[Fix](Nereids) fix append_trailing_char_if_absent function return null (#40820)

fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/FoldConstantRuleOnBE.java

@@ -72,7 +72,10 @@ public class FoldConstantRuleOnBE extends AbstractExpressionRewriteRule {
 
     @Override
     public Expression rewrite(Expression expr, ExpressionRewriteContext ctx) {
-        Expression expression = FoldConstantRuleOnFE.INSTANCE.rewrite(expr, ctx);
+        if(ctx.cascadesContext.getConnectContext().getSessionVariable().isDebugSkipFoldConstant()) {
+		    return null;
+		}
+	    Expression expression = FoldConstantRuleOnFE.INSTANCE.rewrite(expr, ctx);
         return foldByBE(expression, ctx);
     }
 

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/executable/ExecutableFunctions.java

@@ -26,7 +26,9 @@
 import org.apache.doris.nereids.trees.expressions.literal.FloatLiteral;
 import org.apache.doris.nereids.trees.expressions.literal.IntegerLiteral;
 import org.apache.doris.nereids.trees.expressions.literal.LargeIntLiteral;
+import org.apache.doris.nereids.trees.expressions.literal.NullLiteral;
 import org.apache.doris.nereids.trees.expressions.literal.SmallIntLiteral;
+import org.apache.doris.nereids.trees.expressions.literal.StringLikeLiteral;
 import org.apache.doris.nereids.trees.expressions.literal.TinyIntLiteral;
 import org.apache.doris.nereids.trees.expressions.literal.VarcharLiteral;
 
@@ -91,13 +93,19 @@ public static Expression acos(DoubleLiteral literal) {
         return new DoubleLiteral(Math.acos(literal.getValue()));
     }
 
-    @ExecFunction(name = "append_trailing_if_char_absent", argTypes = {"VARCHAR", "VARCHAR"}, returnType = "VARCHAR")
-    public static Expression appendTrailingIfCharAbsent(VarcharLiteral literal, VarcharLiteral chr) {
-        if (literal.getValue().length() != 1) {
-            return null;
+    /**
+     * append_trailing_char_if_absent function
+     */
+    @ExecFunction(name = "append_trailing_char_if_absent", argTypes = {"VARCHAR", "VARCHAR"}, returnType = "VARCHAR")
+    public static Expression appendTrailingIfCharAbsent(StringLikeLiteral literal, StringLikeLiteral chr) {
+        if (chr.getStringValue().length() != 1) {
+            return new NullLiteral(literal.getDataType());
+        }
+        if (literal.getStringValue().endsWith(chr.getStringValue())) {
+            return literal;
+        } else {
+            return new VarcharLiteral(literal.getStringValue() + chr.getStringValue());
         }
-        return literal.getValue().endsWith(chr.getValue()) ? literal
-                : new VarcharLiteral(literal.getValue() + chr.getValue());
     }
 
     @ExecFunction(name = "e", argTypes = {}, returnType = "DOUBLE")

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

@@ -121,6 +121,8 @@ public class SessionVariable implements Serializable, Writable {
     public static final String PREFER_JOIN_METHOD = "prefer_join_method";
 
     public static final String ENABLE_FOLD_CONSTANT_BY_BE = "enable_fold_constant_by_be";
+    public static final String DEBUG_SKIP_FOLD_CONSTANT = "debug_skip_fold_constant";
+
     public static final String ENABLE_ODBC_TRANSCATION = "enable_odbc_transcation";
     public static final String ENABLE_SQL_CACHE = "enable_sql_cache";
     public static final String ENABLE_PARTITION_CACHE = "enable_partition_cache";
@@ -807,6 +809,9 @@ public class SessionVariable implements Serializable, Writable {
     @VariableMgr.VarAttr(name = ENABLE_FOLD_CONSTANT_BY_BE, fuzzy = true)
     private boolean enableFoldConstantByBe = false;
 
+    @VariableMgr.VarAttr(name = DEBUG_SKIP_FOLD_CONSTANT)
+    public boolean debugSkipFoldConstant = false;
+
     @VariableMgr.VarAttr(name = RUNTIME_FILTER_MODE, needForward = true)
     private String runtimeFilterMode = "GLOBAL";
 
@@ -1933,6 +1938,10 @@ public boolean isEnableFoldConstantByBe() {
         return enableFoldConstantByBe;
     }
 
+    public boolean isDebugSkipFoldConstant() {
+        return debugSkipFoldConstant;
+    }
+
     public boolean isEnableNereidsDML() {
         return enableNereidsDML;
     }
@@ -1941,6 +1950,10 @@ public void setEnableFoldConstantByBe(boolean foldConstantByBe) {
         this.enableFoldConstantByBe = foldConstantByBe;
     }
 
+    public void setDebugSkipFoldConstant(boolean debugSkipFoldConstant) {
+        this.debugSkipFoldConstant = debugSkipFoldConstant;
+    }
+
     public int getParallelExecInstanceNum() {
         ConnectContext connectContext = ConnectContext.get();
         if (connectContext != null && connectContext.getEnv() != null && connectContext.getEnv().getAuth() != null) {

