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// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.
use std::mem;
use std::str::FromStr;
use derivative::Derivative;
use mz_lowertest::MzReflect;
use mz_ore::fmt::FormatBuffer;
use mz_proto::{ProtoType, RustType, TryFromProtoError};
use mz_repr::adt::regex::Regex;
use proptest::prelude::{Arbitrary, Strategy};
use serde::{Deserialize, Serialize};
use crate::scalar::EvalError;
include!(concat!(env!("OUT_DIR"), "/mz_expr.scalar.like_pattern.rs"));
/// The number of subpatterns after which using regexes would be more efficient.
const MAX_SUBPATTERNS: usize = 5;
/// The escape character to use by default in LIKE patterns.
const DEFAULT_ESCAPE: char = '\\';
const DOUBLED_ESCAPE: &str = "\\\\";
/// Specifies escape behavior for the LIKE pattern.
#[derive(Clone, Copy, Debug)]
pub enum EscapeBehavior {
/// No escape character.
Disabled,
/// Use a custom escape character.
Char(char),
}
impl Default for EscapeBehavior {
fn default() -> EscapeBehavior {
EscapeBehavior::Char(DEFAULT_ESCAPE)
}
}
impl FromStr for EscapeBehavior {
type Err = EvalError;
fn from_str(s: &str) -> Result<EscapeBehavior, EvalError> {
let mut chars = s.chars();
match chars.next() {
None => Ok(EscapeBehavior::Disabled),
Some(c) => match chars.next() {
None => Ok(EscapeBehavior::Char(c)),
Some(_) => Err(EvalError::LikeEscapeTooLong),
},
}
}
}
/// Converts a pattern string that uses a custom escape character to one that uses the default.
pub fn normalize_pattern(pattern: &str, escape: EscapeBehavior) -> Result<String, EvalError> {
match escape {
EscapeBehavior::Disabled => Ok(pattern.replace(DEFAULT_ESCAPE, DOUBLED_ESCAPE)),
EscapeBehavior::Char(DEFAULT_ESCAPE) => Ok(pattern.into()),
EscapeBehavior::Char(custom_escape_char) => {
let mut p = String::with_capacity(2 * pattern.len());
let mut cs = pattern.chars();
while let Some(c) = cs.next() {
if c == custom_escape_char {
match cs.next() {
Some(c2) => {
p.push(DEFAULT_ESCAPE);
p.push(c2);
}
None => return Err(EvalError::UnterminatedLikeEscapeSequence),
}
} else if c == DEFAULT_ESCAPE {
p.push_str(DOUBLED_ESCAPE);
} else {
p.push(c);
}
}
p.shrink_to_fit();
Ok(p)
}
}
}
// This implementation supports a couple of different methods of matching
// text against a SQL LIKE or ILIKE pattern.
//
// The most general approach is to convert the LIKE pattern into a
// regular expression and use the well-tested Regex library to perform the
// match. This works well with complex patterns and case-insensitive matches
// that are hard to get right.
//
// That said, regular expressions aren't that efficient. For most patterns
// we can do better using built-in string matching.
pub use matcher::Matcher;
use matcher::MatcherImpl;
// This lint interacts poorly with `derivative` here; we are confident it generates
// compatible `PartialOrd` and `Ord` impls. Unfortunately it also requires we introduce
// this module to allow it.
#[allow(clippy::non_canonical_partial_ord_impl)]
mod matcher {
use super::*;
/// An object that can test whether a string matches a LIKE or ILIKE pattern.
#[derive(Debug, Clone, Deserialize, Serialize, Derivative, MzReflect)]
#[derivative(Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct Matcher {
pub pattern: String,
pub case_insensitive: bool,
#[derivative(
PartialEq = "ignore",
Hash = "ignore",
Ord = "ignore",
PartialOrd = "ignore"
)]
pub(super) matcher_impl: MatcherImpl,
}
impl Matcher {
pub fn is_match(&self, text: &str) -> bool {
match &self.matcher_impl {
MatcherImpl::String(subpatterns) => is_match_subpatterns(subpatterns, text),
MatcherImpl::Regex(r) => r.is_match(text),
}
}
}
impl RustType<ProtoMatcher> for Matcher {
fn into_proto(&self) -> ProtoMatcher {
ProtoMatcher {
pattern: self.pattern.clone(),
case_insensitive: self.case_insensitive,
}
}
fn from_proto(proto: ProtoMatcher) -> Result<Self, TryFromProtoError> {
compile(proto.pattern.as_str(), proto.case_insensitive).map_err(|eval_err| {
TryFromProtoError::LikePatternDeserializationError(eval_err.to_string())
})
}
}
#[derive(Debug, Clone, Deserialize, Serialize, MzReflect)]
pub(super) enum MatcherImpl {
String(Vec<Subpattern>),
Regex(Regex),
}
}
/// Builds a Matcher that matches a SQL LIKE pattern.
