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Feature Definition:-
This feature adds invisible column functionality to server.
There is 4 level of "invisibility":
1. Not invisible (NOT_INVISIBLE) — Normal columns created by the user
2. A little bit invisible (USER_DEFINED_INVISIBLE) — columns that the
user has marked invisible. They aren't shown in SELECT * and they
don't require values in INSERT table VALUE (...). Otherwise
they behave as normal columns.
3. More invisible (SYSTEM_INVISIBLE) — Can be queried explicitly,
otherwise invisible from everything. Think ROWID sytem column.
Because they're invisible from ALTER TABLE and from CREATE TABLE
they cannot be created or dropped, they're created by the system.
User cant not create a column name which is same as of
SYSTEM_INVISIBLE.
4. Very invisible (COMPLETELY_INVISIBLE) — as above, but cannot be
queried either. They can only show up in EXPLAIN EXTENDED (might
be possible for a very invisible indexed virtual column) but
otherwise they don't exist for the user.If user creates a columns
which has same name as of COMPLETELY_INVISIBLE then
COMPLETELY_INVISIBLE column is renamed again. So it is completely
invisible from user.
Invisible Index(HA_INVISIBLE_KEY):-
Creation of invisible columns require a new type of index which
will be only visible to system. User cant see/alter/create/delete
this index. If user creates a index which is same name as of
invisible index then it will be renamed.
Syntax Details:-
Only USER_DEFINED_INVISIBLE column can be created by user. This
can be created by adding INVISIBLE suffix after column definition.
Create table t1( a int invisible, b int);
Rules:-
There are some rules/restrictions related to use of invisible columns
1. All the columns in table cant be invisible.
Create table t1(a int invisible); \\error
Create table t1(a int invisible, b int invisble); \\error
2. If you want invisible column to be NOT NULL then you have to supply
Default value for the column.
Create table t1(a int, b int not null); \\error
3. If you create a view/create table with select * then this wont copy
invisible fields. So newly created view/table wont have any invisible
columns.
Create table t2 as select * from t1;//t2 wont have t1 invisible column
Create view v1 as select * from t1;//v1 wont have t1 invisible column
4. Invisibility wont be forwarded to next table in any case of create
table/view as select */(a,b,c) from table.
Create table t2 as select a,b,c from t1; // t2 will have t1 invisible
// column(b), but this wont be invisible in t2
Create view v1 as select a,b,c from t1; // v1 will have t1 invisible
// column(b), but this wont be invisible in v1
Implementation Details:-
Parsing:- INVISIBLE_SYM is added into vcol_attribute(so its like unique
suffix), It is also added into keyword_sp_not_data_type so that table
can have column with name invisible.
Implementation detail is given by each modified function/created function.
(Some function are left as they were self explanatory)
(m= Modified, n= Newly Created)
mysql_prepare_create_table(m):- Extra checks for invisible columns are
added. Also some DEBUG_EXECUTE_IF are also added for test cases.
mysql_prepare_alter_table(m):- Now this will drop all the
COMPLETELY_INVISIBLE column and HA_INVISIBLE_KEY index. Further
Modifications are made to stop drop/change/delete of SYSTEM_INVISIBLE
column.
build_frm_image(m):- Now this allows incorporating field_visibility
status into frm image. To remain compatible with old frms
field_visibility info will be only written when any of the field is
not NOT_INVISIBLE.
extra2_write_additional_field_properties(n):- This will write field
visibility info into buffer. We first write EXTRA2_FIELD_FLAGS into
buffer/frm , then each next char will have field_visibility for each
field.
init_from_binary_frm_image(m):- Now if we get EXTRA2_FIELD_FLAGS,
then we will read the next n(n= number of fields) chars and set the
field_visibility. We also increment
thd->status_var.feature_invisible_columns. One important thing to
note if we find out that key contains a field whose visibility is
> USER_DEFINED_INVISIBLE then , we declare this key as invisible
key.
sql_show.cc is changed accordingly to make show table, show keys
correct.
mysql_insert(m):- If we get to know that we are doing insert in
this way insert into t1 values(1,1); without explicitly specifying
columns, then we check for if we have invisible fields if yes then
we reset the whole record, Why ? Because first we want hidden columns
to get default/null value. Second thing auto_increment has property
no default and no null which voilates invisible key rule 2, And
because of this it was giving error. Reseting table->record[0]
eliminates this issue. More info put breakpoint on handler::write_row
and see auto_increment value.
fill_record(m):- we continue loop if we find invisible column because
this is already reseted/will get its value if it is default.
Test cases:- Since we can not directly add > USER_DEFINED_INVISIBLE
column then I have debug_dbug to create it in mysql_prepare_create_table.
