Add PPL describe command

docs/PPL-Correlation-command.md

@@ -1,5 +1,8 @@
 ## PPL Correlation Command
 
+> This is an experimental command - it may be removed in future versions
+
+
 ## Overview
 
 In the past year OpenSearch Observability & security teams have been busy with many aspects of improving data monitoring and visibility.
@@ -262,6 +265,8 @@ The new correlation command is actually a ‘hidden’ join command therefore th
 
 Catalyst engine will optimize this query according to the most efficient join ordering.
 
+> This is an experimental command - it may be removed in future versions
+
 * * *
 
 ## Appendix

integ-test/src/integration/scala/org/opensearch/flint/spark/ppl/FlintSparkPPLBasicITSuite.scala

@@ -6,9 +6,11 @@
 package org.opensearch.flint.spark.ppl
 
 import org.apache.spark.sql.{QueryTest, Row}
-import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedRelation, UnresolvedStar}
+import org.apache.spark.sql.catalyst.TableIdentifier
+import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedRelation, UnresolvedStar, UnresolvedTableOrView}
 import org.apache.spark.sql.catalyst.expressions.{Ascending, Literal, SortOrder}
 import org.apache.spark.sql.catalyst.plans.logical._
+import org.apache.spark.sql.execution.command.DescribeTableCommand
 import org.apache.spark.sql.streaming.StreamTest
 
 class FlintSparkPPLBasicITSuite
@@ -36,6 +38,45 @@ class FlintSparkPPLBasicITSuite
     }
   }
 
+  test("describe table query test") {
+    val testTableQuoted = "`spark_catalog`.`default`.`flint_ppl_test`"
+    Seq(testTable, testTableQuoted).foreach { table =>
+      val frame = sql(s"""
+           describe flint_ppl_test
+           """.stripMargin)
+
+      // Retrieve the results
+      val results: Array[Row] = frame.collect()
+      // Define the expected results
+      val expectedResults: Array[Row] = Array(
+        Row("name", "string", null),
+        Row("age", "int", null),
+        Row("state", "string", null),
+        Row("country", "string", null),
+        Row("year", "int", null),
+        Row("month", "int", null),
+        Row("# Partition Information", "", ""),
+        Row("# col_name", "data_type", "comment"),
+        Row("year", "int", null),
+        Row("month", "int", null))
+      // Compare the results
+      implicit val rowOrdering: Ordering[Row] = Ordering.by[Row, String](_.getAs[String](0))
+      assert(results.sorted.sameElements(expectedResults.sorted))
+      // Retrieve the logical plan
+      val logicalPlan: LogicalPlan =
+        frame.queryExecution.commandExecuted.asInstanceOf[CommandResult].commandLogicalPlan
+      // Define the expected logical plan
+      val expectedPlan: LogicalPlan =
+        DescribeTableCommand(
+          TableIdentifier("flint_ppl_test"),
+          Map.empty[String, String],
+          isExtended = false,
+          output = DescribeRelation.getOutputAttrs)
+      // Compare the two plans
+      comparePlans(logicalPlan, expectedPlan, checkAnalysis = false)
+    }
+  }
+
   test("create ppl simple query test") {
     val testTableQuoted = "`spark_catalog`.`default`.`flint_ppl_test`"
     Seq(testTable, testTableQuoted).foreach { table =>
@@ -208,7 +249,7 @@ class FlintSparkPPLBasicITSuite
         val sortedPlan: LogicalPlan =
           Sort(Seq(SortOrder(UnresolvedAttribute("age"), Ascending)), global = true, limitPlan)
 
-        val expectedPlan = Project(Seq(UnresolvedStar(None)), sortedPlan);
+        val expectedPlan = Project(Seq(UnresolvedStar(None)), sortedPlan)
         // Compare the two plans
         assert(compareByString(expectedPlan) === compareByString(logicalPlan))
     }

ppl-spark-integration/README.md

@@ -221,8 +221,8 @@ Next tasks ahead will resolve this:
 
 This section describes the next steps planned for enabling additional commands and gamer translation.
 
