Adding Spark Core config to control maximum number of fields

core/src/main/scala/org/apache/spark/internal/config/package.scala

@@ -633,4 +633,14 @@ package object config {
       .stringConf
       .toSequence
       .createWithDefault(Nil)
+
+  private[spark] val MAX_TO_STRING_FIELDS =
+    ConfigBuilder("spark.debug.maxToStringFields")
+      .internal()
+      .doc("Maximum number of fields of sequence-like entries that can be converted to strings " +
+        "in debug output. Any elements beyond the limit will be dropped and replaced by a" +
+        """ "... N more fields" placeholder. The config will be removed in Spark 3.0.""")
+      .intConf
+      .checkValue(v => v > 0, "The value should be a positive integer.")
+      .createWithDefault(25)
 }

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

@@ -23,6 +23,7 @@ import java.util.concurrent.atomic.AtomicBoolean
 
 import org.apache.spark.SparkEnv
 import org.apache.spark.internal.Logging
+import org.apache.spark.internal.config
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types.{NumericType, StringType}
@@ -174,15 +175,14 @@ package object util extends Logging {
   /**
    * The performance overhead of creating and logging strings for wide schemas can be large. To
    * limit the impact, we bound the number of fields to include by default. This can be overridden
-   * by setting the 'spark.debug.maxToStringFields' conf in SparkEnv.
+   * by setting the 'spark.debug.maxToStringFields' conf in SparkEnv or by settings the SQL config
+   * `spark.sql.debug.maxToStringFields`.
    */
-  val DEFAULT_MAX_TO_STRING_FIELDS = 25
-
-  private[spark] def maxNumToStringFields = {
+  private[spark] def maxNumToStringFields: Int = {
     val legacyLimit = if (SparkEnv.get != null) {
-      SparkEnv.get.conf.getInt("spark.debug.maxToStringFields", DEFAULT_MAX_TO_STRING_FIELDS)
+      SparkEnv.get.conf.get(config.MAX_TO_STRING_FIELDS)
     } else {
-      DEFAULT_MAX_TO_STRING_FIELDS
+      config.MAX_TO_STRING_FIELDS.defaultValue.get
     }
     val sqlConfLimit = SQLConf.get.maxToStringFields