[SPARK-27931][SQL] Accept "true", "yes", "1", "false", "no", "0", and unique prefixes as input and trim input for the boolean data type

## What changes were proposed in this pull request?
This PR aims to add "true", "yes", "1", "false", "no", "0", and unique prefixes as input for the boolean data type and ignore input whitespace. Please see the following what string representations are using for the boolean type in other databases.

https://www.postgresql.org/docs/devel/datatype-boolean.html
https://docs.aws.amazon.com/redshift/latest/dg/r_Boolean_type.html

## How was this patch tested?
Added new tests to CastSuite.

Closes apache#25458 from younggyuchun/SPARK-27931.

Authored-by: younggyu chun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: younggyu chun

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/StringUtils.scala

@@ -65,12 +65,16 @@ object StringUtils extends Logging {
     "(?s)" + out.result() // (?s) enables dotall mode, causing "." to match new lines
   }
 
-  private[this] val trueStrings = Set("t", "true", "y", "yes", "1").map(UTF8String.fromString)
-  private[this] val falseStrings = Set("f", "false", "n", "no", "0").map(UTF8String.fromString)
+  // "true", "yes", "1", "false", "no", "0", and unique prefixes of these strings are accepted.
+  private[this] val trueStrings =
+    Set("true", "tru", "tr", "t", "yes", "ye", "y", "on", "1").map(UTF8String.fromString)
+
+  private[this] val falseStrings =
+    Set("false", "fals", "fal", "fa", "f", "no", "n", "off", "of", "0").map(UTF8String.fromString)
 
   // scalastyle:off caselocale
-  def isTrueString(s: UTF8String): Boolean = trueStrings.contains(s.toLowerCase)
-  def isFalseString(s: UTF8String): Boolean = falseStrings.contains(s.toLowerCase)
+  def isTrueString(s: UTF8String): Boolean = trueStrings.contains(s.toLowerCase.trim())
+  def isFalseString(s: UTF8String): Boolean = falseStrings.contains(s.toLowerCase.trim())
   // scalastyle:on caselocale
 
   /**

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala

@@ -819,20 +819,34 @@ class CastSuite extends SparkFunSuite with ExpressionEvalHelper {
   }
 
   test("cast string to boolean") {
-    checkCast("t", true)
     checkCast("true", true)
+    checkCast("tru", true)
+    checkCast("tr", true)
+    checkCast("t", true)
     checkCast("tRUe", true)
-    checkCast("y", true)
+    checkCast("    tRue   ", true)
+    checkCast("    tRu   ", true)
     checkCast("yes", true)
+    checkCast("ye", true)
+    checkCast("y", true)
     checkCast("1", true)
+    checkCast("on", true)
 
-    checkCast("f", false)
     checkCast("false", false)
-    checkCast("FAlsE", false)
-    checkCast("n", false)
+    checkCast("fals", false)
+    checkCast("fal", false)
+    checkCast("fa", false)
+    checkCast("f", false)
+    checkCast("    fAlse    ", false)
+    checkCast("    fAls    ", false)
+    checkCast("    FAlsE    ", false)
     checkCast("no", false)
+    checkCast("n", false)
     checkCast("0", false)
+    checkCast("off", false)
+    checkCast("of", false)
 
+    checkEvaluation(cast("o", BooleanType), null)
     checkEvaluation(cast("abc", BooleanType), null)
     checkEvaluation(cast("", BooleanType), null)
   }

sql/core/src/test/resources/sql-tests/inputs/pgSQL/boolean.sql

@@ -22,7 +22,6 @@ SELECT false AS `false`;
 
 SELECT boolean('t') AS true;
 
--- [SPARK-27931] Trim the string when cast string type to boolean type
 SELECT boolean('   f           ') AS `false`;
 
 SELECT boolean('true') AS true;
@@ -49,12 +48,10 @@ SELECT boolean('no') AS `false`;
 -- [SPARK-27923] PostgreSQL does not accept 'nay' but Spark SQL accepts it and sets it to NULL
 SELECT boolean('nay') AS error;
 
--- [SPARK-27931] Accept 'on' and 'off' as input for boolean data type
 SELECT boolean('on') AS true;
 
 SELECT boolean('off') AS `false`;
 
--- [SPARK-27931] Accept unique prefixes thereof
 SELECT boolean('of') AS `false`;
 
 -- [SPARK-27923] PostgreSQL does not accept 'o' but Spark SQL accepts it and sets it to NULL
@@ -101,7 +98,7 @@ SELECT boolean('f') <= boolean('t') AS true;
 
 -- explicit casts to/from text
 SELECT boolean(string('TrUe')) AS true, boolean(string('fAlse')) AS `false`;
--- [SPARK-27931] Trim the string when cast to boolean type
+
 SELECT boolean(string('    true   ')) AS true,
        boolean(string('     FALSE')) AS `false`;
 SELECT string(boolean(true)) AS true, string(boolean(false)) AS `false`;

sql/core/src/test/resources/sql-tests/results/pgSQL/boolean.sql.out

@@ -39,7 +39,7 @@ SELECT boolean('   f           ') AS `false`
 -- !query 4 schema
 struct<false:boolean>
 -- !query 4 output
-NULL
+false
 
 
 -- !query 5
@@ -127,23 +127,23 @@ SELECT boolean('on') AS true
 -- !query 15 schema
 struct<true:boolean>
 -- !query 15 output
-NULL
+true
 
 
 -- !query 16
 SELECT boolean('off') AS `false`
 -- !query 16 schema
 struct<false:boolean>
 -- !query 16 output
-NULL
+false
 
 
 -- !query 17
 SELECT boolean('of') AS `false`
 -- !query 17 schema
 struct<false:boolean>
 -- !query 17 output
-NULL
+false
 
 
 -- !query 18
@@ -296,7 +296,7 @@ SELECT boolean(string('    true   ')) AS true,
 -- !query 36 schema
 struct<true:boolean,false:boolean>
 -- !query 36 output
-NULL	NULL
+true	false
 
 
 -- !query 37