pub fn compile(pattern: &str, case_insensitive: bool) -> Result<Matcher, EvalError> {
// We would like to have a consistent, documented limit to the size of
// supported LIKE patterns. The real limiting factor is the number of states
// that can be handled by the Regex library. In testing, I was able to
// create an adversarial pattern "%a%b%c%d%e..." that started failing around
// 9 KiB, so we chose 8 KiB as the limit. This is consistent with limits
// set by other databases, like SQL Server.
// On the other hand, PostgreSQL does not have a documented limit.
if pattern.len() > 8 << 10 {
return Err(EvalError::LikePatternTooLong);
}
let subpatterns = build_subpatterns(pattern)?;
let matcher_impl = match case_insensitive || subpatterns.len() > MAX_SUBPATTERNS {
false => MatcherImpl::String(subpatterns),
true => MatcherImpl::Regex(build_regex(&subpatterns, case_insensitive)?),
};
Ok(Matcher {
pattern: pattern.into(),
case_insensitive,
matcher_impl,
})
}
pub fn any_matcher() -> impl Strategy<Value = Matcher> {
// Generates a string out of a pool of characters. The pool has at least one
// representative from the following classes of the characters (listed in
// order of its appearance in the regex):
// * Alphanumeric characters, both upper and lower-case.
// * Control characters.
// * Punctuation minus the escape character.
// * Space characters.
// * Multi-byte characters.
// * _ and %, which are special characters for a like pattern.
// * Escaped _ and %, plus the escape character itself. This implementation
// will have to be modified if we support choosing a different escape character.
//
// Syntax reference for LIKE here:
// https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
(
r"([[:alnum:]]|[[:cntrl:]]|([[[:punct:]]&&[^\\]])|[[:space:]]|华|_|%|(\\_)|(\\%)|(\\\\)){0, 50}",
bool::arbitrary(),
)
.prop_map(|(pattern, case_insensitive)| compile(&pattern, case_insensitive).unwrap())
}
// The algorithm below is based on the observation that any LIKE pattern can be
// decomposed into multiple parts:
// <PATTERN> := <SUB-PATTERN> (<SUB-PATTERN> ...)
// <SUB-PATTERN> := <WILDCARDS> <SUFFIX>
//
// The sub-patterns start with zero or more wildcard characters, eventually
// followed by (non-wildcard) literal characters. The last sub-pattern may
// have an empty SUFFIX.
//
// Example: the PATTERN "n__dl%" can be broken into the following parts:
// 1. SUB-PATTERN = <WILDCARDS ""> <SUFFIX "n">
// 2. SUB-PATTERN = <WILDCARDS "__"> <SUFFIX "dl">
// 3. SUB-PATTERN = <WILDCARDS "%"> <SUFFIX "">
//
// The WILDCARDS can be any combination of '_', which matches exactly 1 char,
// and '%' which matches zero or more chars. These wildcards can be simplified
// down to the (min, max) of characters they might consume:
// "" = (0, 0) // doesn't consume any characters
// "_" = (1, 1) // consumes exactly one
// "%" = (0, many) // zero or more
// These are additive, so:
// "_%" = (1, many)
// "__%__" = (4, many)
// "%%%_" = (1, many)
#[derive(Debug, Default, Clone, Deserialize, Serialize, MzReflect)]
struct Subpattern {
/// The minimum number of characters that can be consumed by the wildcard expression.
consume: usize,
/// Whether the wildcard expression can consume an arbitrary number of characters.
many: bool,
/// A string literal that is expected after the wildcards.
