[fix](routineload) Persist the current load definition

fe/fe-catalog/src/main/java/org/apache/doris/analysis/AGENTS.md

@@ -0,0 +1,26 @@
+# Legacy Expr persistence — Review Guide
+
+Legacy `Expr` objects are persisted by metadata consumers such as Routine Load images and
+`ALTER ROUTINE LOAD` journals. Doris Gson serializes only fields annotated with
+`@SerializedName`, so an unclassified field can be silently lost during FE recovery.
+
+## Expr changes
+
+- [ ] Any field that changes `ExprToSqlVisitor` output has a stable `@SerializedName` key.
+- [ ] Existing serialized keys are not renamed, removed, or reused for a different meaning.
+- [ ] Analysis caches and execution-only fields remain unpersisted only when they can be rebuilt
+      after the restored expression is converted to SQL and analyzed again.
+- [ ] Every unpersisted instance field is listed with that rationale in
+      `ExprGsonSerializationTest.NON_DURABLE_EXPR_FIELDS`; do not add fields to the list merely to
+      make the test pass.
+- [ ] New concrete `Expr` subtypes are registered in both Gson factories and have a non-default
+      sample in `ExprGsonSerializationTest`.
+- [ ] Samples set every SQL-relevant option to a non-default value so semantic loss is observable.
+
+## Required tests
+
+- [ ] `ExprGsonSerializationTest` preserves the concrete subtype and `ExprToSqlVisitor` output
+      with and without table names across Gson round-trip.
+- [ ] Metadata consumers that introduce a new Expr carrier add an image and journal replay test.
+- [ ] Routine Load expression changes cover column mappings, preceding filters, where filters, and
+      delete conditions as applicable.

fe/fe-catalog/src/main/java/org/apache/doris/analysis/FunctionCallExpr.java

@@ -43,6 +43,7 @@ public class FunctionCallExpr extends Expr {
 
     private FunctionParams aggFnParams;
 
+    @SerializedName("obe")
     private List<OrderByElement> orderByElements = Lists.newArrayList();
 
     // check analytic function

fe/fe-catalog/src/main/java/org/apache/doris/analysis/MatchPredicate.java

@@ -72,6 +72,7 @@ public String getName() {
     private String invertedIndexParserStopwords = "";
     private String invertedIndexAnalyzerName = "";
     // Fields for SQL generation
+    @SerializedName("ea")
     private String explicitAnalyzer = "";
 
     private MatchPredicate() {

fe/fe-catalog/src/main/java/org/apache/doris/analysis/OrderByElement.java

@@ -21,18 +21,22 @@
 package org.apache.doris.analysis;
 
 import com.google.common.collect.Lists;
+import com.google.gson.annotations.SerializedName;
 
 import java.util.List;
 
 /**
  * Combination of expr and ASC/DESC, and nulls ordering.
  */
 public class OrderByElement {
+    @SerializedName("e")
     private Expr expr;
+    @SerializedName("ia")
     private final boolean isAsc;
 
     // Represents the NULLs ordering specified: true when "NULLS FIRST", false when
     // "NULLS LAST", and null if not specified.
+    @SerializedName("nfp")
     private final Boolean nullsFirstParam;
 
     public OrderByElement(Expr expr, boolean isAsc, Boolean nullsFirstParam) {

fe/fe-catalog/src/main/java/org/apache/doris/analysis/PlaceHolderExpr.java

@@ -22,12 +22,15 @@
 import org.apache.doris.catalog.Type;
 
 import com.google.common.base.Preconditions;
+import com.google.gson.annotations.SerializedName;
 
 import java.nio.ByteBuffer;
 
 // PlaceHolderExpr is a reference class point to real LiteralExpr
 public class PlaceHolderExpr extends LiteralExpr {
+    @SerializedName("le")
     private LiteralExpr lExpr;
+    @SerializedName("mtc")
     int mysqlTypeCode = -1;
 
     public PlaceHolderExpr() {

fe/fe-catalog/src/main/java/org/apache/doris/analysis/SearchPredicate.java

@@ -21,6 +21,8 @@
 import org.apache.doris.catalog.Index;
 import org.apache.doris.catalog.Type;
 
