[feat](profile) Print changed session var in profile #41016 (#41317)

cherry pick from #41016

fe/fe-core/src/main/java/org/apache/doris/common/profile/Profile.java

@@ -59,8 +59,8 @@ public class Profile {
     private List<ExecutionProfile> executionProfiles = Lists.newArrayList();
     private boolean isFinished;
     private Map<Integer, String> planNodeMap;
-
     private int profileLevel = 3;
+    private String changedSessionVarCache = "";
 
     public Profile(String name, boolean isEnable, int profileLevel, boolean isPipelineX) {
         this.name = name;
@@ -122,6 +122,7 @@ public class Profile {
         // add summary to builder
         summaryProfile.prettyPrint(builder);
         waitProfileCompleteIfNeeded();
+        getChangedSessionVars(builder);
         // Only generate merged profile for select, insert into select.
         // Not support broker load now.
         if (this.profileLevel == MergedProfileLevel && this.executionProfiles.size() == 1) {
@@ -186,4 +187,18 @@ public class Profile {
         Gson gson = new GsonBuilder().setPrettyPrinting().create();
         return gson.toJson(rootProfile.toBrief());
     }
+
+    public void setChangedSessionVar(String changedSessionVar) {
+        this.changedSessionVarCache = changedSessionVar;
+    }
+
+    private void getChangedSessionVars(StringBuilder builder) {
+        if (builder == null) {
+            builder = new StringBuilder();
+        }
+
+        builder.append("\nChanged Session Variables:\n");
+        builder.append(changedSessionVarCache);
+        builder.append("\n");
+    }
 }

fe/fe-core/src/main/java/org/apache/doris/common/util/DebugUtil.java

@@ -26,6 +26,7 @@ import com.google.common.base.Strings;
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.text.DecimalFormat;
+import java.util.List;
 import java.util.UUID;
 
 public class DebugUtil {
@@ -177,4 +178,62 @@ public class DebugUtil {
         e.printStackTrace(new PrintWriter(sw));
         return sw.toString();
     }
+
+    public static String prettyPrintChangedSessionVar(List<List<String>> nestedList) {
+        if (nestedList == null || nestedList.isEmpty()) {
+            return "";
+        }
+
+        StringBuilder output = new StringBuilder();
+
+        // Assuming each inner list has exactly 3 columns
+        int[] columnWidths = new int[3];
+
+        // Calculate the maximum width of each column
+        // First consider the header widths: "VarName", "CurrentValue", "DefaultValue"
+        String[] headers = {"VarName", "CurrentValue", "DefaultValue"};
+        for (int i = 0; i < headers.length; i++) {
+            columnWidths[i] = headers[i].length();  // Initialize with header length
+        }
+
+        // Update column widths based on data
+        for (List<String> row : nestedList) {
+            for (int i = 0; i < row.size(); i++) {
+                columnWidths[i] = Math.max(columnWidths[i], row.get(i).length());
+            }
+        }
+
+        // Build the table header
+        for (int i = 0; i < headers.length; i++) {
+            output.append(String.format("%-" + columnWidths[i] + "s", headers[i]));
+            if (i < headers.length - 1) {
+                output.append(" | ");  // Separator between columns
+            }
+        }
+        output.append("\n");  // Newline after the header
+
+        // Add a separator line for better readability (optional)
+        for (int i = 0; i < headers.length; i++) {
+            output.append(String.format("%-" + columnWidths[i] + "s", Strings.repeat("-", columnWidths[i])));
+            if (i < headers.length - 1) {
+                output.append("-|-");  // Separator between columns
+            }
+        }
+        output.append("\n");  // Newline after the separator
+
+        // Build the table body with proper alignment based on column widths
+        for (List<String> row : nestedList) {
+            for (int i = 0; i < row.size(); i++) {
+                String element = row.get(i);
+                // Pad with spaces if the element is shorter than the column width
+                output.append(String.format("%-" + columnWidths[i] + "s", element));
+                if (i < row.size() - 1) {
+                    output.append(" | ");  // Separator between columns
+                }
+            }
+            output.append("\n");  // Newline after each row
+        }
+
+        return output.toString();
+    }
 }

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

@@ -648,6 +648,8 @@ public class StmtExecutor {
         context.setQueryId(queryId);
         context.setStartTime();
         profile.getSummaryProfile().setQueryBeginTime();
+        List<List<String>> changedSessionVar = VariableMgr.dumpChangedVars(context.getSessionVariable());
+        profile.setChangedSessionVar(DebugUtil.prettyPrintChangedSessionVar(changedSessionVar));
         context.setStmtId(STMT_ID_GENERATOR.incrementAndGet());
 
         parseByNereids();

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

@@ -795,6 +795,42 @@ public class VariableMgr {
         return changedRows;
     }
 
+    public static List<List<String>> dumpChangedVars(SessionVariable sessionVar) {
+        // Hold the read lock when session dump, because this option need to access global variable.
+        rlock.lock();
+        List<List<String>> changedRows = Lists.newArrayList();
+        try {
+            for (Map.Entry<String, VarContext> entry : ctxByDisplayVarName.entrySet()) {
+                VarContext ctx = entry.getValue();
+                List<String> row = Lists.newArrayList();
+                String varName = entry.getKey();
+                String curValue = getValue(sessionVar, ctx.getField());
+                String defaultValue = ctx.getDefaultValue();
+                if (VariableVarConverters.hasConverter(varName)) {
+                    try {
+                        defaultValue = VariableVarConverters.decode(varName, Long.valueOf(defaultValue));
+                        curValue = VariableVarConverters.decode(varName, Long.valueOf(curValue));
+                    } catch (DdlException e) {
+                        LOG.warn("Decode session variable {} failed, reason: {}", varName, e.getMessage());
+                    }
+                }
+
+                if (curValue.equals(defaultValue)) {
+                    continue;
+                }
+
+                row.add(varName);
+                row.add(curValue);
+                row.add(defaultValue);
+                changedRows.add(row);
+            }
+        } finally {
+            rlock.unlock();
+        }
+
+        return changedRows;
+    }
+
     @Retention(RetentionPolicy.RUNTIME)
     public @interface VarAttr {
         // Name in show variables and set statement;