F.34. mchar — additional data types for compatibility with Microsoft SQL Server #
The mchar module provides additional data types for compatibility with Microsoft SQL Server (MS SQL).
F.34.1. Overview #
This module has been designed to improve 1C Enterprise support, most popular Russian CRM and ERP system.
It implements types MCHAR and MVARCHAR, which are bug-to-bug compatible with MS SQL CHAR and VARCHAR respectively. Additionally, these types use the ICU library for comparison and case conversion, so their behavior is identical across different operating systems.
Postgres Pro also includes citext extension which provides types similar to MCHAR. But this extension doesn't emulate MS-SQL behavior concerning end-of-value whitespace.
Differences from Postgres Pro standard CHAR and VARCHAR are:
Case insensitive comparison
Handling of the whitespace at the end of string
These types are always stored as two-byte unicode value regardless of database encoding.
F.34.2. Additional types #
mchar— analog of the MS SQL char typemvarchar— analog of the MS SQL varchar type
F.34.3. MCHAR and MVARCHAR features #
Defines
length(str)functionDefines
substr(str, pos[, length])functionDefines
||operator, which would be applied to concatenate any (mchar and mvarchar) argumentsDefines set of operators:
<,<=,=,>=,>for case-insensitive comparison (ICU)Defines set of operators:
&<,&<=,&=,&>=,&>to case-sensitive comparison (ICU)Implicit cast between
mcharandmvarchartypesB-tree and Hash-index support
The
LIKE [ESCAPE]operator supportThe
SIMILAR TO [ESCAPE]operator supportThe ~ operator (POSIX regexp) support
Index support for the LIKE operator
F.34.4. Authors #
Oleg Bartunov <oleg@sai.msu.ru>
Teodor Sigaev <teodor@sigaev.ru>