MDL-88218: Add experimental SQLite support for Moodle WASM environments (4.5)

admin/environment.xml

@@ -4523,6 +4523,7 @@
       <VENDOR name="postgres" version="13" />
       <VENDOR name="mssql" version="14.0" />
       <VENDOR name="oracle" version="19" />
+      <VENDOR name="sqlite" version="3.0" />
     </DATABASE>
     <PHP version="8.1.0" level="required">
       <RESTRICT function="restrict_php_version_84" message="unsupportedphpversion84" />

lib/ddl/sqlite_sql_generator.php

@@ -73,8 +73,8 @@ class sqlite_sql_generator extends sql_generator {
     /**
      * Creates one new XMLDBmysql
      */
-    public function __construct($mdb) {
-        parent::__construct($mdb);
+    public function __construct($mdb, $temptables = null) {
+        parent::__construct($mdb, $temptables);
     }
 
     /**
@@ -460,4 +460,22 @@ public function addslashes($s) {
         $s = str_replace("'",  "''", $s);
         return $s;
     }
+
+    /**
+     * Given one correct xmldb_table, returns the SQL statements to create a
+     * temporary table (CREATE TEMPORARY TABLE ...), mirroring getCreateTableSQL.
+     *
+     * @param xmldb_table $xmldb_table The xmldb_table object instance.
+     * @return array of sql statements
+     */
+    public function getCreateTempTableSQL($xmldb_table) {
+        $this->temptables->add_temptable($xmldb_table->getName());
+        $sqlarr = parent::getCreateTableSQL($xmldb_table);
+        foreach ($sqlarr as $i => $sql) {
+            if (strpos($sql, 'CREATE TABLE ') === 0) {
+                $sqlarr[$i] = preg_replace('/^CREATE TABLE (.*)/s', 'CREATE TEMPORARY TABLE $1', $sql);
+            }
+        }
+        return $sqlarr;
+    }
 }

lib/dml/pdo_moodle_database.php

@@ -296,7 +296,7 @@ public function get_fieldset_sql($sql, ?array $params=null) {
         $rs = $this->get_recordset_sql($sql, $params);
         if (!$rs->valid()) {
             $rs->close(); // Not going to iterate (but exit), close rs
-            return false;
+            return array();
         }
         $result = array();
         foreach($rs as $value) {
@@ -326,7 +326,7 @@ public function get_records_sql($sql, ?array $params=null, $limitfrom=0, $limitn
         $rs = $this->get_recordset_sql($sql, $params, $limitfrom, $limitnum);
         if (!$rs->valid()) {
             $rs->close(); // Not going to iterate (but exit), close rs
-            return false;
+            return array();
         }
         $objects = array();
         foreach($rs as $value) {

lib/dml/sqlite3_pdo_moodle_database.php

@@ -208,7 +208,7 @@ protected function fetch_columns(string $table): array {
         }
         $createsql = $this->pdb->query($sql)->fetch();
         if (!$createsql) {
-            return false;
+            return array();
         }
         $createsql = $createsql['sql'];
 
@@ -287,7 +287,10 @@ protected function fetch_columns(string $table): array {
                 // trim extra quotes from text default values
                 $columninfo['default_value'] = substr($columninfo['default_value'], 1, -1);
             }
-            $structure[$columninfo['name']] = new database_column_info($columninfo);
+            // database_column_info reads its fields via object property access, so it must
+            // be given an object like the pgsql and mysqli drivers do; passing the raw array
+            // leaves every property (including ->name) null.
+            $structure[$columninfo['name']] = new database_column_info((object) $columninfo);
         }
 
         return $structure;
@@ -378,4 +381,20 @@ public function sql_concat_join($separator="' '", $elements=array()) {
     public function sql_bitxor($int1, $int2) {
         return '( ~' . $this->sql_bitand($int1, $int2) . ' & ' . $this->sql_bitor($int1, $int2) . ')';
     }
+
+    /**
+     * Connect, then initialise the temp-tables controller. Older cores (4.5)
+     * expect each driver to do this in connect(); without it $this->temptables
+     * stays null and the DDL generator fails during install.
+     *
+     * @return bool true on success
+     */
+    public function connect($dbhost, $dbuser, $dbpass, $dbname, $prefix, ?array $dboptions=null) {
+        $return = parent::connect($dbhost, $dbuser, $dbpass, $dbname, $prefix, $dboptions);
+        if ($this->temptables === null) {
+            require_once(__DIR__ . '/moodle_temptables.php');
+            $this->temptables = new moodle_temptables($this);
+        }
+        return $return;
+    }
 }