Redshift: use zstd compression encoding instead text255 with the colu…

…mns for enum fields (#215)

Currently, we make the compression encoding of the columns for enum fields text255.
However, text255 doesn't allow to alter the column therefore we get exception while
trying to resize the column. In order to solve this problem, we decided to use zstd
compression encoding with enum fields as well.

Encoding of the newly created columns for enum fields will be zstd after this change
however compression encoding of the existing columns won't be updated after this
change and we will continue to get exception when those columns are tried to be resized.
Those exception will be caught and ignored in RDB Loader.

modules/core/src/main/scala/com.snowplowanalytics/iglu.schemaddl/redshift/ShredModelEntry.scala

@@ -35,11 +35,9 @@ case class ShredModelEntry(
     .flatMap(_.apply(subSchema))
     .getOrElse(ShredModelEntry.ColumnType.RedshiftVarchar(ShredModelEntry.VARCHAR_SIZE))
 
-  lazy val compressionEncoding: ShredModelEntry.CompressionEncoding = (subSchema.`enum`, columnType) match {
-    case (Some(_), ShredModelEntry.ColumnType.RedshiftVarchar(size)) if size <= 255 =>
-      ShredModelEntry.CompressionEncoding.Text255Encoding
-    case (_, ShredModelEntry.ColumnType.RedshiftBoolean) => ShredModelEntry.CompressionEncoding.RunLengthEncoding
-    case (_, ShredModelEntry.ColumnType.RedshiftDouble) => ShredModelEntry.CompressionEncoding.RawEncoding
+  lazy val compressionEncoding: ShredModelEntry.CompressionEncoding = columnType match {
+    case ShredModelEntry.ColumnType.RedshiftBoolean => ShredModelEntry.CompressionEncoding.RunLengthEncoding
+    case ShredModelEntry.ColumnType.RedshiftDouble => ShredModelEntry.CompressionEncoding.RawEncoding
     case _ => ShredModelEntry.CompressionEncoding.ZstdEncoding
   }
 
@@ -169,7 +167,6 @@ object ShredModelEntry {
 
     implicit val compressionEncodingShow: Show[CompressionEncoding] = Show.show {
       case RawEncoding => s"ENCODE RAW"
-      case Text255Encoding => s"ENCODE TEXT255"
       case ZstdEncoding => s"ENCODE ZSTD"
       case RunLengthEncoding => "ENCODE RUNLENGTH"
     }
@@ -178,8 +175,6 @@ object ShredModelEntry {
 
     case object RunLengthEncoding extends CompressionEncoding
 
-    case object Text255Encoding extends CompressionEncoding
-
     case object ZstdEncoding extends CompressionEncoding
   }
 

modules/core/src/test/scala/com/snowplowanalytics/iglu/schemaddl/redshift/internal/ShredModelEntrySpec.scala

@@ -85,9 +85,9 @@ class ShredModelEntrySpec extends Specification {
   }
 
   "suggest compression" should {
-    "suggest Text255Encoding for enums less then 255 in length" in {
+    "suggest zstd for enums less then 255 in length" in {
       val props = json"""{"type": "string", "enum": ["one", "two"], "maxLength": 42}""".schema
-      ShredModelEntry(dummyPtr, props).compressionEncoding must beEqualTo(Text255Encoding)
+      ShredModelEntry(dummyPtr, props).compressionEncoding must beEqualTo(ZstdEncoding)
     }
 
     "suggest RunLengthEncoding for booleans" in {