[SPARK-49611][SQL] Introduce TVF collations() & remove the `SHOW CO…

…LLATIONS` command

### What changes were proposed in this pull request?
The pr aims to
- introduce `TVF` `collations()`.
- remove the `SHOW COLLATIONS` command.

### Why are the changes needed?
Based on cloud-fan's suggestion: apache#47364 (comment)
I believe that after this, we can do many things based on it, such as `filtering` and `querying` based on `LANGUAGE` or `COUNTRY`, etc. eg:
```sql
SELECT * FROM collations() WHERE LANGUAGE like '%Chinese%';
```

### Does this PR introduce _any_ user-facing change?
Yes, provide a new TVF `collations()` for end-users.

### How was this patch tested?
- Add new UT.
- Pass GA.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes apache#48087 from panbingkun/SPARK-49611.

Lead-authored-by: panbingkun <panbingkun@baidu.com>
Co-authored-by: panbingkun <pbk1982@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

docs/sql-ref-ansi-compliance.md

@@ -442,7 +442,6 @@ Below is a list of all the keywords in Spark SQL.
 |CODEGEN|non-reserved|non-reserved|non-reserved|
 |COLLATE|reserved|non-reserved|reserved|
 |COLLATION|reserved|non-reserved|reserved|
-|COLLATIONS|reserved|non-reserved|reserved|
 |COLLECTION|non-reserved|non-reserved|non-reserved|
 |COLUMN|reserved|non-reserved|reserved|
 |COLUMNS|non-reserved|non-reserved|non-reserved|

sql/api/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBaseLexer.g4

@@ -162,7 +162,6 @@ CLUSTERED: 'CLUSTERED';
 CODEGEN: 'CODEGEN';
 COLLATE: 'COLLATE';
 COLLATION: 'COLLATION';
-COLLATIONS: 'COLLATIONS';
 COLLECTION: 'COLLECTION';
 COLUMN: 'COLUMN';
 COLUMNS: 'COLUMNS';

sql/api/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBaseParser.g4

@@ -268,7 +268,6 @@ statement
     | SHOW PARTITIONS identifierReference partitionSpec?               #showPartitions
     | SHOW identifier? FUNCTIONS ((FROM | IN) ns=identifierReference)?
         (LIKE? (legacy=multipartIdentifier | pattern=stringLit))?      #showFunctions
-    | SHOW COLLATIONS (LIKE? pattern=stringLit)?                       #showCollations
     | SHOW CREATE TABLE identifierReference (AS SERDE)?                #showCreateTable
     | SHOW CURRENT namespace                                           #showCurrentNamespace
     | SHOW CATALOGS (LIKE? pattern=stringLit)?                            #showCatalogs
@@ -1868,7 +1867,6 @@ nonReserved
     | CODEGEN
     | COLLATE
     | COLLATION
-    | COLLATIONS
     | COLLECTION
     | COLUMN
     | COLUMNS

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala

@@ -1158,6 +1158,7 @@ object TableFunctionRegistry {
     generator[PosExplode]("posexplode"),
     generator[PosExplode]("posexplode_outer", outer = true),
     generator[Stack]("stack"),
+    generator[Collations]("collations"),
     generator[SQLKeywords]("sql_keywords"),
     generator[VariantExplode]("variant_explode"),
     generator[VariantExplode]("variant_explode_outer", outer = true)

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala

@@ -24,7 +24,6 @@ import java.util.concurrent.TimeUnit
 import javax.annotation.concurrent.GuardedBy
 
 import scala.collection.mutable
-import scala.jdk.CollectionConverters.CollectionHasAsScala
 import scala.util.{Failure, Success, Try}
 
