[WIP][SPARK-29887][SQL]PostgreSQL dialect: cast to smallint

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

@@ -19,15 +19,15 @@ package org.apache.spark.sql.catalyst.analysis
 
 import org.apache.spark.internal.Logging
 import org.apache.spark.sql.catalyst.expressions.Cast
-import org.apache.spark.sql.catalyst.expressions.postgreSQL.PostgreCastToBoolean
+import org.apache.spark.sql.catalyst.expressions.postgreSQL.{PostgreCastToBoolean, PostgreCastToShort}
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.rules.Rule
 import org.apache.spark.sql.internal.SQLConf
-import org.apache.spark.sql.types.{BooleanType, StringType}
+import org.apache.spark.sql.types.{BooleanType, ShortType, StringType}
 
 object PostgreSQLDialect {
   val postgreSQLDialectRules: List[Rule[LogicalPlan]] =
-    CastToBoolean ::
+    CastToBoolean :: CastToShort ::
       Nil
 
   object CastToBoolean extends Rule[LogicalPlan] with Logging {
@@ -46,4 +46,21 @@ object PostgreSQLDialect {
       }
     }
   }
+
+  object CastToShort extends Rule[LogicalPlan] with Logging {
+    override def apply(plan: LogicalPlan): LogicalPlan = {
+      // The SQL configuration `spark.sql.dialect` can be changed in runtime.
+      // To make sure the configuration is effective, we have to check it during rule execution.
+      val conf = SQLConf.get
+      if (conf.usePostgreSQLDialect) {
+        plan.transformExpressions {
+          case Cast(child, dataType, timeZoneId)
+            if child.dataType != ShortType && dataType == ShortType =>
+            PostgreCastToShort(child, timeZoneId)
+        }
+      } else {
+        plan
+      }
+    }
+  }
 }

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

@@ -507,7 +507,7 @@ abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression wit
   }
 
   // ShortConverter
-  private[this] def castToShort(from: DataType): Any => Any = from match {
+  protected[this] def castToShort(from: DataType): Any => Any = from match {
     case StringType =>
       val result = new IntWrapper()
       buildCast[UTF8String](_, s => if (s.toShort(result)) {
@@ -1363,7 +1363,7 @@ abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression wit
       (c, evPrim, evNull) => code"$evPrim = (byte) $c;"
   }
 
-  private[this] def castToShortCode(
+  protected[this] def castToShortCode(
       from: DataType,
       ctx: CodegenContext): CastFunction = from match {
     case StringType =>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/postgreSQL/PostgreCastToShort.scala

@@ -0,0 +1,87 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.spark.sql.catalyst.expressions.postgreSQL
+
+import org.apache.spark.sql.AnalysisException
+import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
+import org.apache.spark.sql.catalyst.expressions.{CastBase, Expression, TimeZoneAwareExpression}
+import org.apache.spark.sql.catalyst.expressions.codegen.Block._
+import org.apache.spark.sql.catalyst.expressions.codegen.CodegenContext
+import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.types.UTF8String
+import org.apache.spark.unsafe.types.UTF8String.IntWrapper
+
+case class PostgreCastToShort(child: Expression, timeZoneId: Option[String])
+  extends CastBase {
+
+  override protected def ansiEnabled =
+    throw new UnsupportedOperationException("PostgreSQL dialect doesn't support ansi mode")
+
+  override def withTimeZone(timeZoneId: String): TimeZoneAwareExpression =
+    copy(timeZoneId = Option(timeZoneId))
+
+  override def checkInputDataTypes(): TypeCheckResult = child.dataType match {
+    case StringType | IntegerType | LongType | ByteType | FloatType | DoubleType | NullType =>
+      TypeCheckResult.TypeCheckSuccess
+    case _: DecimalType => TypeCheckResult.TypeCheckSuccess
+    case _ =>
+      TypeCheckResult.TypeCheckFailure(s"cannot cast type ${child.dataType} to short")
+  }
+
+  override def castToShort(from: DataType): Any => Any = from match {
+    case StringType =>
+      val result = new IntWrapper()
+      buildCast[UTF8String](_, s => if (s.toShort(result)) {
+        result.value.toShort
+      } else {
+        throw new AnalysisException(s"invalid input syntax for integer: $s")
+      })
+    case x: NumericType =>
+      b => x.numeric.asInstanceOf[Numeric[Any]].toInt(b).toShort
+  }
+
+  def castDecimalToIntegralTypeCode(ctx: CodegenContext, integralType: String): CastFunction = {
+      (c, evPrim, evNull) => code"$evPrim = $c.to${integralType.capitalize}();"
+  }
+
+  override def castToShortCode(from: DataType, ctx: CodegenContext): CastFunction = from match {
+    case StringType =>
+      val wrapper = ctx.freshVariable("intWrapper", classOf[UTF8String.IntWrapper])
+      (c, evPrim, evNull) =>
+        code"""
+          UTF8String.IntWrapper $wrapper = new UTF8String.IntWrapper();
+          if ($c.toShort($wrapper)) {
+            $evPrim = (short) $wrapper.value;
+          } else {
+            throw new AnalysisException("invalid input syntax for integer: $c")
+          }
+          $wrapper = null;
+        """
+
+    case DecimalType() => castDecimalToIntegralTypeCode(ctx, "short")
+    case _: NumericType =>
+      (c, evPrim, evNull) => code"$evPrim = (short) $c;"
+  }
+
+  override def dataType: DataType = ShortType
+
+  override def nullable: Boolean = child.nullable
+
+  override def toString: String = s"PostgreCastToShort($child as ${dataType.simpleString})"
+
+  override def sql: String = s"CAST(${child.sql} AS ${dataType.sql})"
+}