[fix](prepared statement)Fix prepareCommand couldn't get fields metadata bug. (#49206)

### What problem does this PR solve?

Fix prepareCommand couldn't get fields metadata bug. In the prepare
stage, Doris should return the output column info to the client, this is
required by mysql api definition.

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

### Release note

None

### Check List (For Author)

- Test <!-- At least one of them must be included. -->
    - [ ] Regression test
    - [ ] Unit Test
    - [ ] Manual test (add detailed scripts or steps below)
    - [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
        - [ ] Previous test can cover this change.
        - [ ] No code files have been changed.
        - [ ] Other reason <!-- Add your reason?  -->

- Behavior changed:
    - [ ] No.
    - [ ] Yes. <!-- Explain the behavior change -->

- Does this need documentation?
    - [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
apache/doris-website#1214 -->

### Check List (For Reviewer who merge this PR)

- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
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should merge into -->

Author: Jibing-Li

fe/fe-core/src/main/java/org/apache/doris/nereids/StatementContext.java

@@ -214,6 +214,8 @@ public enum TableFrom {
 
     private boolean privChecked;
 
+    private boolean prepareStage = false;
+
     public StatementContext() {
         this(ConnectContext.get(), null, 0);
     }
@@ -774,4 +776,12 @@ public boolean isPrivChecked() {
     public void setPrivChecked(boolean privChecked) {
         this.privChecked = privChecked;
     }
+
+    public void setPrepareStage(boolean isPrepare) {
+        this.prepareStage = isPrepare;
+    }
+
+    public boolean isPrepareStage() {
+        return prepareStage;
+    }
 }

fe/fe-core/src/main/java/org/apache/doris/nereids/rules/analysis/ExpressionAnalyzer.java

@@ -623,6 +623,11 @@ public Expression visitPlaceholder(Placeholder placeholder, ExpressionRewriteCon
         }
         Expression realExpr = context.cascadesContext.getStatementContext()
                     .getIdToPlaceholderRealExpr().get(placeholder.getPlaceholderId());
+        // In prepare stage, the realExpr has not been set, set it to NullLiteral so that we can plan the statement
+        // and get the output slots in prepare stage, which is required by Mysql api definition.
+        if (realExpr == null && context.cascadesContext.getStatementContext().isPrepareStage()) {
+            realExpr = new NullLiteral();
+        }
         return visit(realExpr, context);
     }
 

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/Command.java

@@ -28,10 +28,13 @@
 import org.apache.doris.nereids.trees.plans.Plan;
 import org.apache.doris.nereids.trees.plans.PlanType;
 import org.apache.doris.nereids.trees.plans.logical.LogicalPlan;
+import org.apache.doris.qe.CommonResultSet.CommonResultSetMetaData;
 import org.apache.doris.qe.ConnectContext;
+import org.apache.doris.qe.ResultSetMetaData;
 import org.apache.doris.qe.StmtExecutor;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
 
 import java.util.List;
 import java.util.Optional;
@@ -130,4 +133,10 @@ public void verifyCommandSupported(ConnectContext ctx) throws DdlException {
     // see checkStmtSupported() in fe/fe-core/src/main/java/org/apache/doris/qe/ShowExecutor.java
     // override this method if the command is not supported in cloud mode
     protected void checkSupportedInCloudMode(ConnectContext ctx) throws DdlException {}
+
+    // For prepare statement only, used to get the result set metadata in prepare stage.
+    // Subclass need to override this to return correct metadata.
+    public ResultSetMetaData getResultSetMetaData() {
+        return new CommonResultSetMetaData(Lists.newArrayList());
+    }
 }

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/ExecuteCommand.java

@@ -65,6 +65,8 @@ public <R, C> R accept(PlanVisitor<R, C> visitor, C context) {
 
     @Override
     public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
+        StatementContext statementContext = ctx.getStatementContext();
+        statementContext.setPrepareStage(false);
         PreparedStatementContext preparedStmtCtx = ctx.getPreparedStementContext(stmtName);
         if (null == preparedStmtCtx) {
             throw new AnalysisException(

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/HelpCommand.java

@@ -125,6 +125,11 @@ public ShowResultSet doRun(ConnectContext ctx, StmtExecutor executor) throws Exc
         return resultSet;
     }
 
+    @Override
+    public ShowResultSetMetaData getMetaData() {
+        return ShowResultSetMetaData.builder().build();
+    }
+
     @Override
     public <R, C> R accept(PlanVisitor<R, C> visitor, C context) {
         return visitor.visitHelpCommand(this, context);

