iffyio commented on code in PR #1735:
URL:
https://github.com/apache/datafusion-sqlparser-rs/pull/1735#discussion_r1974849855
##########
src/dialect/mod.rs:
##########
@@ -201,6 +201,33 @@ pub trait Dialect: Debug + Any {
false
}
+ /// Determine whether the dialect strips the backslash when escaping LIKE
wildcards (%, _).
+ ///
+ /// [MySQL] has a special case when escaping single quoted strings which
leaves these unescaped
+ /// so they can be used in LIKE patterns without double-escaping (as is
necessary in other
+ /// escaping dialects, such as [Snowflake]). Generally, special characters
have escaping rules
+ /// causing them to be replaced with a different byte sequences (e.g.
`'\0'` becoming the zero
+ /// byte), and the default if an escaped character does not have a
specific escaping rule is to
+ /// strip the backslash (e.g. there is no rule for `h`, so `'\h' = 'h'`).
MySQL's special case
+ /// for ignoring LIKE wildcard escapes is to *not* strip the backslash, so
that `'\%' = '\\%'`.
+ /// This applies to all string literals though, not just those used in
LIKE patterns.
+ ///
+ /// ```text
+ /// mysql> select '\_', hex('\\'), hex('_'), hex('\_');
+ /// +----+-----------+----------+-----------+
+ /// | \_ | hex('\\') | hex('_') | hex('\_') |
+ /// +----+-----------+----------+-----------+
+ /// | \_ | 5C | 5F | 5C5F |
+ /// +----+-----------+----------+-----------+
+ /// 1 row in set (0.00 sec)
+ /// ```
+ ///
+ /// [MySQL]: https://dev.mysql.com/doc/refman/8.4/en/string-literals.html
+ /// [Snowflake]:
https://docs.snowflake.com/en/sql-reference/functions/like#usage-notes
+ fn ignores_like_wildcard_escapes(&self) -> bool {
Review Comment:
```suggestion
fn ignores_wildcard_escapes(&self) -> bool {
```
maybe we drop the `like` part? as the comment suggests if its nothing
special about the `LIKE` syntax and more of a general string literal escape
behavior
##########
src/tokenizer.rs:
##########
@@ -807,6 +807,9 @@ pub struct Tokenizer<'a> {
/// If true (the default), the tokenizer will un-escape literal
/// SQL strings See [`Tokenizer::with_unescape`] for more details.
unescape: bool,
+ /// If true, the tokenizer will not escape % and _, for use in in LIKE
patterns. See
+ /// [`Dialect::ignores_like_wildcard_escapes`] for more details.
+ ignore_like_wildcard_escapes: bool,
Review Comment:
was it a reason to store this value here vs relying solely on the dialect
via `self.dialect.ignores_like_wildcard_escapes()` when needed?
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