adding config to control Varchar behavior

datafusion/common/src/config.rs

@@ -204,6 +204,11 @@ config_namespace! {
         /// MySQL, PostgreSQL, Hive, SQLite, Snowflake, Redshift, MsSQL, ClickHouse, BigQuery, and Ansi.
         pub dialect: String, default = "generic".to_string()
 
+        /// If true, permit lengths for `VARCHAR` such as `VARCHAR(20)`, but
+        /// ignore the length. If false, error if a `VARCHAR` with a length is
+        /// specified. The Arrow type system does not have a notion of maximum
+        /// string length and thus DataFusion can not enforce such limits.
+        pub support_varchar_with_length: bool, default = true
     }
 }
 
@@ -303,6 +308,7 @@ config_namespace! {
         /// statistics into the same file groups.
         /// Currently experimental
         pub split_file_groups_by_statistics: bool, default = false
+
     }
 }
 

datafusion/core/src/execution/session_state.rs

@@ -615,6 +615,7 @@ impl SessionState {
         ParserOptions {
             parse_float_as_decimal: sql_parser_options.parse_float_as_decimal,
             enable_ident_normalization: sql_parser_options.enable_ident_normalization,
+            support_varchar_with_length: sql_parser_options.support_varchar_with_length,
         }
     }
 

datafusion/sql/src/planner.rs

@@ -103,13 +103,15 @@ pub trait ContextProvider {
 pub struct ParserOptions {
     pub parse_float_as_decimal: bool,
     pub enable_ident_normalization: bool,
+    pub support_varchar_with_length: bool,
 }
 
 impl Default for ParserOptions {
     fn default() -> Self {
         Self {
             parse_float_as_decimal: false,
             enable_ident_normalization: true,
+            support_varchar_with_length: true,
         }
     }
 }
@@ -404,12 +406,17 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
             SQLDataType::UnsignedInt(_) | SQLDataType::UnsignedInteger(_) | SQLDataType::UnsignedInt4(_) => {
                 Ok(DataType::UInt32)
             }
+            SQLDataType::Varchar(length) => {
+                match (length, self.options.support_varchar_with_length) {
+                    (Some(_), false) => plan_err!("does not support Varchar with length, please set `support_varchar_with_length` to be true"),
+                    _ => Ok(DataType::Utf8),
+                }
+            }
             SQLDataType::UnsignedBigInt(_) | SQLDataType::UnsignedInt8(_) => Ok(DataType::UInt64),
             SQLDataType::Float(_) => Ok(DataType::Float32),
             SQLDataType::Real | SQLDataType::Float4 => Ok(DataType::Float32),
             SQLDataType::Double | SQLDataType::DoublePrecision | SQLDataType::Float8 => Ok(DataType::Float64),
             SQLDataType::Char(_)
-            | SQLDataType::Varchar(_)
             | SQLDataType::Text
             | SQLDataType::String(_) => Ok(DataType::Utf8),
             SQLDataType::Timestamp(None, tz_info) => {

datafusion/sql/tests/sql_integration.rs

@@ -84,6 +84,7 @@ fn parse_decimals() {
             ParserOptions {
                 parse_float_as_decimal: true,
                 enable_ident_normalization: false,
+                support_varchar_with_length: false,
             },
         );
     }
@@ -137,6 +138,7 @@ fn parse_ident_normalization() {
             ParserOptions {
                 parse_float_as_decimal: false,
                 enable_ident_normalization,
+                support_varchar_with_length: false,
             },
         );
         if plan.is_ok() {

datafusion/sqllogictest/test_files/information_schema.slt

@@ -237,6 +237,7 @@ datafusion.optimizer.top_down_join_key_reordering true
 datafusion.sql_parser.dialect generic
 datafusion.sql_parser.enable_ident_normalization true
 datafusion.sql_parser.parse_float_as_decimal false
+datafusion.sql_parser.support_varchar_with_length true
 
 # show all variables with verbose
 query TTT rowsort
@@ -318,6 +319,7 @@ datafusion.optimizer.top_down_join_key_reordering true When set to true, the phy
 datafusion.sql_parser.dialect generic Configure the SQL dialect used by DataFusion's parser; supported values include: Generic, MySQL, PostgreSQL, Hive, SQLite, Snowflake, Redshift, MsSQL, ClickHouse, BigQuery, and Ansi.
 datafusion.sql_parser.enable_ident_normalization true When set to true, SQL parser will normalize ident (convert ident to lowercase when not quoted)
 datafusion.sql_parser.parse_float_as_decimal false When set to true, SQL parser will parse float as decimal type
+datafusion.sql_parser.support_varchar_with_length true If true, permit lengths for `VARCHAR` such as `VARCHAR(20)`, but ignore the length. If false, error if a `VARCHAR` with a length is specified. The Arrow type system does not have a notion of maximum string length and thus DataFusion can not enforce such limits.
 
 # show_variable_in_config_options
 query TT

datafusion/sqllogictest/test_files/strings.slt

@@ -78,3 +78,52 @@ e1
 p2
 p2e1
 p2m1e1
+
+## VARCHAR with length support
+
+# Lengths can be used by default
+query T
+SELECT '12345'::VARCHAR(2);
+----
+12345
+
+# Lengths can not be used when the config setting is disabled
+
+statement ok
+set datafusion.sql_parser.support_varchar_with_length = false;
+
+query error
+SELECT '12345'::VARCHAR(2);
+
+query error
+SELECT s::VARCHAR(2) FROM (VALUES ('12345')) t(s);
+
+statement ok
+create table vals(s char) as values('abc'), ('def');
+
+query error
+SELECT s::VARCHAR(2) FROM vals
+
+# Lengths can be used when the config setting is enabled
+
+statement ok
+set datafusion.sql_parser.support_varchar_with_length = true;
+
+query T
+SELECT '12345'::VARCHAR(2)
+----
+12345
+
+query T
+SELECT s::VARCHAR(2) FROM (VALUES ('12345')) t(s)
+----
+12345
+
+query T
+SELECT s::VARCHAR(2) FROM vals
+----
+abc
+def
+
+statement ok
+drop table vals;

docs/source/user-guide/configs.md

@@ -113,3 +113,4 @@ Environment variables are read during `SessionConfig` initialisation so they mus
 | datafusion.sql_parser.parse_float_as_decimal                            | false                     | When set to true, SQL parser will parse float as decimal type                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
 | datafusion.sql_parser.enable_ident_normalization                        | true                      | When set to true, SQL parser will normalize ident (convert ident to lowercase when not quoted)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
 | datafusion.sql_parser.dialect                                           | generic                   | Configure the SQL dialect used by DataFusion's parser; supported values include: Generic, MySQL, PostgreSQL, Hive, SQLite, Snowflake, Redshift, MsSQL, ClickHouse, BigQuery, and Ansi.                                                                                                                                                                                                                                                                                                                                                                                                                  |
+| datafusion.sql_parser.support_varchar_with_length                       | true                      | If true, permit lengths for `VARCHAR` such as `VARCHAR(20)`, but ignore the length. If false, error if a `VARCHAR` with a length is specified. The Arrow type system does not have a notion of maximum string length and thus DataFusion can not enforce such limits.                                                                                                                                                                                                                                                                                                                                   |