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/PrepareCommand.java

@@ -18,17 +18,24 @@
 package org.apache.doris.nereids.trees.plans.commands;
 
 import org.apache.doris.analysis.StmtType;
+import org.apache.doris.catalog.Column;
 import org.apache.doris.mysql.MysqlCommand;
+import org.apache.doris.nereids.StatementContext;
 import org.apache.doris.nereids.trees.expressions.Placeholder;
+import org.apache.doris.nereids.trees.expressions.Slot;
+import org.apache.doris.nereids.trees.expressions.SlotReference;
 import org.apache.doris.nereids.trees.plans.PlanType;
 import org.apache.doris.nereids.trees.plans.commands.insert.InsertIntoTableCommand;
 import org.apache.doris.nereids.trees.plans.logical.LogicalPlan;
 import org.apache.doris.nereids.trees.plans.visitor.PlanVisitor;
+import org.apache.doris.nereids.types.DataType;
 import org.apache.doris.qe.ConnectContext;
 import org.apache.doris.qe.OriginStatement;
 import org.apache.doris.qe.PreparedStatementContext;
+import org.apache.doris.qe.ResultSetMetaData;
 import org.apache.doris.qe.StmtExecutor;
 
+import com.google.common.collect.Lists;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
@@ -99,6 +106,18 @@ public List<String> getLabels() {
     @Override
     public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
         List<String> labels = getLabels();
+        StatementContext statementContext = ctx.getStatementContext();
+        statementContext.setPrepareStage(true);
+        List<Slot> slots;
+        if (logicalPlan instanceof Command) {
+            ResultSetMetaData md = ((Command) logicalPlan).getResultSetMetaData();
+            slots = Lists.newArrayList();
+            for (Column c : md.getColumns()) {
+                slots.add(new SlotReference(c.getName(), DataType.fromCatalogType(c.getType())));
+            }
+        } else {
+            slots = executor.planPrepareStatementSlots();
+        }
         // register prepareStmt
         if (LOG.isDebugEnabled()) {
             LOG.debug("add prepared statement {}, isBinaryProtocol {}",
@@ -111,7 +130,7 @@ public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
         ctx.addPreparedStatementContext(name,
                 new PreparedStatementContext(this, ctx, ctx.getStatementContext(), name));
         if (ctx.getCommand() == MysqlCommand.COM_STMT_PREPARE && !ctx.isProxy()) {
-            executor.sendStmtPrepareOK(Integer.parseInt(name), labels);
+            executor.sendStmtPrepareOK(Integer.parseInt(name), labels, slots);
         }
     }
 

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/ShowAnalyzeCommand.java

@@ -206,7 +206,12 @@ private ShowResultSet handleShowAnalyze() {
                         analysisInfo.catalogId, analysisInfo.dbId, analysisInfo.tblId, e.getMessage());
             }
         }
-        return new ShowResultSet(META_DATA, resultRows);
+        return new ShowResultSet(getMetaData(), resultRows);
+    }
+
+    @Override
+    public ShowResultSetMetaData getMetaData() {
+        return META_DATA;
     }
 
     @Override

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/ShowAuthorsCommand.java

@@ -50,9 +50,14 @@ public <R, C> R accept(PlanVisitor<R, C> visitor, C context) {
         return visitor.visitShowAuthorsCommand(this, context);
     }
 
+    @Override
+    public ShowResultSetMetaData getMetaData() {
+        return META_DATA;
+    }
+
     @Override
     public ShowResultSet doRun(ConnectContext ctx, StmtExecutor executor) throws Exception {
         List<List<String>> rowSet = Lists.newArrayList();
-        return new ShowResultSet(META_DATA, rowSet);
+        return new ShowResultSet(getMetaData(), rowSet);
     }
 }

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/ShowBackupCommand.java

@@ -79,7 +79,7 @@ public ShowBackupCommand(String dbName, Expression where) {
     /**
      * get metadata
      */
-    private ShowResultSetMetaData getMetaData() {
+    public ShowResultSetMetaData getMetaData() {
         ShowResultSetMetaData.Builder builder = ShowResultSetMetaData.builder();
         for (String title : TITLE_NAMES) {
             builder.addColumn(new Column(title, ScalarType.STRING));

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/ShowCharsetCommand.java

@@ -46,6 +46,11 @@ public ShowCharsetCommand() {
         super(PlanType.SHOW_CHARSET_COMMAND);
     }
 
+    @Override
+    public ShowResultSetMetaData getMetaData() {
+        return CHARSET_META_DATA;
+    }
+
     @Override
     public ShowResultSet doRun(ConnectContext ctx, StmtExecutor executor) throws Exception {
         List<List<String>> rows = Lists.newArrayList();
@@ -57,7 +62,7 @@ public ShowResultSet doRun(ConnectContext ctx, StmtExecutor executor) throws Exc
         row.add("4");
         rows.add(row);
 
-        return new ShowResultSet(CHARSET_META_DATA, rows);
+        return new ShowResultSet(getMetaData(), rows);
     }
 
     @Override