ENH Allow disabling/dropping indexes via config

Author: GuySartorelli

src/ORM/Connect/DBSchemaManager.php

@@ -314,7 +314,7 @@ public function transAlterField($table, $field, $schema)
      *
      * @param string $table Name of the table to hold this index
      * @param string $index Name of the index to update
-     * @param array $schema Already parsed index specification
+     * @param array|false $schema Already parsed index specification, or false to drop the index.
      */
     public function transAlterIndex($table, $index, $schema)
     {
@@ -431,7 +431,11 @@ public function requireTable(
         // Create custom indexes
         if ($indexSchema) {
             foreach ($indexSchema as $indexName => $indexSpec) {
-                $this->requireIndex($table, $indexName, $indexSpec);
+                if ($indexSpec === false) {
+                    $this->dontRequireIndex($table, $indexName);
+                } else {
+                    $this->requireIndex($table, $indexName, $indexSpec);
+                }
             }
         }
 
@@ -529,6 +533,28 @@ public function requireIndex($table, $index, $spec)
         }
     }
 
+    public function dontRequireIndex(string $table, string $index): void
+    {
+        // Skip if this is a new table, since it just won't have that index
+        $newTable = !isset($this->tableList[strtolower($table)]);
+        if ($newTable) {
+            return;
+        }
+
+        $indexKey = $this->indexKey($table, $index, []);
+        $indexList = $this->indexList($table);
+        // Drop the index if it exists
+        if (isset($indexList[$indexKey])) {
+            $oldSpec = $indexList[$indexKey];
+            $oldSpecString = $this->convertIndexSpec($oldSpec);
+            $this->transAlterIndex($table, $index, false);
+            $this->alterationMessage(
+                "Index $table.$index: dropped <i class=\"build-info-before\">(from $oldSpecString)</i>",
+                "deleted"
+            );
+        }
+    }
+
     /**
      * Splits a spec string safely, considering quoted columns, whitespace,
      * and cleaning brackets

src/ORM/Connect/MySQLSchemaManager.php

@@ -93,7 +93,9 @@ public function alterTable(
         if ($alteredIndexes) {
             foreach ($alteredIndexes as $k => $v) {
                 $alterList[] = "DROP INDEX \"$k\"";
-                $alterList[] = "ADD " . $this->getIndexSqlDefinition($k, $v);
+                if ($v !== false) {
+                    $alterList[] = "ADD " . $this->getIndexSqlDefinition($k, $v);
+                }
             }
         }
 

src/ORM/DataObjectSchema.php

@@ -629,7 +629,7 @@ protected function buildCustomDatabaseIndexes($class)
                         var_export($indexSpec['columns'], true)
                     ));
                 }
-            } else {
+            } elseif ($indexSpec !== false) {
                 $indexSpec = [
                     'type' => 'index',
                     'columns' => [$indexName],