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351a8eecf0
Changing the way how a the following conditions are evaluated:
WHERE timestamp_column=datetime_const_expr
(for all comparison operators: =, <=>, <, >, <=, >=, <> and for NULLIF)
Before the change it was always performed as DATETIME.
That was not efficient, as involved per-row TIMESTAMP->DATETIME conversion
for timestamp_column. For example, in case of the SYSTEM time zone
it involved a localtime_r() call, which is known to be slow.
After the change it's performed as TIMESTAMP in many cases.
This allows to avoid per-row conversion, as it works the other way around:
datetime_const_expr is converted to TIMESTAMP once before the execution stage.
Note, datetime_const_expr must be inside monotone continuous periods of
the current time zone, i.e. not near these anomalies:
- DST changes (spring forward, fall back)
- leap seconds
295 lines
8.3 KiB
Text
295 lines
8.3 KiB
Text
create table emp
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(
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emp_id int,
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name varchar(127),
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mgr int
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) with system versioning;
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insert into emp values (1, 'bill', 0),
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(2, 'bill', 1),
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(3, 'kate', 1);
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set @ts=now(6);
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delete from emp;
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insert into emp values (4, 'john', 1);
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with ancestors as (select * from emp) select * from ancestors;
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emp_id name mgr
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4 john 1
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set @tmp= "with ancestors as (select * from emp) select * from ancestors";
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prepare stmt from @tmp;
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execute stmt;
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emp_id name mgr
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4 john 1
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drop prepare stmt;
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with ancestors as (select * from emp for system_time all) select * from ancestors;
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emp_id name mgr
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1 bill 0
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2 bill 1
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3 kate 1
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4 john 1
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set @tmp= "with ancestors as (select * from emp for system_time all) select * from ancestors";
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prepare stmt from @tmp;
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execute stmt;
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emp_id name mgr
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1 bill 0
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2 bill 1
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3 kate 1
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4 john 1
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drop prepare stmt;
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with recursive ancestors as (select * from emp) select * from ancestors;
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emp_id name mgr
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4 john 1
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set @tmp= "with recursive ancestors as (select * from emp) select * from ancestors";
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prepare stmt from @tmp;
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execute stmt;
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emp_id name mgr
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4 john 1
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drop prepare stmt;
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select emp_id from (select emp_id from emp where row_end>'2031-1-1') as tmp;
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emp_id
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4
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set @tmp= "select emp_id from (select emp_id from emp where row_end>'2031-1-1') as tmp";
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prepare stmt from @tmp;
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execute stmt;
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emp_id
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4
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drop prepare stmt;
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with recursive
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ancestors
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as
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(
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select e.emp_id, e.name, e.mgr
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from emp as e
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where name = 'john'
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union
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select ee.emp_id, ee.name, ee.mgr
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from emp as ee, ancestors as a
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where ee.mgr = a.emp_id
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)
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select * from ancestors;
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emp_id name mgr
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4 john 1
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set @tmp= "
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with recursive
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ancestors
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as
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(
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select e.emp_id, e.name, e.mgr
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from emp as e
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where name = 'john'
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union
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select ee.emp_id, ee.name, ee.mgr
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from emp as ee, ancestors as a
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where ee.mgr = a.emp_id
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)
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select * from ancestors";
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prepare stmt from @tmp;
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execute stmt;
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emp_id name mgr
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4 john 1
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drop prepare stmt;
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with recursive
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ancestors
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as
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(
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select e.emp_id, e.name, e.mgr
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from emp for system_time as of timestamp @ts as e
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where name = 'bill'
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union
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select ee.emp_id, ee.name, ee.mgr
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from emp for system_time as of timestamp @ts as ee,
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ancestors as a
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where ee.mgr = a.emp_id
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)
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select * from ancestors;
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emp_id name mgr
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1 bill 0
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2 bill 1
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3 kate 1
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set @tmp= "
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with recursive
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ancestors
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as
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(
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select e.emp_id, e.name, e.mgr
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from emp for system_time as of timestamp @ts as e
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where name = 'bill'
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union
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select ee.emp_id, ee.name, ee.mgr
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from emp for system_time as of timestamp @ts as ee,
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ancestors as a
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where ee.mgr = a.emp_id
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)
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select * from ancestors";
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prepare stmt from @tmp;
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execute stmt;
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emp_id name mgr
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1 bill 0
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2 bill 1
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3 kate 1
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drop prepare stmt;
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drop table emp;
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create or replace table t1 (x int) with system versioning;
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create or replace table t2 (y int) with system versioning;
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insert into t1 values (1);
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set @t0= now(6);
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delete from t1;
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insert into t1 values (2);
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insert into t2 values (10);
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select * from (select *, t1.row_end, t1.row_end as endo from t1) as s0;
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x row_end endo
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2 # #
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select * from (select *, t1.row_end, t2.row_start from t1, t2) as s0;
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x y row_end row_start
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2 10 # #
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# SYSTEM_TIME propagation from inner to outer
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select * from (select * from t1 for system_time as of timestamp @t0, t2) as s0;
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x y
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1 10
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with s1 as (select * from t1 for system_time as of timestamp @t0, t2) select * from s1;
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x y
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1 10
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# leading table selection