+import com.google.gson.annotations.SerializedName;
+
 import java.util.Collections;
 import java.util.List;
 
@@ -29,6 +31,7 @@
  * for BE VSearchExpr processing. This is only used during FE->BE translation.
  */
 public class SearchPredicate extends Predicate {
+    @SerializedName("dsl")
     private final String dslString;
     private final QsPlan qsPlan;
     private final List<Index> fieldIndexes;

fe/fe-catalog/src/main/java/org/apache/doris/analysis/SlotRef.java

@@ -38,7 +38,9 @@ public class SlotRef extends Expr {
     @SerializedName("col")
     private String col;
     // Used in toSql
+    @SerializedName("l")
     private String label;
+    @SerializedName("scp")
     private List<String> subColPath;
 
     // results of analysis

fe/fe-catalog/src/main/java/org/apache/doris/analysis/TimeV2Literal.java

@@ -20,14 +20,21 @@
 import org.apache.doris.catalog.ScalarType;
 import org.apache.doris.catalog.Type;
 
+import com.google.gson.annotations.SerializedName;
+
 public class TimeV2Literal extends LiteralExpr {
     public static final TimeV2Literal MIN_VALUE = new TimeV2Literal(838, 59, 59, 999999, 6, true);
     public static final TimeV2Literal MAX_VALUE = new TimeV2Literal(838, 59, 59, 999999, 6, false);
 
+    @SerializedName("h")
     protected int hour;
+    @SerializedName("m")
     protected int minute;
+    @SerializedName("s")
     protected int second;
+    @SerializedName("us")
     protected int microsecond;
+    @SerializedName("neg")
     protected boolean negative;
 
     /**

fe/fe-catalog/src/main/java/org/apache/doris/analysis/VariableExpr.java

@@ -17,13 +17,17 @@
 
 package org.apache.doris.analysis;
 
+import com.google.gson.annotations.SerializedName;
+
 import java.math.BigDecimal;
 import java.util.Objects;
 
 // Variable expr: including the system variable and user define variable.
 // Converted to StringLiteral in analyze, if this variable is not exist, throw AnalysisException.
 public class VariableExpr extends Expr {
+    @SerializedName("n")
     private String name;
+    @SerializedName("st")
     private SetType setType;
     private boolean isNull;
     private boolean boolValue;

fe/fe-core/src/main/java/org/apache/doris/analysis/Separator.java

@@ -20,13 +20,16 @@
 import org.apache.doris.common.AnalysisException;
 
 import com.google.common.base.Strings;
+import com.google.gson.annotations.SerializedName;
 
 import java.io.StringWriter;
 
 public class Separator {
     private static final String HEX_STRING = "0123456789ABCDEF";
 
+    @SerializedName("os")
     private final String oriSeparator;
+    @SerializedName("s")
     private String separator;
 
     public Separator(String separator) {

fe/fe-core/src/main/java/org/apache/doris/load/RoutineLoadDesc.java

@@ -26,19 +26,29 @@
 import org.apache.doris.load.loadv2.LoadTask;
 
 import com.google.common.base.Strings;
+import com.google.gson.annotations.SerializedName;
 
 import java.util.List;
 
 public class RoutineLoadDesc {
+    @SerializedName("cs")
     private final Separator columnSeparator;
+    @SerializedName("ld")
     private final Separator lineDelimiter;
+    @SerializedName("cols")
     private final List<ImportColumnDesc> columnsInfo;
+    @SerializedName("pf")
     private final Expr precedingFilter;
+    @SerializedName("f")
     private final Expr filter;
+    @SerializedName("dc")
     private final Expr deleteCondition;
+    @SerializedName("mt")
     private LoadTask.MergeType mergeType;
     // nullable
+    @SerializedName("pn")
     private final PartitionNamesInfo partitionNamesInfo;
+    @SerializedName("sc")
     private final String sequenceColName;
 
     public RoutineLoadDesc(Separator columnSeparator, Separator lineDelimiter, List<ImportColumnDesc> columnsInfo,