MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
The INNODB_FT_INDEX_CACHE
table
provides token information about newly inserted rows in a
FULLTEXT
index. To avoid expensive index
reorganization during DML operations, the information about newly
indexed words is stored separately, and combined with the main
search index only when OPTIMIZE
TABLE
is run, when the server is shut down, or when the
cache size exceeds a limit defined by the
innodb_ft_cache_size
or
innodb_ft_total_cache_size
system
variable.
This table is empty initially. Before querying it, set the value
of the innodb_ft_aux_table
system
variable to the name (including the database name) of the table
that contains the FULLTEXT
index (for example,
test/articles
).
For related usage information and examples, see Section 15.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.
The INNODB_FT_INDEX_CACHE
table has
these columns:
WORD
A word extracted from the text of a newly inserted row.
FIRST_DOC_ID
The first document ID in which this word appears in the
FULLTEXT
index.
LAST_DOC_ID
The last document ID in which this word appears in the
FULLTEXT
index.
DOC_COUNT
The number of rows in which this word appears in the
FULLTEXT
index. The same word can occur
several times within the cache table, once for each
combination of DOC_ID
and
POSITION
values.
DOC_ID
The document ID of the newly inserted row. This value might
reflect the value of an ID column that you defined for the
underlying table, or it can be a sequence value generated by
InnoDB
when the table contains no suitable
column.
POSITION
The position of this particular instance of the word within
the relevant document identified by the
DOC_ID
value. The value does not represent
an absolute position; it is an offset added to the
POSITION
of the previous instance of that
word.
This table is empty initially. Before querying it, set the
value of the
innodb_ft_aux_table
system
variable to the name (including the database name) of the
table that contains the FULLTEXT
index (for
example test/articles
). The following
example demonstrates how to use the
innodb_ft_aux_table
system
variable to show information about a
FULLTEXT
index for a specified table.
mysql>USE test;
mysql>CREATE TABLE articles (
id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
title VARCHAR(200),
body TEXT,
FULLTEXT (title,body)
) ENGINE=InnoDB;
mysql>INSERT INTO articles (title,body) VALUES
('MySQL Tutorial','DBMS stands for DataBase ...'),
('How To Use MySQL Well','After you went through a ...'),
('Optimizing MySQL','In this tutorial we show ...'),
('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'),
('MySQL vs. YourSQL','In the following database comparison ...'),
('MySQL Security','When configured properly, MySQL ...');
mysql>SET GLOBAL innodb_ft_aux_table = 'test/articles';
mysql>SELECT WORD, DOC_COUNT, DOC_ID, POSITION
FROM INFORMATION_SCHEMA.INNODB_FT_INDEX_CACHE LIMIT 5;
+------------+-----------+--------+----------+ | WORD | DOC_COUNT | DOC_ID | POSITION | +------------+-----------+--------+----------+ | 1001 | 1 | 4 | 0 | | after | 1 | 2 | 22 | | comparison | 1 | 5 | 44 | | configured | 1 | 6 | 20 | | database | 2 | 1 | 31 | +------------+-----------+--------+----------+
You must have the PROCESS
privilege to query this table.
Use the INFORMATION_SCHEMA
COLUMNS
table or the
SHOW COLUMNS
statement to view
additional information about the columns of this table,
including data types and default values.
For more information about InnoDB
FULLTEXT
search, see
Section 15.6.2.4, “InnoDB FULLTEXT Indexes”, and
Section 12.10, “Full-Text Search Functions”.