fixing a copy-paste error in docs, and in value

Author: mieslep

src/main/java/datastax/astra/migrate/CqlHelper.java

@@ -196,7 +196,7 @@ private String cqlTargetSelectOriginByPK() {
             }
         }
 
-        return "SELECT " + propertyHelper.getAsString(KnownProperties.ORIGIN_COLUMN_NAMES) + " FROM " + getTargetKeyspaceTable() + " WHERE " + keyBinds;
+        return "SELECT " + propertyHelper.getAsString(KnownProperties.TARGET_COLUMN_NAMES) + " FROM " + getTargetKeyspaceTable() + " WHERE " + keyBinds;
     }
 
     public long getLargestWriteTimeStamp(Row row) {

src/main/java/datastax/astra/migrate/properties/PropertyHelper.java

@@ -244,7 +244,7 @@ protected void loadSparkConf() {
             setProperty(KnownProperties.TARGET_COLUMN_NAMES, get(KnownProperties.ORIGIN_COLUMN_NAMES));
         }
 
-        // Target column list defaults to the source column list
+        // Target column key list defaults to the first N columns of the source column list, where N is the size of the target primary key list
         if (null == get(KnownProperties.TARGET_PRIMARY_KEY_TYPES) || getAsString(KnownProperties.TARGET_PRIMARY_KEY_TYPES).isEmpty()) {
             if (null != getMigrationTypeList(KnownProperties.ORIGIN_COLUMN_TYPES) && !getMigrationTypeList(KnownProperties.ORIGIN_COLUMN_TYPES).isEmpty()) {
                 List<MigrateDataType> targetPKTypes = getMigrationTypeList(KnownProperties.ORIGIN_COLUMN_TYPES).subList(0, getStringList(KnownProperties.TARGET_PRIMARY_KEY).size());