From aa1950c226f00a90092aea23cdbee247240775b9 Mon Sep 17 00:00:00 2001
From: Alexander Beedie <alexander-beedie@users.noreply.github.com>
Date: Tue, 30 Jul 2024 13:35:27 +0400
Subject: [PATCH] feat: Add `SQL` interface support for PostgreSQL
 dollar-quoted string literals (#17940)

---
 crates/polars-sql/src/sql_expr.rs         | 28 ++++++++++++-----------
 py-polars/tests/unit/sql/test_literals.py | 18 ++++++++++++++-
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/crates/polars-sql/src/sql_expr.rs b/crates/polars-sql/src/sql_expr.rs
index ffcb3dbc4998..9374a5fd3229 100644
--- a/crates/polars-sql/src/sql_expr.rs
+++ b/crates/polars-sql/src/sql_expr.rs
@@ -907,9 +907,10 @@ impl SQLExprVisitor<'_> {
     ///
     /// See [SQLValue] and [LiteralValue] for more details
     fn visit_literal(&self, value: &SQLValue) -> PolarsResult<Expr> {
+        // note: double-quoted strings will be parsed as identifiers, not literals
         Ok(match value {
             SQLValue::Boolean(b) => lit(*b),
-            SQLValue::DoubleQuotedString(s) => lit(s.clone()),
+            SQLValue::DollarQuotedString(s) => lit(s.value.clone()),
             #[cfg(feature = "binary_encoding")]
             SQLValue::HexStringLiteral(x) => {
                 if x.len() % 2 != 0 {
@@ -929,12 +930,14 @@ impl SQLExprVisitor<'_> {
             },
             SQLValue::SingleQuotedByteStringLiteral(b) => {
                 // note: for PostgreSQL this represents a BIT string literal (eg: b'10101') not a BYTE string
-                // literal (see https://www.postgresql.org/docs/current/datatype-bit.html), but sqlparser
+                // literal (see https://www.postgresql.org/docs/current/datatype-bit.html), but sqlparser-rs
                 // patterned the token name after BigQuery (where b'str' really IS a byte string)
                 bitstring_to_bytes_literal(b)?
             },
             SQLValue::SingleQuotedString(s) => lit(s.clone()),
-            other => polars_bail!(SQLInterface: "value {:?} is not supported", other),
+            other => {
+                polars_bail!(SQLInterface: "value {:?} is not a supported literal type", other)
+            },
         })
     }
 
@@ -946,6 +949,14 @@ impl SQLExprVisitor<'_> {
     ) -> PolarsResult<AnyValue> {
         Ok(match value {
             SQLValue::Boolean(b) => AnyValue::Boolean(*b),
+            SQLValue::DollarQuotedString(s) => AnyValue::StringOwned(s.clone().value.into()),
+            #[cfg(feature = "binary_encoding")]
+            SQLValue::HexStringLiteral(x) => {
+                if x.len() % 2 != 0 {
+                    polars_bail!(SQLSyntax: "hex string literal must have an even number of digits; found '{}'", x)
+                };
+                AnyValue::BinaryOwned(hex::decode(x.clone()).unwrap())
+            },
             SQLValue::Null => AnyValue::Null,
             SQLValue::Number(s, _) => {
                 let negate = match op {
@@ -968,13 +979,6 @@ impl SQLExprVisitor<'_> {
                 }
                 .map_err(|_| polars_err!(SQLInterface: "cannot parse literal: {:?}", s))?
             },
-            #[cfg(feature = "binary_encoding")]
-            SQLValue::HexStringLiteral(x) => {
-                if x.len() % 2 != 0 {
-                    polars_bail!(SQLSyntax: "hex string literal must have an even number of digits; found '{}'", x)
-                };
-                AnyValue::BinaryOwned(hex::decode(x.clone()).unwrap())
-            },
             SQLValue::SingleQuotedByteStringLiteral(b) => {
                 // note: for PostgreSQL this represents a BIT literal (eg: b'10101') not BYTE
                 let bytes_literal = bitstring_to_bytes_literal(b)?;
@@ -985,9 +989,7 @@ impl SQLExprVisitor<'_> {
                     },
                 }
             },
-            SQLValue::SingleQuotedString(s) | SQLValue::DoubleQuotedString(s) => {
-                AnyValue::StringOwned(s.into())
-            },
+            SQLValue::SingleQuotedString(s) => AnyValue::StringOwned(s.into()),
             other => polars_bail!(SQLInterface: "value {:?} is not currently supported", other),
         })
     }
diff --git a/py-polars/tests/unit/sql/test_literals.py b/py-polars/tests/unit/sql/test_literals.py
index 4bed3f432565..805169039476 100644
--- a/py-polars/tests/unit/sql/test_literals.py
+++ b/py-polars/tests/unit/sql/test_literals.py
@@ -72,7 +72,7 @@ def test_bit_hex_errors() -> None:
 
         with pytest.raises(
             SQLInterfaceError,
-            match=r'NationalStringLiteral\("hmmm"\) is not supported',
+            match=r'NationalStringLiteral\("hmmm"\) is not a supported literal',
         ):
             pl.sql_expr("N'hmmm'")
 
@@ -93,6 +93,22 @@ def test_bit_hex_membership() -> None:
         assert dff["y"].to_list() == [1, 4]
 
 
+def test_dollar_quoted_literals() -> None:
+    df = pl.sql(
+        """
+        SELECT
+          $$xyz$$ AS dq1,
+          $q$xyz$q$ AS dq2,
+          $tag$xyz$tag$ AS dq3,
+          $QUOTE$xyz$QUOTE$ AS dq4,
+        """
+    ).collect()
+    assert df.to_dict(as_series=False) == {f"dq{n}": ["xyz"] for n in range(1, 5)}
+
+    df = pl.sql("SELECT $$x$z$$ AS dq").collect()
+    assert df.item() == "x$z"
+
+
 def test_intervals() -> None:
     with pl.SQLContext(df=None, eager=True) as ctx:
         out = ctx.execute(