Arena can replace MemPool in most scenarios. Except for memory reuse, MemPool supports reuse of previous memory chunks after clear, but Arena does not.
Some comparisons between MemPool and Arena:
1. Expansion
Arena is less than 128M index 2 alloc chunk; more than 128M memory, allocate 128M * n > `size`, n is equal to the minimum value that satisfies the expression;
MemPool less than 512K index 2 alloc chunk, greater than 512K memory, separately apply for a `size` length chunk
After Arena applied for a chunk larger than 128M last time, the minimum chunk applied for after that is 128M. Does this seem to be a waste of memory? MemPool is also similar. After the chunk of 512K was applied for last time, the minimum chunk of subsequent applications is 512K.
2. Alignment
MemPool defaults to 16 alignment, because memtable and other places that use int128 require 16 alignment;
Arena has no default alignment;
3. Memory reuse
Arena only supports `rollback`, which reuses the memory of the current chunk, usually the memory requested last time.
MemPool supports clear(), all chunks can be reused; or call ReturnPartialAllocation() to roll back the last requested memory; if the last chunk has no memory, search for the most free chunk for allocation
4. Realloc
Arena supports realloc contiguous memory; it also supports realloc contiguous memory from any position at the time of the last allocation. The difference between `alloc_continue` and `realloc` is:
1. Alloc_continue does not need to specify the old size, but the default old size = head->pos - range_start
2. alloc_continue supports expansion from range_start when additional_bytes is between head and pos, which is equivalent to reusing a part of memory, while realloc completely allocates a new memory
MemPool does not support realloc, but supports transferring or absorbing chunks between two MemPools
5. check mem limit
MemPool checks the mem limit, and Arena checks at the Allocator layer.
6. Support for ASAN
Arena does something extra
7. Error handling
MemPool supports returning the error message of application failure directly through `Status`, and Arena throws Exception.
Tests that Arena can consider
1. After the last applied chunk is larger than 128M, the minimum applied chunk is 128M, which seems to waste memory;
2. Support clear, memory multiplexing;
3. Increase the large list, alloc the memory larger than 128M, and the size is equal to `size`, so as to avoid the current chunk not being fully used, which is wasteful.
4. In some cases, it may be possible to allocate backwards to find chunks t
There are many type definitions in BE. Should unify the type system and simplify the development.
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Co-authored-by: yiguolei <yiguolei@gmail.com>
when show databases/tables/table status where xxx, it will change a selectStmt to select result from
information_schema, it need catalog info to scan schema table, otherwise may get many
database or table info from multi catalog.
for example
mysql> show databases where schema_name='test';
+----------+
| Database |
+----------+
| test |
| test |
+----------+
MySQL [internal.test]> show tables from test where table_name='test_dc';
+----------------+
| Tables_in_test |
+----------------+
| test_dc |
| test_dc |
+----------------+
1. Spark can set the timestamp precision by the following configuration:
spark.sql.parquet.outputTimestampType = INT96(NANOS), TIMESTAMP_MICROS, TIMESTAMP_MILLIS
DATETIME V1 only keeps the second precision, DATETIME V2 keeps the microsecond precision.
2. If using DECIMAL V2, the BE saves the value as decimal128, and keeps the precision of decimal as (precision=27, scale=9). DECIMAL V3 can maintain the right precision of decimal
1. replace all boost::shared_ptr to std::shared_ptr
2. replace all boost::scopted_ptr to std::unique_ptr
3. replace all boost::scoped_array to std::unique<T[]>
4. replace all boost:thread to std::thread
**Authorization checking logic**
There are some problems with the current password and permission checking logic. For example:
First, we create a user by:
`create user cmy@"%" identified by "12345";`
And then 'cmy' can login with password '12345' from any hosts.
Second, we create another user by:
`create user cmy@"192.168.%" identified by "abcde";`
Because "192.168.%" has a higher priority in the permission table than "%". So when "cmy" try
to login in by password "12345" from host "192.168.1.1", it should match the second permission
entry, and will be rejected because of invalid password.
But in current implementation, Doris will continue to check password on first entry, than let it pass. So we should change it.
**Permission checking logic**
After a user login, it should has a unique identity which is got from permission table. For example,
when "cmy" from host "192.168.1.1" login, it's identity should be `cmy@"192.168.%"`. And Doris
should use this identity to check other permission, not by using the user's real identity, which is
`cmy@"192.168.1.1"`.
**Black list**
Functionally speaking, Doris only support adding WHITE LIST, which is to allow user to login from
those hosts in the white list. But is some cases, we do need a BLACK LIST function.
Fortunately, by changing the logic described above, we can simulate the effect of the BLACK LIST.
For example, First we add a user by:
`create user cmy@'%' identified by '12345';`
And now user 'cmy' can login from any hosts. and if we don't want 'cmy' to login from host A, we
can add a new user by:
`create user cmy@'A' identified by 'other_passwd';`
Because "A" has a higher priority in the permission table than "%". If 'cmy' try to login from A using password '12345', it will be rejected.
1. Apache HDFS broker support HDFS HA and Hadoop kerberos authentication.
2. New Backup and Restore function. Use Fs Broker to backup your data to HDFS or restore them from HDFS.
3. Table-Level Privileges. Grant fine-grained privileges on table-level to specified user.
4. A lot of bugs fixed.
5. Performance improvement.
