Safe Haskell	None
Language	Haskell2010

Hmssql.Query.Lexer

Description

Finding the positional parameter references (@p1, @p2, ...) in T-SQL text, so that mkQuery can turn them into placeholders that renumber when queries are concatenated.

This is not a T-SQL parser. It only knows enough of the lexical structure to leave alone what is inside string literals (... and N..., with '' for a quote), quoted identifiers ("..." with "", and [...] with ]]) and comments (-- ... to the end of the line, and /* ... */, which T-SQL nests). Everything unterminated runs to the end of the text; the scanner never fails.

Synopsis

data Fragment
- = Static !Text
- | Placeholder !Int
lexPlaceholders :: Text -> [Fragment]
isVariableChar :: Char -> Bool

Documentation

data Fragment Source #

A piece of SQL text, or a reference to a positional parameter (1-based).

Constructors

Static !Text
Placeholder !Int

Instances

Instances details

Show Fragment Source #
Instance details Defined in Hmssql.Query.Lexer Methods showsPrec :: Int -> Fragment -> ShowS # show :: Fragment -> String # showList :: [Fragment] -> ShowS #
Eq Fragment Source #
Instance details Defined in Hmssql.Query.Lexer Methods (==) :: Fragment -> Fragment -> Bool # (/=) :: Fragment -> Fragment -> Bool #

lexPlaceholders :: Text -> [Fragment] Source #

Split T-SQL text into static text and positional placeholders.

A placeholder is @p (either case) followed by one or more ASCII digits, standing alone as a name: the character before the @ is not @ or a character of a variable name (so @@p1 and x@p1 are text), and the character after the digits is not one either (so @p1x, @p1_old and @p1é are other variables). @P01 is placeholder 1. More than nine digits is text (no request has that many parameters).

Adjacent static text is merged; the result concatenates back to the input with each placeholder rendered as @pN.

The scanner only finds the placeholders; the static text between two of them is one slice of the input. (Building it from the pieces the scanner passes over, appending as it went, was quadratic in the number of special characters between placeholders: every - of a - b, every '' in a string, every / or * in a comment.)

isVariableChar :: Char -> Bool Source #

A character of a T-SQL variable name after the leading @: a letter, combining mark, decimal digit or letter number from the Basic Multilingual Plane, or one of @, #, $ and _. (SQL Server rejects surrogates in identifiers, so nothing above U+FFFF.)