[Enhancement]Add session variable enable_compare_for_null to support compare null …

[even986025158]

…when use =
need use = to compare null = null and want to it return true

Why I'm doing:

Some services migrated from other systems want to use = for null comparison, but do not want to modify the SQL

What I'm doing:

add the session variable enable_compare_for_null to support compare null with =
Fixes #issue

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
• I have added documentation for my new feature or new function
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 3.3
  • 3.2
  • 3.1
  • 3.0
  • 2.5

[starrocks-cr]

The most risky bug in this code is:
Serialization inconsistency due to missing enableCompareForNull field.

You can modify the code like this:

    @@ -173,6 +173,7 @@ public class SessionVariable implements Serializable, Writable, Cloneable {
     public static final String QUERY_CACHE_TYPE = "query_cache_type";
     public static final String INTERACTIVE_TIMEOUT = "interactive_timeout";
     public static final String WAIT_TIMEOUT = "wait_timeout";
+    public static final String ENABLE_COMPARE_FOR_NULL = "enable_compare_for_null";
 
     public static final String CATALOG = "catalog";
     public static final String NET_WRITE_TIMEOUT = "net_write_timeout";
@@ -1005,6 +1006,9 @@ public static MaterializedViewRewriteMode parse(String str) {
     @VariableMgr.VarAttr(name = WAIT_TIMEOUT)
     private int waitTimeout = 28800;
 
+    @VariableMgr.VarAttr(name = ENABLE_COMPARE_FOR_NULL)
+    private boolean enableCompareForNull = false;
+
     // The number of seconds to wait for a block to be written to a connection before aborting the write
     @VariableMgr.VarAttr(name = NET_WRITE_TIMEOUT)
     private int netWriteTimeout = 60;
@@ -2610,6 +2614,14 @@ public int getWaitTimeoutS() {
         return waitTimeout;
     }
 
+    public boolean isEnableCompareForNull() {
+        return enableCompareForNull;
+    }
+
+    public void setEnableCompareForNull(boolean enableCompareForNull) {
+        this.enableCompareForNull = enableCompareForNull;
+    }
+
     public long getSqlMode() {
         return sqlMode;
     }

+    /**
+     * Ensure that enableCompareForNull is serialized correctly.
+     */
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        out.defaultWriteObject();
+        out.writeBoolean(enableCompareForNull);
+    }
+
+    /**
+     * Ensure that enableCompareForNull is deserialized correctly.
+     */
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+        in.defaultReadObject();
+        enableCompareForNull = in.readBoolean();
+    }

[sonarcloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[github-actions]

[Java-Extensions Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[FE Incremental Coverage Report]

❌ fail : 2 / 4 (50.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	com/starrocks/qe/SessionVariable.java	2	4	50.00%	[2622, 2623]

[github-actions]

[BE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)