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select * from (select *, t1.row_end from t2, t1 for system_time as of timestamp @t0) as s2;
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y x row_end
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10 1 #
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with s3 as (select *, t1.row_end from t2, t1 for system_time as of timestamp @t0) select * from s3;
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y x row_end
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10 1 #
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### VIEW instead of t1
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set @q= concat("create view vt1 as select * from t1 for system_time as of timestamp '", @t0, "'");
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prepare q from @q;
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execute q;
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drop prepare q;
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create view vt2 as select * from t1;
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# SYSTEM_TIME propagation from view
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select * from vt1;
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x
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1
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# SYSTEM_TIME propagation from inner to outer
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select * from (select * from vt1, t2) as s0;
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x y
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1 10
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### SYSTEM_TIME clash
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select * from (select * from t1 for system_time all) for system_time all as dt0;
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ERROR HY000: Table `dt0` is not system-versioned
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select * from vt1 for system_time all;
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ERROR HY000: Table `vt1` is not system-versioned
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with dt1 as (select * from t1 for system_time all)
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select * from dt1 for system_time all;
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ERROR HY000: Table `dt1` is not system-versioned
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### UNION
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set @t1= now(6);
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delete from t2;
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insert into t2 values (3);
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# SYSTEM_TIME is not propagated
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select x from t1 union
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select y from t2;
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x
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2
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3
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select x from t1 for system_time as of @t0 union
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select y from t2;
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x
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1
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3
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select x from t1 union
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select y from t2 for system_time as of @t1;
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x
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2
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10
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select x from t1 for system_time as of @t0 union
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select y from t2 for system_time as of @t1;
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x
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1
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10
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# LEFT/RIGHT JOIN
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create or replace table t1 (x int, y int) with system versioning;
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create or replace table t2 (x int, y int) with system versioning;
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insert into t1 values (1, 1), (1, 2), (1, 3), (4, 4), (5, 5);
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insert into t2 values (1, 2), (2, 1), (3, 1);
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## Outer or inner SYSTEM_TIME produces same expression
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 100.00 Using where
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1 SIMPLE t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using join buffer (flat, BNL join)
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Query A:
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Note 1003 select `test`.`t1`.`x` AS `x`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP current_timestamp(6) join `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP current_timestamp(6) where `test`.`t1`.`x` = `test`.`t2`.`x` and `test`.`t2`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t2`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu'
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 100.00 Using where
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1 SIMPLE t1 ALL NULL NULL NULL NULL 5 100.00 Using where; Using join buffer (flat, BNL join)
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Query B:
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Note 1003 select `test`.`t1`.`x` AS `x`,`test`.`t1`.`y` AS `y1`,`test`.`t2`.`x` AS `x2`,`test`.`t2`.`y` AS `y2` from `test`.`t1` FOR SYSTEM_TIME AS OF TIMESTAMP current_timestamp(6) join `test`.`t2` FOR SYSTEM_TIME AS OF TIMESTAMP current_timestamp(6) where `test`.`t1`.`x` = `test`.`t2`.`x` and `test`.`t2`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t2`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_end` > TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu' and `test`.`t1`.`row_start` <= TIMESTAMP/*WITH LOCAL TIME ZONE*/'YYYY-MM-DD hh:ss:mm:.uuuuuu'
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Fine result: queries A and B are equal.
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## LEFT JOIN: t1, t2 versioned
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select * from (
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select t1.x as LJ1_x1, t1.y as y1, t2.x as x2, t2.y as y2
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from t1 left join t2 on t1.x = t2.x)
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as derived;
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LJ1_x1 y1 x2 y2
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1 1 1 2
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1 2 1 2
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1 3 1 2
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4 4 NULL NULL
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5 5 NULL NULL
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alter table t2 drop system versioning;
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## LEFT JOIN: t1 versioned
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select * from (
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select t1.x as LJ2_x1, t1.y as y1, t2.x as x2, t2.y as y2
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from t1 left join t2 on t1.x = t2.x)
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as derived;
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LJ2_x1 y1 x2 y2
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1 1 1 2
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1 2 1 2
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1 3 1 2
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4 4 NULL NULL
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5 5 NULL NULL
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alter table t1 drop system versioning;
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alter table t2 add system versioning;
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## LEFT JOIN: t2 versioned
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select * from (
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select t1.x as LJ3_x1, t1.y as y1, t2.x as x2, t2.y as y2
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from t1 left join t2 on t1.x = t2.x)
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as derived;
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LJ3_x1 y1 x2 y2
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1 1 1 2
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1 2 1 2
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1 3 1 2
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4 4 NULL NULL
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5 5 NULL NULL
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alter table t1 add system versioning;
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## RIGHT JOIN: t1, t2 versioned
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select * from (
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select t1.x as RJ1_x1, t1.y as y1, t2.x as x2, t2.y as y2
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from t1 right join t2 on t1.x = t2.x)
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as derived;
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RJ1_x1 y1 x2 y2
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1 1 1 2
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1 2 1 2
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1 3 1 2
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NULL NULL 2 1
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NULL NULL 3 1
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alter table t2 drop system versioning;
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## RIGHT JOIN: t1 versioned
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select * from (
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select t1.x as RJ2_x1, t1.y as y1, t2.x as x2, t2.y as y2
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from t1 right join t2 on t1.x = t2.x)
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as derived;
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RJ2_x1 y1 x2 y2
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1 1 1 2
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1 2 1 2
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1 3 1 2
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NULL NULL 2 1
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NULL NULL 3 1
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alter table t1 drop system versioning;
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alter table t2 add system versioning;
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## RIGHT JOIN: t2 versioned
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select * from (
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select t1.x as RJ3_x1, t1.y as y1, t2.x as x2, t2.y as y2
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from t1 right join t2 on t1.x = t2.x)
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as derived;
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RJ3_x1 y1 x2 y2
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1 1 1 2
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1 2 1 2
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1 3 1 2
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NULL NULL 2 1
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NULL NULL 3 1
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drop table t1, t2;
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drop view vt1, vt2;
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