-#### Supported
-The next samples of PPL queries are currently supported:
+#### Example PPL Queries
+See the next samples of PPL queries :
 
 **Fields**
  - `source = table`
@@ -272,31 +272,15 @@ Limitation: Overriding existing field is unsupported, following queries throw ex
 - `source = table | stats sum(productsAmount) by span(transactionDate, 1d) as age_date | sort age_date`
 - `source = table | stats sum(productsAmount) by span(transactionDate, 1w) as age_date, productId`
 
-> For additional details, review [FlintSparkPPLTimeWindowITSuite.scala](../integ-test/src/test/scala/org/opensearch/flint/spark/ppl/FlintSparkPPLTimeWindowITSuite.scala)
-
-#### Supported Commands:
- - `search` - [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/search.rst)  
- - `where`  - [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/where.rst)  
- - `fields` - [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/fields.rst)  
- - `eval`   - [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/eval.rst)
- - `head`   - [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/head.rst)
- - `stats`  - [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/stats.rst) (supports AVG, COUNT, DISTINCT_COUNT, MAX, MIN and SUM aggregation functions)
- - `sort` -   [See details](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/sort.rst)
- - `correlation` - [See details](../docs/PPL-Correlation-command.md)
-
-> For additional details, review [Integration Tests](../integ-test/src/test/scala/org/opensearch/flint/spark/)
-
 ---
 
-#### Planned Support
+For additional details on PPL commands - view [PPL Commands Docs](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/index.rst)
 
- - support the `explain` command to return the explained PPL query logical plan and expected execution plan
+For additional details on Spark PPL commands project, see [PPL Project](https://github.com/orgs/opensearch-project/projects/214/views/2)
+For additional details on Spark PPL commands support campaign, see [PPL Commands Campaign](https://github.com/opensearch-project/opensearch-spark/issues/408)
+
+#### Experimental Commands:
+ - `correlation` - [See details](../docs/PPL-Correlation-command.md)
 
- - attend [sort](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/sort.rst) partially supported, missing capability to sort by alias field (span like or aggregation)
- - attend `alias` - partially supported, missing capability to sort by / group-by alias field name 
+> This is an experimental command - it may be removed in future versions
 
- - add [conditions](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/functions/condition.rst) support
- - add [top](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/top.rst) support
- - add [cast](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/functions/conversion.rst) support
- - add [math](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/functions/math.rst) support
- - add [deduplicate](https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/dedup.rst) support

ppl-spark-integration/src/main/antlr4/OpenSearchPPLParser.g4

@@ -27,6 +27,7 @@ queryStatement
 // commands
 pplCommands
    : searchCommand
+   | describeCommand
    ;
 
 commands

ppl-spark-integration/src/main/java/org/opensearch/sql/ast/tree/DescribeRelation.java

@@ -0,0 +1,17 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.ast.tree;
+
+import org.opensearch.sql.ast.expression.UnresolvedExpression;
+
+/**
+ * Extend Relation to describe the table itself
+ */
+public class DescribeRelation extends Relation{
+    public DescribeRelation(UnresolvedExpression tableName) {
+        super(tableName);
+    }
+}

ppl-spark-integration/src/main/java/org/opensearch/sql/ppl/CatalystQueryPlanVisitor.java

@@ -5,6 +5,7 @@
 
 package org.opensearch.sql.ppl;
 
