update

Author: Gabriel39

be/src/pipeline/exec/file_scan_operator.cpp

@@ -34,9 +34,11 @@ namespace doris::pipeline {
 
 int FileScanLocalState::max_scanners_concurrency(RuntimeState* state) {
     /*
-     * The max concurrency of file scanners is determined by:
+     * The max concurrency of file scanners for each FileScanLocalState is determined by:
      * 1. User specified max_file_scanners_concurrency which is set through session variable.
-     * 2. The max threads of remote scan scheduler.
+     * 2. Default: std::max((std::max(512, CpuInfo::num_cores() * 10)), config::doris_scanner_thread_pool_thread_num) * 2 / operator parallelism
+     *
+     * If this is a serial operator, the max concurrency should multiply by the number of parallel instances of the operator.
      */
     return (state->max_file_scanners_concurrency()
                     ? state->max_file_scanners_concurrency()

be/src/pipeline/exec/scan_operator.cpp

@@ -73,6 +73,13 @@ bool ScanLocalState<Derived>::should_run_serial() const {
 }
 
 int ScanLocalStateBase::max_scanners_concurrency(RuntimeState* state) {
+    /*
+     * The max concurrency of scanners for each ScanLocalStateBase is determined by:
+     * 1. User specified max_scanners_concurrency which is set through session variable.
+     * 2. Default: config::doris_scanner_thread_pool_thread_num / operator parallelism
+     *
+     * If this is a serial operator, the max concurrency should multiply by the number of parallel instances of the operator.
+     */
     return (state->max_scanners_concurrency()
                     ? state->max_scanners_concurrency()
                     : _state->get_query_ctx()->get_scan_scheduler()->get_max_threads() * 2 /

fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java

@@ -981,12 +981,12 @@ public static double getHotValueThreshold() {
             "The max threads to read data of ScanNode, "
                     + "default 0, use doris_scanner_thread_pool_thread_num in be.conf"
     })
-    public int maxScannersConcurrency = 4;
+    public int maxScannersConcurrency = 0;
 
     @VariableMgr.VarAttr(name = MAX_FILE_SCANNERS_CONCURRENCY, needForward = true, description = {
             "FileScanNode 扫描数据的最大并发",
             "The max threads to read data of FileScanNode"})
-    public int maxFileScannersConcurrency = 16;
+    public int maxFileScannersConcurrency = 0;
 
     @VariableMgr.VarAttr(name = LOCAL_EXCHANGE_FREE_BLOCKS_LIMIT)
     public int localExchangeFreeBlocksLimit = 4;