improve desc

Author: wForget

common/src/main/scala/org/apache/comet/CometConf.scala

@@ -654,7 +654,7 @@ object CometConf extends ShimCometConf {
     conf(s"spark.hadoop.$COMET_LIBHDFS_SCHEMES_KEY")
       .doc(
         "Defines filesystem schemes (e.g., hdfs, webhdfs) that the native side accesses " +
-          "via libhdfs, separated by commas.")
+          "via libhdfs, separated by commas. Valid only when built with hdfs feature enabled.")
       .stringConf
       .createOptional
 

docs/source/user-guide/compatibility.md

@@ -75,7 +75,7 @@ The `native_datafusion` scan has some additional limitations:
 
 ### S3 Support with `native_iceberg_compat`
 
-- When using the default AWS S3 endpoint (no custom endpoint configured), a valid region is required. Comet 
+- When using the default AWS S3 endpoint (no custom endpoint configured), a valid region is required. Comet
   will attempt to resolve the region if it is not provided.
 
 ## ANSI Mode

docs/source/user-guide/configs.md

@@ -91,5 +91,5 @@ Comet provides the following configuration settings.
 | spark.comet.shuffle.preferDictionary.ratio | The ratio of total values to distinct values in a string column to decide whether to prefer dictionary encoding when shuffling the column. If the ratio is higher than this config, dictionary encoding will be used on shuffling string column. This config is effective if it is higher than 1.0. Note that this config is only used when `spark.comet.exec.shuffle.mode` is `jvm`. | 10.0 |
 | spark.comet.shuffle.sizeInBytesMultiplier | Comet reports smaller sizes for shuffle due to using Arrow's columnar memory format and this can result in Spark choosing a different join strategy due to the estimated size of the exchange being smaller. Comet will multiple sizeInBytes by this amount to avoid regressions in join strategy. | 1.0 |
 | spark.comet.sparkToColumnar.supportedOperatorList | A comma-separated list of operators that will be converted to Arrow columnar format when 'spark.comet.sparkToColumnar.enabled' is true | Range,InMemoryTableScan |
-| spark.hadoop.fs.comet.libhdfs.schemes | Defines filesystem schemes (e.g., hdfs, webhdfs) that the native side accesses via libhdfs, separated by commas. | |
+| spark.hadoop.fs.comet.libhdfs.schemes | Defines filesystem schemes (e.g., hdfs, webhdfs) that the native side accesses via libhdfs, separated by commas. Valid only when built with hdfs feature enabled. | |
 <!--END:CONFIG_TABLE-->