+import org.apache.spark.sql.catalyst.TableIdentifier;
 import org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute$;
 import org.apache.spark.sql.catalyst.analysis.UnresolvedRelation;
 import org.apache.spark.sql.catalyst.analysis.UnresolvedStar$;
@@ -13,8 +14,10 @@
 import org.apache.spark.sql.catalyst.expressions.Predicate;
 import org.apache.spark.sql.catalyst.expressions.SortOrder;
 import org.apache.spark.sql.catalyst.plans.logical.Aggregate;
+import org.apache.spark.sql.catalyst.plans.logical.DescribeRelation$;
 import org.apache.spark.sql.catalyst.plans.logical.Limit;
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan;
+import org.apache.spark.sql.execution.command.DescribeTableCommand;
 import org.apache.spark.sql.types.DataTypes;
 import org.apache.spark.sql.util.CaseInsensitiveStringMap;
 import org.opensearch.sql.ast.AbstractNodeVisitor;
@@ -46,6 +49,7 @@
 import org.opensearch.sql.ast.tree.Aggregation;
 import org.opensearch.sql.ast.tree.Correlation;
 import org.opensearch.sql.ast.tree.Dedupe;
+import org.opensearch.sql.ast.tree.DescribeRelation;
 import org.opensearch.sql.ast.tree.Eval;
 import org.opensearch.sql.ast.tree.Filter;
 import org.opensearch.sql.ast.tree.Head;
@@ -59,6 +63,7 @@
 import org.opensearch.sql.ppl.utils.ComparatorTransformer;
 import org.opensearch.sql.ppl.utils.SortUtils;
 import scala.Option;
+import scala.Option$;
 import scala.collection.Seq;
 
 import java.util.ArrayList;
@@ -107,6 +112,26 @@ public LogicalPlan visitExplain(Explain node, CatalystPlanContext context) {
 
     @Override
     public LogicalPlan visitRelation(Relation node, CatalystPlanContext context) {
+        if (node instanceof DescribeRelation) {
+            TableIdentifier identifier;
+            if (node.getTableQualifiedName().getParts().size() == 1) {
+                identifier = new TableIdentifier(node.getTableQualifiedName().getParts().get(0));
+            } else if (node.getTableQualifiedName().getParts().size() == 2) {
+                identifier = new TableIdentifier(
+                        node.getTableQualifiedName().getParts().get(1),
+                        Option$.MODULE$.apply(node.getTableQualifiedName().getParts().get(0)));
+            } else {
+                throw new IllegalArgumentException("Invalid table name: " + node.getTableQualifiedName()
+                        + " Syntax: [ database_name. ] table_name");
+            }
+            return context.with(
+                    new DescribeTableCommand(
+                            identifier,
+                            scala.collection.immutable.Map$.MODULE$.<String, String>empty(),
+                            false,
+                            DescribeRelation$.MODULE$.getOutputAttrs()));
+        }
+        //regular sql algebraic relations 
         node.getTableName().forEach(t ->
                 // Resolving the qualifiedName which is composed of a datasource.schema.table
                 context.with(new UnresolvedRelation(seq(of(t.split("\\."))), CaseInsensitiveStringMap.empty(), false))

ppl-spark-integration/src/main/java/org/opensearch/sql/ppl/parser/AstBuilder.java

@@ -28,6 +28,7 @@
 import org.opensearch.sql.ast.tree.Aggregation;
 import org.opensearch.sql.ast.tree.Correlation;
 import org.opensearch.sql.ast.tree.Dedupe;
+import org.opensearch.sql.ast.tree.DescribeRelation;
 import org.opensearch.sql.ast.tree.Eval;
 import org.opensearch.sql.ast.tree.Filter;
 import org.opensearch.sql.ast.tree.Head;
@@ -97,7 +98,7 @@ public UnresolvedPlan visitDescribeCommand(OpenSearchPPLParser.DescribeCommandCo
     final Relation table = (Relation) visitTableSourceClause(ctx.tableSourceClause());
     QualifiedName tableQualifiedName = table.getTableQualifiedName();
     ArrayList<String> parts = new ArrayList<>(tableQualifiedName.getParts());
-    return new Relation(new QualifiedName(parts));
+    return new DescribeRelation(new QualifiedName(parts));
   }
 
   /** Where command. */

ppl-spark-integration/src/main/java/org/opensearch/sql/ppl/parser/AstStatementBuilder.java

