ARROW-11655: [Rust][DataFusion] Postgres String Functions: left, lpad, right, rpad

rust/datafusion/README.md

@@ -64,8 +64,12 @@ DataFusion includes a simple command-line interactive SQL utility. See the [CLI
   - [x] concat
   - [x] concat_ws
   - [x] length
+  - [x] left
+  - [x] lpad
   - [x] ltrim
   - [x] octet_length
+  - [x] right
+  - [x] rpad
   - [x] rtrim
   - [x] substr
   - [x] trim

rust/datafusion/src/logical_plan/expr.rs

@@ -1069,10 +1069,14 @@ unary_scalar_expr!(CharacterLength, character_length);
 unary_scalar_expr!(CharacterLength, length);
 unary_scalar_expr!(Concat, concat);
 unary_scalar_expr!(ConcatWithSeparator, concat_ws);
+unary_scalar_expr!(Left, left);
 unary_scalar_expr!(Lower, lower);
+unary_scalar_expr!(Lpad, lpad);
 unary_scalar_expr!(Ltrim, ltrim);
 unary_scalar_expr!(MD5, md5);
 unary_scalar_expr!(OctetLength, octet_length);
+unary_scalar_expr!(Right, right);
+unary_scalar_expr!(Rpad, rpad);
 unary_scalar_expr!(Rtrim, rtrim);
 unary_scalar_expr!(SHA224, sha224);
 unary_scalar_expr!(SHA256, sha256);

rust/datafusion/src/logical_plan/mod.rs

@@ -36,9 +36,10 @@ pub use expr::{
     abs, acos, and, array, asin, atan, avg, binary_expr, bit_length, btrim, case, ceil,
     character_length, col, combine_filters, concat, concat_ws, cos, count,
     count_distinct, create_udaf, create_udf, exp, exprlist_to_fields, floor, in_list,
-    length, lit, ln, log10, log2, lower, ltrim, max, md5, min, octet_length, or, round,
-    rtrim, sha224, sha256, sha384, sha512, signum, sin, sqrt, substr, sum, tan, trim,
-    trunc, upper, when, Expr, ExprRewriter, ExpressionVisitor, Literal, Recursion,
+    left, length, lit, ln, log10, log2, lower, lpad, ltrim, max, md5, min, octet_length,
+    or, right, round, rpad, rtrim, sha224, sha256, sha384, sha512, signum, sin, sqrt,
+    substr, sum, tan, trim, trunc, upper, when, Expr, ExprRewriter, ExpressionVisitor,
+    Literal, Recursion,
 };
 pub use extension::UserDefinedLogicalNode;
 pub use operators::Operator;