Details
-
Task
-
Status: Open (View Workflow)
-
Major
-
Resolution: Unresolved
-
None
-
None
Description
MDEV-30164 introduced a class Simple_tokenizer. It supports loose parsing of a list of name=value pairs:
,,name1=value1, name2 = value2 ,,, name3=value3,,
|
- Any number of spaces are allowed at any place between tokens
- Empty name=value pairs are allowed, i.e. multiple commas can go in a row. This makes it convenient to "edit" the value of @@character_set_collations, for example, pass it to REGEX_REPLACE() and cut a fragment using a simpler regular expression.
SET @@character_set_collations='big5=big5_bin,latin1=latin1_bin,utf8mb4=utf8mb4_bin'; |
SELECT REGEXP_REPLACE(@@character_set_collations,'big5=[a-z0-9_]*',''); |
+-----------------------------------------------------------------+
|
| REGEXP_REPLACE(@@character_set_collations,'big5=[a-z0-9_]*','') |
|
+-----------------------------------------------------------------+
|
| ,latin1=latin1_bin,utf8mb4=utf8mb4_bin |
|
+-----------------------------------------------------------------+
|
Notice, REGEXP_REPLACE() made an empty pair in the beginning of the result, however SET still understands the result:
SET @@character_set_collations=REGEXP_REPLACE(@@character_set_collations,'big5=[a-z0-9_]*',''); |
SELECT @@character_set_collations; |
+---------------------------------------+
|
| @@character_set_collations |
|
+---------------------------------------+
|
| latin1=latin1_bin,utf8mb4=utf8mb4_bin |
|
+---------------------------------------+
|
Simple_tokenizer is charset-unaware. It expects only ASCII data. It can be reused for some other system variables where we parse pure ASCII data with complex format, such as lists:
- sql_mode
- optimizer_switch
- log_slow_filter
- myisam_recover_options
- slave_transaction_retry_errors
For now every variable implement its own tokenizers, so behaviour can vary:
-- Only-spaces are not allowed
|
SET optimizer_switch=' '; |
ERROR 1231 (42000): Variable 'optimizer_switch' can't be set to the value of ' ' |
-- Empty pairs are not allowed
|
SET optimizer_switch=','; |
ERROR 1231 (42000): Variable 'optimizer_switch' can't be set to the value of ',' |
-- Spaces before commas are allowed
|
SET optimizer_switch='index_merge=on ,index_merge_union=on'; |
Query OK, 0 rows affected (0.000 sec) |
-- However spaces after commas are not allowed
|
SET optimizer_switch='index_merge=on, index_merge_union=on'; |
ERROR 1231 (42000): Variable 'optimizer_switch' can't be set to the value of ' index_merge_union=on' |
Let's reuse the class Simple_tokenizer to:
- make all variables work in the same style
- reduce duplicate/similar code
Attachments
Issue Links
- relates to
-
-
- Closed
-