Patch Credit:- Serg Golubchik
170 lines
4.2 KiB
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170 lines
4.2 KiB
Plaintext
drop table if exists t1;
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set sql_mode="";
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flush status;
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show status like "feature%";
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Variable_name Value
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Feature_check_constraint 0
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Feature_delay_key_write 0
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Feature_dynamic_columns 0
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Feature_fulltext 0
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Feature_gis 0
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Feature_invisible_columns 0
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Feature_locale 0
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Feature_subquery 0
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Feature_timezone 0
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Feature_trigger 0
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Feature_window_functions 0
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Feature_xml 0
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#
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# Feature GIS
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#
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CREATE TABLE t1 (g POINT);
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SHOW FIELDS FROM t1;
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Field Type Null Key Default Extra
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g point YES NULL
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INSERT INTO t1 VALUES
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(PointFromText('POINT(10 10)')),
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(PointFromText('POINT(20 10)')),
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(PointFromText('POINT(20 20)')),
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(PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));
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drop table t1;
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show status like "feature_gis";
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Variable_name Value
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Feature_gis 3
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#
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# Feature dynamic columns
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#
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set @a= COLUMN_CREATE(1, 1212 AS int);
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set @b= column_add(@a, 2, 1212 as integer);
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select column_get(@b, 2 as integer);
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column_get(@b, 2 as integer)
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1212
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show status like "feature_dynamic_columns";
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Variable_name Value
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Feature_dynamic_columns 2
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#
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# Feature fulltext
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#
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CREATE TABLE t1 (a VARCHAR(200), b TEXT, FULLTEXT (a,b)) engine=myisam;
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INSERT INTO t1 VALUES('MySQL has now support', 'for full-text search'),
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('Full-text indexes', 'are called collections'),
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('Only MyISAM tables','support collections'),
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('Function MATCH ... AGAINST()','is used to do a search'),
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('Full-text search in MySQL', 'implements vector space model');
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select * from t1 where MATCH(a,b) AGAINST ("collections");
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a b
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Only MyISAM tables support collections
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Full-text indexes are called collections
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select * from t1 where MATCH(a,b) AGAINST ("indexes");
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a b
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Full-text indexes are called collections
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drop table t1;
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show status like "feature_fulltext";
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Variable_name Value
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Feature_fulltext 2
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#
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# Feature locale
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#
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SET lc_messages=sr_RS;
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SET lc_messages=en_US;
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show status like "feature_locale";
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Variable_name Value
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Feature_locale 2
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#
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# Feature subquery
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#
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select (select 2);
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(select 2)
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2
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SELECT (SELECT 1) UNION SELECT (SELECT 2);
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(SELECT 1)
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1
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2
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create table t1 (a int);
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insert into t1 values (2);
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select (select a from t1 where t1.a=t2.a), a from t1 as t2;
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(select a from t1 where t1.a=t2.a) a
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2 2
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drop table t1;
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show status like "feature_subquery";
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Variable_name Value
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Feature_subquery 4
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#
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# Feature timezone
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#
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SELECT FROM_UNIXTIME(unix_timestamp()) > "1970-01-01";
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FROM_UNIXTIME(unix_timestamp()) > "1970-01-01"
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1
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set time_zone="+03:00";
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SELECT FROM_UNIXTIME(unix_timestamp()) > "1970-01-01";
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FROM_UNIXTIME(unix_timestamp()) > "1970-01-01"
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1
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set time_zone= @@global.time_zone;
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show status like "feature_timezone";
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Variable_name Value
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Feature_timezone 1
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#
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# Feature triggers
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#
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create table t1 (i int);
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# let us test some very simple trigger
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create trigger trg before insert on t1 for each row set @a:=1;
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set @a:=0;
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select @a;
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@a
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0
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insert into t1 values (1),(2);
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select @a;
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@a
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1
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SHOW TRIGGERS IN test like 't1';
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Trigger Event Table Statement Timing Created sql_mode Definer character_set_client collation_connection Database Collation
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trg INSERT t1 set @a:=1 BEFORE # root@localhost latin1 latin1_swedish_ci latin1_swedish_ci
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drop trigger trg;
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drop table t1;
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show status like "%trigger%";
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Variable_name Value
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Binlog_group_commit_trigger_count 0
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Binlog_group_commit_trigger_lock_wait 0
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Binlog_group_commit_trigger_timeout 0
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Com_create_trigger 1
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Com_drop_trigger 1
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Com_show_create_trigger 0
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Com_show_triggers 1
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Executed_triggers 2
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Feature_trigger 2
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#
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# Feature xml
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#
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SET @xml='<a aa1="aa1" aa2="aa2">a1<b ba1="ba1">b1<c>c1</c>b2</b>a2</a>';
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SELECT extractValue(@xml,'/a');
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extractValue(@xml,'/a')
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a1 a2
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select updatexml('<div><div><span>1</span><span>2</span></div></div>',
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'/','<tr><td>1</td><td>2</td></tr>') as upd1;
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upd1
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<tr><td>1</td><td>2</td></tr>
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show status like "feature_xml";
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Variable_name Value
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Feature_xml 2
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#
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# Feature delayed_keys
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#
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create table t1 (a int, key(a)) engine=myisam delay_key_write=1;
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insert into t1 values(1);
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insert into t1 values(2);
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drop table t1;
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create table t1 (a int, key(a)) engine=aria delay_key_write=1;
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insert into t1 values(1);
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insert into t1 values(2);
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drop table t1;
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show status like "feature_delay_key_write";
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Variable_name Value
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Feature_delay_key_write 2
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create table t1 (a int check (a > 5));
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create table t2 (b int, constraint foo check (b < 10));
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drop table t1, t2;
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show status like "feature_check_constraint";
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Variable_name Value
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Feature_check_constraint 2
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