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

@@ -1221,7 +1221,8 @@ private void analyzeAndGenerateQueryPlan(TQueryOptions tQueryOptions) throws Use
         if (parsedStmt instanceof QueryStmt || parsedStmt instanceof InsertStmt) {
             ExprRewriter rewriter = analyzer.getExprRewriter();
             rewriter.reset();
-            if (context.getSessionVariable().isEnableFoldConstantByBe()) {
+            if (context.getSessionVariable().isEnableFoldConstantByBe()
+                    && !context.getSessionVariable().isDebugSkipFoldConstant()) {
                 // fold constant expr
                 parsedStmt.foldConstant(rewriter, tQueryOptions);
 

regression-test/framework/src/main/groovy/org/apache/doris/regression/suite/Suite.groovy

@@ -947,6 +947,20 @@ class Suite implements GroovyInterceptable {
         return debugPoint
     }
 
+    void testFoldConst(String foldSql) {
+        String openFoldConstant = "set debug_skip_fold_constant=false";
+        sql(openFoldConstant)
+        logger.info(foldSql)
+        List<List<Object>> resultByFoldConstant = sql(foldSql)
+        logger.info("result by fold constant: " + resultByFoldConstant.toString())
+        String closeFoldConstant = "set debug_skip_fold_constant=true";
+        sql(closeFoldConstant)
+        logger.info(foldSql)
+        List<List<Object>> resultExpected = sql(foldSql)
+        logger.info("result expected: " + resultExpected.toString())
+        Assert.assertEquals(resultExpected, resultByFoldConstant)
+    }
+
     boolean isCloudMode() {
         return false
     }

regression-test/suites/nereids_p0/expression/fold_constant/fold_constant_by_fe.groovy

@@ -161,4 +161,90 @@ suite("test_fold_constant_by_fe") {
     res = sql """explain select "12" like '%123%'"""
     assertTrue(res.contains("like"))
 
+    // Normal Usage Test Cases
+
+    // Test Case 1: Append missing trailing character
+    testFoldConst("select append_trailing_char_if_absent('hello', '!')")
+    // Expected Output: 'hello!'
+
+    // Test Case 2: Trailing character already present
+    testFoldConst("select append_trailing_char_if_absent('hello!', '!')")
+    // Expected Output: 'hello!'
+
+    // Test Case 3: Append trailing space
+    testFoldConst("select append_trailing_char_if_absent('hello', ' ')")
+    // Expected Output: 'hello '
+
+    // Test Case 4: Empty string input
+    testFoldConst("select append_trailing_char_if_absent('', '!')")
+    // Expected Output: '!'
+
+    // Test Case 5: Append different character
+    testFoldConst("select append_trailing_char_if_absent('hello', '?')")
+    // Expected Output: 'hello?'
+
+    // Test Case 6: String ends with a different character
+    testFoldConst("select append_trailing_char_if_absent('hello?', '!')")
+    // Expected Output: 'hello?!'
+
+    // Edge and Unusual Usage Test Cases
+
+    // Test Case 7: Input is NULL
+    testFoldConst("select append_trailing_char_if_absent(NULL, '!')")
+    // Expected Output: NULL
+
+    // Test Case 8: Trailing character is NULL
+    testFoldConst("select append_trailing_char_if_absent('hello', NULL)")
+    // Expected Output: NULL
+
+    // Test Case 9: Empty trailing character
+    testFoldConst("select append_trailing_char_if_absent('hello', '')")
+    // Expected Output: Error or no change depending on implementation
+
+    // Test Case 10: Trailing character is more than 1 character long
+    testFoldConst("select append_trailing_char_if_absent('hello', 'ab')")
+    // Expected Output: Error
+
+    // Test Case 11: Input string is a number
+    testFoldConst("select append_trailing_char_if_absent(12345, '!')")
+    // Expected Output: Error or '12345!'
+
+    // Test Case 12: Trailing character is a number
+    testFoldConst("select append_trailing_char_if_absent('hello', '1')")
+    // Expected Output: 'hello1'
+
+    // Test Case 13: Input is a single character
+    testFoldConst("select append_trailing_char_if_absent('h', '!')")
+    // Expected Output: 'h!'
+
+    // Test Case 14: Unicode character as input and trailing character
+    testFoldConst("select append_trailing_char_if_absent('こんにちは', '!')")
+    // Expected Output: 'こんにちは!'
+
+    // Test Case 15: Multibyte character as trailing character
+    testFoldConst("select append_trailing_char_if_absent('hello', '😊')")
+    // Expected Output: 'hello😊'
+
+    // Test Case 16: Long string input
+    testFoldConst("select append_trailing_char_if_absent('This is a very long string', '.')")
+    // Expected Output: 'This is a very long string.'
+
+    // Error Handling Test Cases
+
+    // Test Case 17: Invalid trailing character data type (numeric)
+    testFoldConst("select append_trailing_char_if_absent('hello', 1)")
+    // Expected Output: Error
+
+    // Test Case 18: Invalid input data type (integer)
+    testFoldConst("select append_trailing_char_if_absent(12345, '!')")
+    // Expected Output: Error or '12345!'
+
+    // Test Case 19: Non-ASCII characters
+    testFoldConst("select append_trailing_char_if_absent('Привет', '!')")
+    // Expected Output: 'Привет!'
+
+    // Test Case 20: Trailing character with whitespace
+    testFoldConst("select append_trailing_char_if_absent('hello', ' ')")
+    // Expected Output: 'hello '
+
 }