suffix: String,
}
impl Subpattern {
/// Converts a Subpattern to an equivalent regular expression and writes it to a given string.
fn write_regex_to(&self, r: &mut String) {
match self.consume {
0 => {
if self.many {
r.push_str(".*");
}
}
1 => {
r.push('.');
if self.many {
r.push('+');
}
}
n => {
r.push_str(".{");
write!(r, "{}", n);
if self.many {
r.push(',');
}
r.push('}');
}
}
regex_syntax::escape_into(&self.suffix, r);
}
}
impl RustType<ProtoSubpattern> for Subpattern {
fn into_proto(&self) -> ProtoSubpattern {
ProtoSubpattern {
consume: self.consume.into_proto(),
many: self.many,
suffix: self.suffix.clone(),
}
}
fn from_proto(proto: ProtoSubpattern) -> Result<Self, TryFromProtoError> {
Ok(Subpattern {
consume: proto.consume.into_rust()?,
many: proto.many,
suffix: proto.suffix,
})
}
}
fn is_match_subpatterns(subpatterns: &[Subpattern], mut text: &str) -> bool {
let (subpattern, subpatterns) = match subpatterns {
[] => return text.is_empty(),
[subpattern, subpatterns @ ..] => (subpattern, subpatterns),
};
// Go ahead and skip the minimum number of characters the sub-pattern consumes:
if subpattern.consume > 0 {
let mut chars = text.chars();
if chars.nth(subpattern.consume - 1).is_none() {
return false;
}
text = chars.as_str();
}
if subpattern.many {
// The sub-pattern might consume any number of characters, but we need to find
// where it terminates so we can match any subsequent sub-patterns. We do this
// by searching for the suffix string using str::find.
//
// We could investigate using a fancier substring search like Boyer-Moore:
// https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_string-search_algorithm
//
// .. but it's likely not worth it. It's slower for small strings,
// and doesn't really start outperforming the naive approach until
// haystack sizes of 1KB or greater. See benchmarking results from:
// https://github.com/killerswan/boyer-moore-search/blob/master/README.md
//
// Another approach that may be interesting to look at is a
// hardware-optimized search:
// http://0x80.pl/articles/simd-strfind.html
if subpattern.suffix.len() == 0 {
// Nothing to find... This should only happen in the last sub-pattern.
assert!(
subpatterns.is_empty(),
"empty suffix in middle of a pattern"
);
return true;
}
// Use rfind so we perform a greedy capture, like Regex.
let mut found = text.rfind(&subpattern.suffix);
loop {
match found {
None => return false,
Some(offset) => {
let mut end = offset + subpattern.suffix.len();
if is_match_subpatterns(subpatterns, &text[end..]) {
return true;
}
// Didn't match, look for the next rfind.
if offset == 0 {
return false;
}
// Find the previous valid char byte.
loop {
end -= 1;
if text.is_char_boundary(end) {
break;
}
}
found = text[..end].rfind(&subpattern.suffix);
}
}
}
}
// No string search needed, we just use a prefix match on rest.
if !text.starts_with(&subpattern.suffix) {
return false;
}
is_match_subpatterns(subpatterns, &text[subpattern.suffix.len()..])
}
/// Breaks a LIKE pattern into a chain of sub-patterns.
fn build_subpatterns(pattern: &str) -> Result<Vec<Subpattern>, EvalError> {
let mut subpatterns = Vec::with_capacity(MAX_SUBPATTERNS);
let mut current = Subpattern::default();
let mut in_wildcard = true;
let mut in_escape = false;
for c in pattern.chars() {
match c {
c if !in_escape && c == DEFAULT_ESCAPE => {
in_escape = true;
in_wildcard = false;
}
'_' if !in_escape => {
if !in_wildcard {
current.suffix.shrink_to_fit();
subpatterns.push(mem::take(&mut current));
in_wildcard = true;
}
current.consume += 1;
}
'%' if !in_escape => {
if !in_wildcard {
current.suffix.shrink_to_fit();
subpatterns.push(mem::take(&mut current));
in_wildcard = true;
}
current.many = true;
}
c => {
current.suffix.push(c);
in_escape = false;
in_wildcard = false;
}
}
}
if in_escape {
return Err(EvalError::UnterminatedLikeEscapeSequence);
}
current.suffix.shrink_to_fit();
subpatterns.push(current);
subpatterns.shrink_to_fit();
Ok(subpatterns)
}
/// Builds a regular expression that matches some parsed Subpatterns.