 import com.google.common.cache.{Cache, CacheBuilder}
@@ -40,8 +39,7 @@ import org.apache.spark.sql.catalyst.expressions.{Alias, Cast, Expression, Expre
 import org.apache.spark.sql.catalyst.parser.{CatalystSqlParser, ParserInterface}
 import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project, SubqueryAlias, View}
 import org.apache.spark.sql.catalyst.trees.CurrentOrigin
-import org.apache.spark.sql.catalyst.util.{CharVarcharUtils, CollationFactory, StringUtils}
-import org.apache.spark.sql.catalyst.util.CollationFactory.CollationMeta
+import org.apache.spark.sql.catalyst.util.{CharVarcharUtils, StringUtils}
 import org.apache.spark.sql.connector.catalog.CatalogManager
 import org.apache.spark.sql.connector.catalog.CatalogManager.SESSION_CATALOG_NAME
 import org.apache.spark.sql.errors.{QueryCompilationErrors, QueryExecutionErrors}
@@ -1901,17 +1899,6 @@ class SessionCatalog(
       .filter(isTemporaryFunction)
   }
 
-  /**
-   * List all built-in collations with the given pattern.
-   */
-  def listCollations(pattern: Option[String]): Seq[CollationMeta] = {
-    val collationIdentifiers = CollationFactory.listCollations().asScala.toSeq
-    val filteredCollationNames = StringUtils.filterPattern(
-      collationIdentifiers.map(_.getName), pattern.getOrElse("*")).toSet
-    collationIdentifiers.filter(ident => filteredCollationNames.contains(ident.getName)).map(
-      CollationFactory.loadCollationMeta)
-  }
-
   // -----------------
   // | Other methods |
   // -----------------

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala

@@ -18,6 +18,7 @@
 package org.apache.spark.sql.catalyst.expressions
 
 import scala.collection.mutable
+import scala.jdk.CollectionConverters.CollectionHasAsScala
 
 import org.apache.spark.sql.Row
 import org.apache.spark.sql.catalyst.{CatalystTypeConverters, InternalRow}
@@ -28,7 +29,7 @@ import org.apache.spark.sql.catalyst.expressions.codegen._
 import org.apache.spark.sql.catalyst.expressions.codegen.Block._
 import org.apache.spark.sql.catalyst.plans.logical.{FunctionSignature, InputParameter}
 import org.apache.spark.sql.catalyst.trees.TreePattern.{GENERATOR, TreePattern}
-import org.apache.spark.sql.catalyst.util.{ArrayData, MapData}
+import org.apache.spark.sql.catalyst.util.{ArrayData, CollationFactory, MapData}
 import org.apache.spark.sql.catalyst.util.SQLKeywordUtils._
 import org.apache.spark.sql.errors.{QueryCompilationErrors, QueryExecutionErrors}
 import org.apache.spark.sql.internal.SQLConf
@@ -618,3 +619,44 @@ case class SQLKeywords() extends LeafExpression with Generator with CodegenFallb
 
   override def prettyName: String = "sql_keywords"
 }
+
+@ExpressionDescription(
+  usage = """_FUNC_() - Get all of the Spark SQL string collations""",
+  examples = """
+    Examples:
+      > SELECT * FROM _FUNC_() WHERE NAME = 'UTF8_BINARY';
+       SYSTEM  BUILTIN  UTF8_BINARY NULL  NULL  ACCENT_SENSITIVE  CASE_SENSITIVE  NO_PAD  NULL
+  """,
+  since = "4.0.0",
+  group = "generator_funcs")
+case class Collations() extends LeafExpression with Generator with CodegenFallback {
+  override def elementSchema: StructType = new StructType()
+    .add("CATALOG", StringType, nullable = false)
+    .add("SCHEMA", StringType, nullable = false)
+    .add("NAME", StringType, nullable = false)
+    .add("LANGUAGE", StringType)
+    .add("COUNTRY", StringType)
+    .add("ACCENT_SENSITIVITY", StringType, nullable = false)
+    .add("CASE_SENSITIVITY", StringType, nullable = false)
+    .add("PAD_ATTRIBUTE", StringType, nullable = false)
+    .add("ICU_VERSION", StringType)
+
+  override def eval(input: InternalRow): IterableOnce[InternalRow] = {
+    CollationFactory.listCollations().asScala.map(CollationFactory.loadCollationMeta).map { m =>
+      InternalRow(
+        UTF8String.fromString(m.catalog),
+        UTF8String.fromString(m.schema),
+        UTF8String.fromString(m.collationName),
+        UTF8String.fromString(m.language),
+        UTF8String.fromString(m.country),
+        UTF8String.fromString(
+          if (m.accentSensitivity) "ACCENT_SENSITIVE" else "ACCENT_INSENSITIVE"),
+        UTF8String.fromString(
+          if (m.caseSensitivity) "CASE_SENSITIVE" else "CASE_INSENSITIVE"),
+        UTF8String.fromString(m.padAttribute),
+        UTF8String.fromString(m.icuVersion))
+    }
+  }
+
+  override def prettyName: String = "collations"
+}

