Record ALTER TABLE DROP COLUMN in information schema

Author: JanJakes

wp-includes/sqlite-ast/class-wp-sqlite-information-schema-builder.php

@@ -484,6 +484,16 @@ public function record_alter_table( WP_Parser_Node $node ): void {
 				);
 				continue;
 			}
+
+			// DROP
+			if ( WP_MySQL_Lexer::DROP_SYMBOL === $first_token->id ) {
+				// DROP [COLUMN]
+				$column_ref = $action->get_child_node( 'columnInternalRef' );
+				if ( null !== $column_ref ) {
+					$name = $this->get_value( $column_ref );
+					$this->record_drop_column( $table_name, $name );
+				}
+			}
 		}
 	}
 
@@ -554,6 +564,41 @@ private function record_modify_column(
 		$this->record_change_column( $table_name, $column_name, $column_name, $node );
 	}
 
+	private function record_drop_column( $table_name, $column_name ): void {
+		$this->delete_values(
+			'_mysql_information_schema_columns',
+			array(
+				'table_name'  => $table_name,
+				'column_name' => $column_name,
+			)
+		);
+
+		/**
+		 * From MySQL documentation:
+		 *
+		 *   If columns are dropped from a table, the columns are also removed
+		 *   from any index of which they are a part. If all columns that make up
+		 *   an index are dropped, the index is dropped as well.
+		 *
+		 * This means we need to remove the records from the STATISTICS table,
+		 * renumber the SEQ_IN_INDEX values, and resync the column key info.
+		 *
+		 * See:
+		 *   - https://dev.mysql.com/doc/refman/8.4/en/alter-table.html
+		 */
+		$this->delete_values(
+			'_mysql_information_schema_statistics',
+			array(
+				'table_name'  => $table_name,
+				'column_name' => $column_name,
+			)
+		);
+
+		// @TODO: Renumber SEQ_IN_INDEX values.
+
+		$this->sync_column_key_info( $table_name );
+	}
+
 	private function record_add_constraint( string $table_name, WP_Parser_Node $node ): void {
 		// Get first constraint keyword.
 		$children = $node->get_children();
@@ -1416,6 +1461,21 @@ private function update_values( string $table_name, array $data, array $where ):
 		);
 	}
 
+	private function delete_values( string $table_name, array $where ): void {
+		$where_clause = array();
+		foreach ( $where as $column => $value ) {
+			$where_clause[] = $column . ' = ?';
+		}
+
+		$this->query(
+			'
+				DELETE FROM ' . $table_name . '
+				WHERE ' . implode( ' AND ', $where_clause ) . '
+			',
+			array_values( $where )
+		);
+	}
+
 	/**
 	 * @param string $query
 	 * @param array $params