ClickHouse: map PostgreSQL regex-match operators (~, ~*, !~, !~*) to match()

crates/polyglot-sql/src/generator.rs

@@ -20171,6 +20171,14 @@ impl Generator {
             self.generate_expression(&f.this)?;
             self.write(" ~ ");
             self.generate_expression(&f.pattern)?;
+        } else if matches!(self.config.dialect, Some(DialectType::ClickHouse)) && f.flags.is_none()
+        {
+            // ClickHouse has no REGEXP_LIKE; the regex-match operator is match(haystack, pattern).
+            self.write("match(");
+            self.generate_expression(&f.this)?;
+            self.write(", ");
+            self.generate_expression(&f.pattern)?;
+            self.write(")");
         } else if matches!(self.config.dialect, Some(DialectType::Exasol)) && f.flags.is_none() {
             // Exasol uses REGEXP_LIKE as infix binary operator
             self.generate_expression(&f.this)?;
@@ -34936,6 +34944,26 @@ impl Generator {
             self.generate_expression(&e.this)?;
             self.write(" ~* ");
             self.generate_expression(&e.expression)?;
+        } else if matches!(self.config.dialect, Some(DialectType::ClickHouse)) && e.flag.is_none() {
+            // ClickHouse has no case-insensitive regex operator; use match() with an inline
+            // (?i) flag. Inline it into a string-literal pattern for readable output, and fall
+            // back to concat() so the flag also applies to a non-literal pattern expression.
+            self.write("match(");
+            self.generate_expression(&e.this)?;
+            self.write(", ");
+            if let Expression::Literal(lit) = e.expression.as_ref() {
+                if let Literal::String(s) = lit.as_ref() {
+                    let insensitive =
+                        Expression::Literal(Box::new(Literal::String(format!("(?i){s}"))));
+                    self.generate_expression(&insensitive)?;
+                    self.write(")");
+                    return Ok(());
+                }
+            }
+            self.write("concat('(?i)', ");
+            self.generate_expression(&e.expression)?;
+            self.write("))");
+            return Ok(());
         } else if matches!(self.config.dialect, Some(DialectType::Snowflake)) {
             // Snowflake uses REGEXP_LIKE(x, pattern, 'i')
             self.write_keyword("REGEXP_LIKE");

crates/polyglot-sql/tests/postgres_regexp_clickhouse.rs

@@ -0,0 +1,70 @@
+//! Regression tests: PostgreSQL regex-match operators transpiled to ClickHouse.
+//!
+//! ClickHouse has no `REGEXP_LIKE` function and no case-insensitive regex operator; the
+//! regex-match primitive is `match(haystack, pattern)`. Previously the PostgreSQL operators
+//! `~`, `~*`, `!~`, `!~*` were emitted as `REGEXP_LIKE(...)` / an invalid `x REGEXP_ILIKE y`
+//! infix form, both of which ClickHouse rejects. They now map to `match`, with case-insensitive
+//! matching expressed via an inline `(?i)` flag.
+
+use polyglot_sql::{transpile, DialectType};
+
+fn pg_ch(sql: &str) -> String {
+    transpile(sql, DialectType::PostgreSQL, DialectType::ClickHouse)
+        .expect("PostgreSQL -> ClickHouse transpilation should succeed")
+        .join("; ")
+}
+
+#[test]
+fn regex_match_operator_maps_to_match() {
+    let cases = [
+        ("SELECT x ~ 'ab.*' FROM t", "SELECT match(x, 'ab.*') FROM t"),
+        (
+            "SELECT * FROM t WHERE name ~ '^A'",
+            "SELECT * FROM t WHERE match(name, '^A')",
+        ),
+    ];
+    for (input, expected) in cases {
+        assert_eq!(pg_ch(input), expected, "input: {input}");
+    }
+}
+
+#[test]
+fn case_insensitive_regex_operator_uses_inline_flag() {
+    // A string-literal pattern gets the (?i) flag inlined for readable output.
+    assert_eq!(
+        pg_ch("SELECT x ~* 'ab.*' FROM t"),
+        "SELECT match(x, '(?i)ab.*') FROM t"
+    );
+    // A non-literal pattern falls back to concat() so the flag still applies.
+    assert_eq!(
+        pg_ch("SELECT x ~* y FROM t"),
+        "SELECT match(x, concat('(?i)', y)) FROM t"
+    );
+}
+
+#[test]
+fn negated_regex_operators_map_to_not_match() {
+    assert_eq!(
+        pg_ch("SELECT x !~ 'ab.*' FROM t"),
+        "SELECT NOT (match(x, 'ab.*')) FROM t"
+    );
+    assert_eq!(
+        pg_ch("SELECT x !~* 'ab.*' FROM t"),
+        "SELECT NOT (match(x, '(?i)ab.*')) FROM t"
+    );
+}
+
+#[test]
+fn mysql_rlike_also_maps_to_clickhouse_match() {
+    // The mapping is on the RegexpLike node, so RLIKE/REGEXP sources benefit too.
+    assert_eq!(
+        transpile(
+            "SELECT x RLIKE 'a' FROM t",
+            DialectType::MySQL,
+            DialectType::ClickHouse
+        )
+        .expect("MySQL -> ClickHouse transpilation should succeed")
+        .join("; "),
+        "SELECT match(x, 'a') FROM t"
+    );
+}