sql/catalyst/src/test/resources/ansi-sql-2016-reserved-keywords.txt

@@ -48,7 +48,6 @@ CLOSE
 COALESCE
 COLLATE
 COLLATION
-COLLATIONS
 COLLECT
 COLUMN
 COMMIT

sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala

@@ -1096,16 +1096,4 @@ class SparkSqlAstBuilder extends AstBuilder {
       withIdentClause(ctx.identifierReference(), UnresolvedNamespace(_)),
       cleanedProperties)
   }
-
-  /**
-   * Create a [[ShowCollationsCommand]] command.
-   * Expected format:
-   * {{{
-   *   SHOW COLLATIONS (LIKE? pattern=stringLit)?;
-   * }}}
-   */
-  override def visitShowCollations(ctx: ShowCollationsContext): LogicalPlan = withOrigin(ctx) {
-    val pattern = Option(ctx.pattern).map(x => string(visitStringLit(x)))
-    ShowCollationsCommand(pattern)
-  }
 }

sql/core/src/test/resources/sql-tests/results/ansi/keywords.sql.out

@@ -48,7 +48,6 @@ CLUSTERED	false
 CODEGEN	false
 COLLATE	true
 COLLATION	true
-COLLATIONS	true
 COLLECTION	false
 COLUMN	true
 COLUMNS	false
@@ -384,7 +383,6 @@ CAST
 CHECK
 COLLATE
 COLLATION
-COLLATIONS
 COLUMN
 CONSTRAINT
 CREATE

sql/core/src/test/resources/sql-tests/results/keywords.sql.out

@@ -48,7 +48,6 @@ CLUSTERED	false
 CODEGEN	false
 COLLATE	false
 COLLATION	false
-COLLATIONS	false
 COLLECTION	false
 COLUMN	false
 COLUMNS	false

sql/core/src/test/scala/org/apache/spark/sql/CollationSuite.scala

@@ -1625,38 +1625,38 @@ class CollationSuite extends DatasourceV2SQLBase with AdaptiveSparkPlanHelper {
     }
   }
 
-  test("show collations") {
-    assert(sql("SHOW COLLATIONS").collect().length >= 562)
+  test("TVF collations()") {
+    assert(sql("SELECT * FROM collations()").collect().length >= 562)
 
     // verify that the output ordering is as expected (UTF8_BINARY, UTF8_LCASE, etc.)
-    val df = sql("SHOW COLLATIONS").limit(10)
+    val df = sql("SELECT * FROM collations() limit 10")
     checkAnswer(df,
       Seq(Row("SYSTEM", "BUILTIN", "UTF8_BINARY", null, null,
         "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", null),
-      Row("SYSTEM", "BUILTIN", "UTF8_LCASE", null, null,
-        "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", null),
-      Row("SYSTEM", "BUILTIN", "UNICODE", "", "",
-        "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
-      Row("SYSTEM", "BUILTIN", "UNICODE_AI", "", "",
-        "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
-      Row("SYSTEM", "BUILTIN", "UNICODE_CI", "", "",
-        "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
-     Row("SYSTEM", "BUILTIN", "UNICODE_CI_AI", "", "",
-       "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
-     Row("SYSTEM", "BUILTIN", "af", "Afrikaans", "",
-       "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
-     Row("SYSTEM", "BUILTIN", "af_AI", "Afrikaans", "",
-       "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
-     Row("SYSTEM", "BUILTIN", "af_CI", "Afrikaans", "",
-       "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
-     Row("SYSTEM", "BUILTIN", "af_CI_AI", "Afrikaans", "",
-        "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0")))
-
-    checkAnswer(sql("SHOW COLLATIONS LIKE '*UTF8_BINARY*'"),
+        Row("SYSTEM", "BUILTIN", "UTF8_LCASE", null, null,
+          "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", null),
+        Row("SYSTEM", "BUILTIN", "UNICODE", "", "",
+          "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "UNICODE_AI", "", "",
+          "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "UNICODE_CI", "", "",
+          "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "UNICODE_CI_AI", "", "",
+          "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "af", "Afrikaans", "",
+          "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "af_AI", "Afrikaans", "",
+          "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "af_CI", "Afrikaans", "",
+          "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "af_CI_AI", "Afrikaans", "",
+          "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0")))
+
+    checkAnswer(sql("SELECT * FROM collations() WHERE NAME LIKE '%UTF8_BINARY%'"),
       Row("SYSTEM", "BUILTIN", "UTF8_BINARY", null, null,
         "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", null))
 
