This patch implements an Oracle style function to_number()
with the following signatures:
- to_number(number_or_string_subject)
- to_number(string_subject, string_format)
The function is implemented in sql/item_numconvfunc.cc.
The function returns the DOUBLE data type for
all signatures and input data types.
The format parser understands the following components:
- Digits: 0, 9
- Hex digits: X
- Group separators: comma (,) and G
- Decimal delimiers: period (.) and D
- Approximate number signature: EEEE
- Currency/numeric flags: $ and B
- Currency signatures: C, L, U
- Sign signatures: S, MI, PR
- Special format signatures: V, TM, TM9, TME
- Format flag: FM
Note, the parser was implemented assuming that we'll also have the
oppostite function to_char() soon for numeric input.
So it parser all known components.
However, the function to_number() does not support:
- Formats V, TM, TM9, TME. to_number() returns NULL if the format
string has these components.
These componens are supported only by to_char() in Oracle.
Features not inclided into this patch:
- The ON CONVERSION ERROR clause
- The third parameter (nlsparam)
- Internationalized components: G, D, C, L, U.
These features will be implemented later, under terms of MDEV-36978.
Notable changes in the other files:
- item_func.h: adding Item_handled_func::Handler_double
- simple_parser.h: adding a number of *CONTAINER* templates
They help to save on duplicate code when creating classes
suitable for passing into parsing templates such as OPT, OR2C, OR3C, etc
- simple_parser.h: Adding parsing templates OR4C and OR5C
- simple_parser.h: Moving the template "OPT" towars the beginning of the file
Rule parsing templates TOKEN, TokenChoice, AND2, OR2C, OR3C, OR4C, OR5C, LIST
now provide a sub-class Opt, to parse its optional rule.
- simple_parser.h: Adding "explicit" to all "operator bool" definitions
- Renaming Parser_templates::TOKEN to Parser_templates::TokenParser
- Adding "explicit" to all "operator bool()" templates/classes,
to avoid hidden implicit conversion (to int, void*, etc).
- Renaming the LIST template parameter ELEMENT to ELEMENT_PARSER,
to make it clearer what it is for.
- Renaming the OPT template parameter RULE to RULE_PARSER,
to make it clearer what it is for.
This patch adds a way to override default collations
(or "character set collations") for desired character sets.
The SQL standard says:
> Each collation known in an SQL-environment is applicable to one
> or more character sets, and for each character set, one or more
> collations are applicable to it, one of which is associated with
> it as its character set collation.
In MariaDB, character set collations has been hard-coded so far,
e.g. utf8mb4_general_ci has been a hard-coded character set collation
for utf8mb4.
This patch allows to override (globally per server, or per session)
character set collations, so for example, uca1400_ai_ci can be set as a
character set collation for Unicode character sets
(instead of compiled xxx_general_ci).
The array of overridden character set collations is stored in a new
(session and global) system variable @@character_set_collations and
can be set as a comma separated list of charset=collation pairs, e.g.:
SET @@character_set_collations='utf8mb3=uca1400_ai_ci,utf8mb4=uca1400_ai_ci';
The variable is empty by default, which mean use the hard-coded
character set collations (e.g. utf8mb4_general_ci for utf8mb4).
The variable can also be set globally by passing to the server startup command
line, and/or in my.cnf.
