fix: correct tag filter operator handling for "No Tag" and "Any Tag"

The filter system ignored the operator (= vs !=) when generating SQL
for the special tag values "No Tag" (0) and "Any Tag" (-1).

In PHP (FilterTerm.php), "Tag != Any Tag" produced EXISTS instead of
NOT EXISTS, returning events WITH tags instead of events WITHOUT tags.

In Perl (Filter.pm), != was not handled as a special case and fell
through to generic SQL (T.Id != -1), which excluded events with no
tags because LEFT JOIN produces NULL and NULL != -1 evaluates to
UNKNOWN in SQL. Additionally, T.Id was unconditionally prepended for
all tag values, producing invalid SQL (T.IdEXISTS) for the special
cases that use EXISTS/NOT EXISTS subqueries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pliablepixels

scripts/ZoneMinder/lib/ZoneMinder/Filter.pm

@@ -166,7 +166,11 @@ sub Sql {
           $term->{op} = 'EXISTS';
         } elsif ( $term->{attr} eq 'Tags' ) {
           $fields .= ', (SELECT GROUP_CONCAT(Name) FROM Tags WHERE Id IN (SELECT TagId FROM Events_Tags WHERE Events_Tags.EventId=E.Id)) As Tags';
-          $self->{Sql} .= 'T.Id';
+          # Don't prepend T.Id for special tag values (0="No Tag", -1="Any Tag")
+          # as those use EXISTS/NOT EXISTS subqueries instead
+          if (!defined($term->{val}) or ($term->{val} ne '0' and $term->{val} ne '-1')) {
+            $self->{Sql} .= 'T.Id';
+          }
           $from .= ' LEFT JOIN Events_Tags AS ET ON E.Id = ET.EventId LEFT JOIN Tags AS T ON T.Id = ET.TagId';
         } elsif ( $term->{attr} =~ /^Monitor/ ) {
           if (!($fields =~ /MonitorName/)) {
@@ -316,7 +320,23 @@ sub Sql {
           } # end foreach temp_value
 
           if ( $term->{op} ) {
-            if ( $term->{op} eq '=~' ) {
+            # Handle special tag values before generic operators to avoid
+            # LEFT JOIN NULL comparison issues with EXISTS/NOT EXISTS
+            if ( $term->{attr} eq 'Tags' and $term->{val} eq '0' ) {
+              # "No Tag": = means no tags (NOT EXISTS), != means has tags (EXISTS)
+              if ($term->{op} eq '!=' or $term->{op} eq 'IS NOT') {
+                $self->{Sql} .= 'EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
+              } else {
+                $self->{Sql} .= 'NOT EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
+              }
+            } elsif ( $term->{attr} eq 'Tags' and $term->{val} eq '-1' ) {
+              # "Any Tag": = means has tags (EXISTS), != means no tags (NOT EXISTS)
+              if ($term->{op} eq '!=' or $term->{op} eq 'IS NOT') {
+                $self->{Sql} .= 'NOT EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
+              } else {
+                $self->{Sql} .= 'EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
+              }
+            } elsif ( $term->{op} eq '=~' ) {
               $self->{Sql} .= ' REGEXP '.$value;
             } elsif ( $term->{op} eq '!~' ) {
               $self->{Sql} .= ' NOT REGEXP '.$value;
@@ -346,10 +366,6 @@ sub Sql {
               $self->{Sql} .= ' LIKE '.$value;
             } elsif ( $term->{op} eq 'NOT LIKE' ) {
               $self->{Sql} .= ' NOT LIKE '.$value;
-            } elsif ( $term->{attr} eq 'Tags' and ($term->{op} eq 'LIKE' or $term->{op} eq 'IS') and $term->{val} eq 0) {
-              $self->{Sql} .= 'NOT EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
-            } elsif ( $term->{attr} eq 'Tags' and ($term->{op} eq '=' or $term->{op} eq 'IS') and $term->{val} eq -1) {
-              $self->{Sql} .= 'EXISTS (SELECT NULL FROM `Events_Tags` AS ET WHERE ET.EventId = E.Id)';
             } else {
               $self->{Sql} .= ' '.$term->{op}.' '.$value;
             }

web/includes/FilterTerm.php

@@ -344,9 +344,19 @@ public function sql() {
       }
       $sql .= '('.implode(' OR ', $subterms).')';
     } elseif (($this->attr === 'Tags') && ($values[0] === "'0'")) {
-      $sql .= 'NOT EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
+      // "No Tag": = means no tags (NOT EXISTS), != means has tags (EXISTS)
+      if ($this->op === '!=') {
+        $sql .= 'EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
+      } else {
+        $sql .= 'NOT EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
+      }
     } elseif (($this->attr === 'Tags') && ($values[0] === "'-1'")) {
-      $sql .= 'EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
+      // "Any Tag": = means has tags (EXISTS), != means no tags (NOT EXISTS)
+      if ($this->op === '!=') {
+        $sql .= 'NOT EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
+      } else {
+        $sql .= 'EXISTS (SELECT NULL FROM Events_Tags AS ET WHERE ET.EventId = E.Id)';
+      }
     } else {
       $sql .= $this->sql_attr();
       if ($this->collate) $sql .= ' COLLATE '.$this->collate;