-    checkAnswer(sql("SHOW COLLATIONS '*zh_Hant_HKG*'"),
+    checkAnswer(sql("SELECT * FROM collations() WHERE NAME LIKE '%zh_Hant_HKG%'"),
       Seq(Row("SYSTEM", "BUILTIN", "zh_Hant_HKG", "Chinese", "Hong Kong SAR China",
         "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
         Row("SYSTEM", "BUILTIN", "zh_Hant_HKG_AI", "Chinese", "Hong Kong SAR China",
@@ -1665,5 +1665,36 @@ class CollationSuite extends DatasourceV2SQLBase with AdaptiveSparkPlanHelper {
           "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
         Row("SYSTEM", "BUILTIN", "zh_Hant_HKG_CI_AI", "Chinese", "Hong Kong SAR China",
           "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0")))
+
+    checkAnswer(sql("SELECT * FROM collations() WHERE COUNTRY = 'Singapore'"),
+      Seq(Row("SYSTEM", "BUILTIN", "zh_Hans_SGP", "Chinese", "Singapore",
+        "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "zh_Hans_SGP_AI", "Chinese", "Singapore",
+          "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "zh_Hans_SGP_CI", "Chinese", "Singapore",
+          "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "zh_Hans_SGP_CI_AI", "Chinese", "Singapore",
+          "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0")))
+
+    checkAnswer(sql("SELECT * FROM collations() WHERE LANGUAGE = 'English' " +
+      "and COUNTRY = 'United States'"),
+      Seq(Row("SYSTEM", "BUILTIN", "en_USA", "English", "United States",
+        "ACCENT_SENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "en_USA_AI", "English", "United States",
+          "ACCENT_SENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "en_USA_CI", "English", "United States",
+          "ACCENT_INSENSITIVE", "CASE_SENSITIVE", "NO_PAD", "75.1.0.0"),
+        Row("SYSTEM", "BUILTIN", "en_USA_CI_AI", "English", "United States",
+          "ACCENT_INSENSITIVE", "CASE_INSENSITIVE", "NO_PAD", "75.1.0.0")))
+
+    checkAnswer(sql("SELECT NAME, LANGUAGE, ACCENT_SENSITIVITY, CASE_SENSITIVITY " +
+      "FROM collations() WHERE COUNTRY = 'United States'"),
+      Seq(Row("en_USA", "English", "ACCENT_SENSITIVE", "CASE_SENSITIVE"),
+        Row("en_USA_AI", "English", "ACCENT_SENSITIVE", "CASE_INSENSITIVE"),
+        Row("en_USA_CI", "English", "ACCENT_INSENSITIVE", "CASE_SENSITIVE"),
+        Row("en_USA_CI_AI", "English", "ACCENT_INSENSITIVE", "CASE_INSENSITIVE")))
+
+    checkAnswer(sql("SELECT NAME FROM collations() WHERE ICU_VERSION is null"),
+      Seq(Row("UTF8_BINARY"), Row("UTF8_LCASE")))
   }
 }