[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();
+    }

[trueeyu]

@Mergifyio rebase main

[mergify]

rebase main

✅ Branch has been successfully rebased

[sonarqubecloud]

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]

[BE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[FE Incremental Coverage Report]

✅ pass : 2 / 2 (100.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	com/starrocks/qe/SessionVariable.java	2	2	100.00%	[]

[kangkaisen]

I think I should let the user modify the SQL rather than support this unreasonable behavior.

[even986025158]

I think I should let the user modify the SQL rather than support this unreasonable behavior.

We actually hope that users can modify SQL, but due to some historical reasons, a large number of this type of SQL need to be modified. Users think that the workload is huge and there are certain risks in modification, so they hope that we support this feature. Moreover, for SR, supporting this parameter can meet more user scenarios, which is actually beneficial. In addition, it does not affect the original query by default. Users who need this feature can only enable it through parameters. If some users are unwilling to use SR because of this situation, I think this is actually a lose-lose result, so I think it is more reasonable to support this behavior through parameters.