auto_inc_counter = TRUE;

		srv_conc_exit_innodb(prebuilt->trx);

		/* We can give the new value for MySQL to place in
		@@ -1652,6 +1663,20 @@ ha_innobase::write_row(

		srv_conc_exit_innodb(prebuilt->trx);

		if (error != DB_SUCCESS) {
		/* If the insert did not succeed we restore the value of
		the auto-inc counter we used; note that this behavior was
		introduced only in version 4.0.4 */

		if (incremented_auto_inc_counter) {
		dict_autoinc_decrement(prebuilt->table);
		}

		if (incremented_auto_inc_for_stat) {
		auto_inc_counter_for_this_stat--;
		}
		}

		prebuilt->trx->ignore_duplicates_in_insert = FALSE;

		error = convert_error_code_to_mysql(error, user_thd);
		@@ -3311,7 +3336,7 @@ ha_innobase::update_table_comment(
		{
		row_prebuilt_t* prebuilt = (row_prebuilt_t*)innobase_prebuilt;
		uint length = strlen(comment);
		char* str = my_malloc(length + 550, MYF(0));
		char* str = my_malloc(length + 16500, MYF(0));
		char* pos;

		/* Warning: since it is not sure that MySQL calls external_lock
		@@ -3333,10 +3358,12 @@ ha_innobase::update_table_comment(
		(pos,"InnoDB free: %lu kB",
		(ulong) innobase_get_free_space()));

		/* We assume 450 - length bytes of space to print info */
		/* We assume 16000 - length bytes of space to print info; the limit
		16000 bytes is arbitrary, and MySQL could handle at least 64000
		bytes */

		if (length < 450) {
		dict_print_info_on_foreign_keys(FALSE, pos, 450 - length,
		if (length < 16000) {
		dict_print_info_on_foreign_keys(FALSE, pos, 16000 - length,
		prebuilt->table);
		}

		@@ -3508,7 +3535,6 @@ ha_innobase::external_lock(
		& (OPTION_NOT_AUTOCOMMIT \| OPTION_BEGIN))) {

		innobase_commit(thd, trx);
		thd->transaction.all.innodb_active_trans=0;
		}
		}
		}