[SPARK-52142][SQL] Display table constraints in SHOW CREATE TABLE COMMAND

sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/constraints/BaseConstraint.java

@@ -63,12 +63,13 @@ public boolean rely() {
 
   @Override
   public String toDDL() {
+    // The validation status is not included in the DDL output as it's not part of
+    // the Spark SQL syntax for constraints.
     return String.format(
-        "CONSTRAINT %s %s %s %s %s",
+        "CONSTRAINT %s %s %s %s",
         name,
         definition(),
         enforced ? "ENFORCED" : "NOT ENFORCED",
-        validationStatus,
         rely ? "RELY" : "NORELY");
   }
 

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/ShowCreateTableExec.scala

@@ -65,7 +65,8 @@ case class ShowCreateTableExec(
   private def showTableDataColumns(table: Table, builder: StringBuilder): Unit = {
     import org.apache.spark.sql.connector.catalog.CatalogV2Implicits._
     val columns = CharVarcharUtils.getRawSchema(table.columns.asSchema, conf).fields.map(_.toDDL)
-    builder ++= concatByMultiLines(columns)
+    val constraints = table.constraints().map(_.toDDL)
+    builder ++= concatByMultiLines(columns ++ constraints)
   }
 
   private def showTableUsing(table: Table, builder: StringBuilder): Unit = {

sql/core/src/test/scala/org/apache/spark/sql/execution/command/v2/ShowCreateTableSuite.scala

@@ -181,4 +181,60 @@ class ShowCreateTableSuite extends command.ShowCreateTableSuiteBase with Command
       )
     }
   }
+
+  test("show table constraints") {
+    withNamespaceAndTable("ns", "tbl", nonPartitionCatalog) { t =>
+      withTable("other_table") {
+        sql(
+          s"""
+             |CREATE TABLE other_table (
+             |  id STRING PRIMARY KEY
+             |)
+             |USING parquet
+        """.stripMargin)
+        sql(
+          s"""
+             |CREATE TABLE $t (
+             |  a INT,
+             |  b STRING,
+             |  c STRING,
+             |  PRIMARY KEY (a),
+             |  CONSTRAINT uk_b UNIQUE (b),
+             |  CONSTRAINT fk_c FOREIGN KEY (c) REFERENCES other_table(id) RELY,
+             |  CONSTRAINT c1 CHECK (c IS NOT NULL),
+             |  CONSTRAINT c2 CHECK (a > 0)
+             |)
+             |$defaultUsing
+        """.stripMargin)
+        var showDDL = getShowCreateDDL(t)
+        val expectedDDLPrefix = Array(
+          s"CREATE TABLE $nonPartitionCatalog.ns.tbl (",
+          "a INT,",
+          "b STRING,",
+          "c STRING,",
+          "CONSTRAINT tbl_pk PRIMARY KEY (a) NOT ENFORCED NORELY,",
+          "CONSTRAINT uk_b UNIQUE (b) NOT ENFORCED NORELY,",
+          "CONSTRAINT fk_c FOREIGN KEY (c) REFERENCES other_table (id) NOT ENFORCED RELY,",
+          "CONSTRAINT c1 CHECK (c IS NOT NULL) ENFORCED NORELY,"
+        )
+        assert(showDDL === expectedDDLPrefix ++ Array(
+          "CONSTRAINT c2 CHECK (a > 0) ENFORCED NORELY)",
+          defaultUsing))
+
+        sql(s"ALTER TABLE $t ADD CONSTRAINT c3 CHECK (b IS NOT NULL) ENFORCED RELY")
+        showDDL = getShowCreateDDL(t)
+        val expectedDDLArrayWithNewConstraint = expectedDDLPrefix ++ Array(
+          "CONSTRAINT c2 CHECK (a > 0) ENFORCED NORELY,",
+          "CONSTRAINT c3 CHECK (b IS NOT NULL) ENFORCED RELY)",
+          defaultUsing
+        )
+        assert(showDDL === expectedDDLArrayWithNewConstraint)
+        sql(s"ALTER TABLE $t DROP CONSTRAINT c1")
+        showDDL = getShowCreateDDL(t)
+        val expectedDDLArrayAfterDrop = expectedDDLArrayWithNewConstraint.filterNot(
+          _.contains("c1 CHECK (c IS NOT NULL) ENFORCED NORELY"))
+        assert(showDDL === expectedDDLArrayAfterDrop)
+      }
+    }
+  }
 }