"limit" and "offset" support, even in 11g and earlier

src/OracleCompiler.php

@@ -19,15 +19,131 @@
  */
 namespace Cake\Oracle;
 
+use Cake\Database\ExpressionInterface;
 use Cake\Database\QueryCompiler;
 
 class OracleCompiler extends QueryCompiler
 {
     /**
      * {@inheritDoc}
      */
+    protected $_templates = [
+        'delete' => 'DELETE',
+        'update' => 'UPDATE %s',
+        'where' => ' WHERE %s',
+        'group' => ' GROUP BY %s ',
+        'having' => ' HAVING %s ',
+        'order' => ' %s'
+    ];
+
+    /**
+     * The list of query clauses to traverse for generating a SELECT statement
+     * Since Oracle (before version 12c) does not have built-in offset and limit,
+     * we need to add some funky wrapper sql. So we traverse "offset" and "limit"
+     * *before* "select", and also tweak the "epilog" as necessary
+     * Please let me know if there's a better way to add "wrapper" sql
+     * than this :)
+     *
+     * @var array
+     */
     protected $_selectParts = [
+        'offset', 'limit',
         'select', 'from', 'join', 'where', 'group', 'having', 'order', 'union',
         'epilog'
     ];
+
+    /**
+     * Generates the OFFSET part of a SQL query
+     *
+     * @param int $offset the offset clause
+     * @param \Cake\Database\Query $query The query that is being compiled
+     * @return string
+     */
+    protected function _buildOffsetPart($offset, $query)
+    {
+        if (empty($offset) || intval($offset) < 1) {
+            return '';
+        }
+
+        $origEpilog = $query->clause('epilog');
+        $limit = intval($query->clause('limit'));
+        if (empty($limit)) {
+            $offsetEnd = ') WHERE ROWNUM > :SNELG_FETCH_OFFSET';
+        } else {
+            $offsetEnd = ') WHERE snelg_oracle_sub_rnum > :SNELG_FETCH_OFFSET';
+        }
+
+        $query->bind(':SNELG_FETCH_OFFSET', $offset);
+        $query->epilog([
+            'snelgOracleOrigEpilog' => $origEpilog,
+            'snelgOracleEndWrap' => $offsetEnd
+        ]);
+
+        return 'SELECT * FROM (';
+    }
+
+    /**
+     * Generates the LIMIT part of a SQL query
+     *
+     * @param int $limit the limit clause
+     * @param \Cake\Database\Query $query The query that is being compiled
+     * @return string
+     */
+    protected function _buildLimitPart($limit, $query)
+    {
+        if (empty($limit) || intval($limit) < 1) {
+            return '';
+        }
+
+        $offset = intval($query->clause('offset'));
+        $endRow = $offset + $limit;
+        $origEpilog = $query->clause('epilog');
+        $limitEnd = ') a WHERE ROWNUM <= :SNELG_MAX_ROW_TO_FETCH';
+        if (!empty($offset) && $offset > 0) {
+            $limitEnd .= ' ' . $origEpilog['snelgOracleEndWrap'];
+            $origEpilog = $origEpilog['snelgOracleOrigEpilog'];
+        }
+
+        $query->bind(':SNELG_MAX_ROW_TO_FETCH', $endRow);
+        $query->epilog([
+            'snelgOracleOrigEpilog' => $origEpilog,
+            'snelgOracleEndWrap' => $limitEnd
+        ]);
+
+        return 'SELECT /*+ FIRST_ROWS(n) */ a.*, ROWNUM snelg_oracle_sub_rnum FROM (';
+    }
+
+    /**
+     * Generates the EPILOG part of a SQL query, including special handling
+     * if we added offset and/or limit wrappers earlier
+     *
+     * @param mixed $epilog the epilog clause
+     * @param \Cake\Database\Query $query The query that is being compiled
+     * @param \Cake\Database\ValueBinder $generator The placeholder and value binder object
+     * @return string
+     */
+    protected function _buildEpilogPart($epilog, $query, $generator)
+    {
+        if (!is_array($epilog) || !array_key_exists('snelgOracleOrigEpilog', $epilog)) {
+            $origEpilog = $epilog;
+        } else {
+            //We wrapped the original epilog, which might have been an
+            //ExpressionInterface instead of a simple string
+            $origEpilog = $epilog['snelgOracleOrigEpilog'];
+        }
+
+        //Duplicate original _sqlCompiler functionality...
+        if ($origEpilog instanceof ExpressionInterface) {
+            $origEpilog = [$origEpilog->sql($generator)];
+        }
+        $origEpilog = $this->_stringifyExpressions((array)$origEpilog, $generator);
+        $epilogSql = sprintf(' %s', implode(', ', $origEpilog));
+
+        //And then add our own wrapper
+        if (is_array($epilog) && !empty($epilog['snelgOracleEndWrap'])) {
+            $epilogSql .= ' ' . $epilog['snelgOracleEndWrap'];
+        }
+
+        return $epilogSql;
+    }
 }