fn build_regex(subpatterns: &[Subpattern], case_insensitive: bool) -> Result<Regex, EvalError> {
let mut r = String::from("^");
for sp in subpatterns {
sp.write_regex_to(&mut r);
}
r.push('$');
match Regex::new(&r, case_insensitive) {
Ok(regex) => Ok(regex),
Err(regex::Error::CompiledTooBig(_)) => Err(EvalError::LikePatternTooLong),
Err(e) => Err(EvalError::Internal(
format!("build_regex produced invalid regex: {}", e).into(),
)),
}
}
// Unit Tests
//
// Most of the unit tests for LIKE and ILIKE can be found in:
// test/sqllogictest/cockroach/like.slt
// These tests are here as a convenient place to run quick tests while
// actively working on changes to the implementation. Make sure you
// run the full test suite before submitting any changes.
#[cfg(test)]
mod test {
use super::*;
#[mz_ore::test]
fn test_normalize_pattern() {
struct TestCase<'a> {
pattern: &'a str,
escape: EscapeBehavior,
expected: &'a str,
}
let test_cases = vec![
TestCase {
pattern: "",
escape: EscapeBehavior::Disabled,
expected: "",
},
TestCase {
pattern: "ban%na!",
escape: EscapeBehavior::default(),
expected: "ban%na!",
},
TestCase {
pattern: "ban%%%na!",
escape: EscapeBehavior::Char('%'),
expected: "ban\\%\\na!",
},
TestCase {
pattern: "ban%na\\!",
escape: EscapeBehavior::Char('n'),
expected: "ba\\%\\a\\\\!",
},
TestCase {
pattern: "ban%na\\!",
escape: EscapeBehavior::Disabled,
expected: "ban%na\\\\!",
},
TestCase {
pattern: "ban\\na!",
escape: EscapeBehavior::Char('n'),
expected: "ba\\\\\\a!",
},
TestCase {
pattern: "ban\\\\na!",
escape: EscapeBehavior::Char('n'),
expected: "ba\\\\\\\\\\a!",
},
TestCase {
pattern: "food",
escape: EscapeBehavior::Char('o'),
expected: "f\\od",
},
TestCase {
pattern: "漢漢",
escape: EscapeBehavior::Char('漢'),
expected: "\\漢",
},
];
for input in test_cases {
let actual = normalize_pattern(input.pattern, input.escape).unwrap();
assert!(
actual == input.expected,
"normalize_pattern({:?}, {:?}):\n\tactual: {:?}\n\texpected: {:?}\n",
input.pattern,
input.escape,
actual,
input.expected,
);
}
}
#[mz_ore::test]
fn test_escape_too_long() {
match EscapeBehavior::from_str("foo") {
Err(EvalError::LikeEscapeTooLong) => {}
_ => {
panic!("expected error when using escape string with >1 character");
}
}
}
#[mz_ore::test]
fn test_like() {
struct Input<'a> {
haystack: &'a str,
matches: bool,
}
let input = |haystack, matches| Input { haystack, matches };
struct Pattern<'a> {
needle: &'a str,
case_insensitive: bool,
inputs: Vec<Input<'a>>,
}
let test_cases = vec![
Pattern {
needle: "ban%na!",
case_insensitive: false,
inputs: vec![input("banana!", true)],
},
Pattern {
needle: "foo",
case_insensitive: true,
inputs: vec![
input("", false),
input("f", false),
input("fo", false),
input("foo", true),
input("FOO", true),
input("Foo", true),
input("fOO", true),
input("food", false),
],
},
];
for tc in test_cases {
let matcher = compile(tc.needle, tc.case_insensitive).unwrap();
for input in tc.inputs {
let actual = matcher.is_match(input.haystack);
assert!(
actual == input.matches,
"{:?} {} {:?}:\n\tactual: {:?}\n\texpected: {:?}\n",
input.haystack,
match tc.case_insensitive {
true => "ILIKE",
false => "LIKE",
},
tc.needle,
actual,
input.matches,
);
}
}
}
}