Merge pull request #53709 from ClickHouse/reasonable-prefetches-by-de…

…fault

Reasonable prefetches for remote FS by default

src/Core/Settings.h

@@ -712,15 +712,15 @@ class IColumn;
     \
     M(Bool, load_marks_asynchronously, false, "Load MergeTree marks asynchronously", 0) \
     M(Bool, enable_filesystem_read_prefetches_log, false, "Log to system.filesystem prefetch_log during query. Should be used only for testing or debugging, not recommended to be turned on by default", 0) \
-    M(Bool, allow_prefetched_read_pool_for_remote_filesystem, false, "Prefer prefethed threadpool if all parts are on remote filesystem", 0) \
+    M(Bool, allow_prefetched_read_pool_for_remote_filesystem, true, "Prefer prefethed threadpool if all parts are on remote filesystem", 0) \
     M(Bool, allow_prefetched_read_pool_for_local_filesystem, false, "Prefer prefethed threadpool if all parts are on remote filesystem", 0) \
     \
     M(UInt64, prefetch_buffer_size, DBMS_DEFAULT_BUFFER_SIZE, "The maximum size of the prefetch buffer to read from the filesystem.", 0) \
     M(UInt64, filesystem_prefetch_step_bytes, 0, "Prefetch step in bytes. Zero means `auto` - approximately the best prefetch step will be auto deduced, but might not be 100% the best. The actual value might be different because of setting filesystem_prefetch_min_bytes_for_single_read_task", 0) \
     M(UInt64, filesystem_prefetch_step_marks, 0, "Prefetch step in marks. Zero means `auto` - approximately the best prefetch step will be auto deduced, but might not be 100% the best. The actual value might be different because of setting filesystem_prefetch_min_bytes_for_single_read_task", 0) \
     M(UInt64, filesystem_prefetch_min_bytes_for_single_read_task, "8Mi", "Do not parallelize within one file read less than this amount of bytes. E.g. one reader will not receive a read task of size less than this amount. This setting is recommended to avoid spikes of time for aws getObject requests to aws", 0) \
-    M(UInt64, filesystem_prefetch_max_memory_usage, "1Gi", "Maximum memory usage for prefetches", 0) \
-    M(UInt64, filesystem_prefetches_limit, 0, "Maximum number of prefetches. Zero means unlimited. A setting `filesystem_prefetches_max_memory_usage` is more recommended if you want to limit the number of prefetches", 0) \
+    M(UInt64, filesystem_prefetch_max_memory_usage, "1Gi", "Maximum memory usage for prefetches.", 0) \
+    M(UInt64, filesystem_prefetches_limit, 200, "Maximum number of prefetches. Zero means unlimited. A setting `filesystem_prefetches_max_memory_usage` is more recommended if you want to limit the number of prefetches", 0) \
     \
     M(UInt64, use_structure_from_insertion_table_in_table_functions, 2, "Use structure from insertion table instead of schema inference from data. Possible values: 0 - disabled, 1 - enabled, 2 - auto", 0) \
     \