@@ -15,6 +15,7 @@
 import org.opensearch.sql.ast.statement.Explain;
 import org.opensearch.sql.ast.statement.Query;
 import org.opensearch.sql.ast.statement.Statement;
+import org.opensearch.sql.ast.tree.DescribeRelation;
 import org.opensearch.sql.ast.tree.Project;
 import org.opensearch.sql.ast.tree.UnresolvedPlan;
 
@@ -78,11 +79,13 @@ public Object build() {
     }
   }
 
-  private UnresolvedPlan addSelectAll(UnresolvedPlan plan) {
-    if ((plan instanceof Project) && !((Project) plan).isExcluded()) {
-      return plan;
-    } else {
-      return new Project(ImmutableList.of(AllFields.of())).attach(plan);
+    private UnresolvedPlan addSelectAll(UnresolvedPlan plan) {
+        if ((plan instanceof Project) && !((Project) plan).isExcluded()) {
+            return plan;
+        } else if (plan instanceof DescribeRelation) {
+            return plan;
+        } else {
+            return new Project(ImmutableList.of(AllFields.of())).attach(plan);
+        }
     }
-  }
 }

ppl-spark-integration/src/test/scala/org/opensearch/flint/spark/ppl/PPLLogicalPlanBasicQueriesTranslatorTestSuite.scala

@@ -10,10 +10,12 @@ import org.opensearch.sql.ppl.{CatalystPlanContext, CatalystQueryPlanVisitor}
 import org.scalatest.matchers.should.Matchers
 
 import org.apache.spark.SparkFunSuite
+import org.apache.spark.sql.catalyst.TableIdentifier
 import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedRelation, UnresolvedStar}
 import org.apache.spark.sql.catalyst.expressions.{Ascending, AttributeReference, Descending, Literal, NamedExpression, SortOrder}
 import org.apache.spark.sql.catalyst.plans.PlanTest
 import org.apache.spark.sql.catalyst.plans.logical._
+import org.apache.spark.sql.execution.command.DescribeTableCommand
 
 class PPLLogicalPlanBasicQueriesTranslatorTestSuite
     extends SparkFunSuite
@@ -24,6 +26,45 @@ class PPLLogicalPlanBasicQueriesTranslatorTestSuite
   private val planTransformer = new CatalystQueryPlanVisitor()
   private val pplParser = new PPLSyntaxParser()
 
+  test("test error describe clause") {
+    // if successful build ppl logical plan and translate to catalyst logical plan
+    val context = new CatalystPlanContext
+    // Intercept the exception and check the message
+    val thrown = intercept[IllegalArgumentException] {
+      planTransformer.visit(plan(pplParser, "describe t.b.c.d", false), context)
+    }
+
+    // Verify the exception message
+    assert(
+      thrown.getMessage === "Invalid table name: t.b.c.d Syntax: [ database_name. ] table_name")
+  }
+
+  test("test simple describe clause") {
+    // if successful build ppl logical plan and translate to catalyst logical plan
+    val context = new CatalystPlanContext
+    val logPlan = planTransformer.visit(plan(pplParser, "describe t", false), context)
+
+    val expectedPlan = DescribeTableCommand(
+      TableIdentifier("t"),
+      Map.empty[String, String],
+      isExtended = false,
+      output = DescribeRelation.getOutputAttrs)
+    comparePlans(expectedPlan, logPlan, false)
+  }
+
+  test("test FQN table describe table clause") {
+    // if successful build ppl logical plan and translate to catalyst logical plan
+    val context = new CatalystPlanContext
+    val logPlan = planTransformer.visit(plan(pplParser, "describe catalog.t", false), context)
+
+    val expectedPlan = DescribeTableCommand(
+      TableIdentifier("t", Option("catalog")),
+      Map.empty[String, String].empty,
+      isExtended = false,
+      output = DescribeRelation.getOutputAttrs)
+    comparePlans(expectedPlan, logPlan, false)
+  }
+
   test("test simple search with only one table and no explicit fields (defaults to all fields)") {
     // if successful build ppl logical plan and translate to catalyst logical plan
     val context = new CatalystPlanContext