Merge pull request #86 from keboola/mj-teradata-platform

TER-18 Table preview filters

Author: martinjunger

src/Connection/Teradata/TeradataPlatform.php

@@ -6,6 +6,8 @@
 
 use Doctrine\DBAL\Platforms\AbstractPlatform;
 use Exception;
+use LogicException;
+use RuntimeException;
 
 class TeradataPlatform extends AbstractPlatform
 {
@@ -95,4 +97,52 @@ public function getCurrentDatabaseExpression(): string
         throw new Exception('method is not implemented yet');
         // TODO: Implement getCurrentDatabaseExpression() method.
     }
+
+    /**
+     * {@inheritDoc}
+     */
+    protected function doModifyLimitQuery($query, $limit, $offset): string
+    {
+        if (($limit === null || $limit === 0) && $offset <= 0) {
+            return $query;
+        }
+
+        if (preg_match('/^\s*SELECT\s+DISTINCT/im', $query) > 0) {
+            /** @codingStandardsIgnoreStart */
+            /*
+            You cannot specify the TOP n operator in any of these SQL statements or statement components:
+              - Correlated subquery
+              - Subquery in a search condition
+              - CREATE JOIN INDEX
+              - CREATE HASH INDEX
+              - Seed statement or recursive statement in a CREATE RECURSIVE VIEW statement or WITH RECURSIVE statement modifier
+              - Subselects of set operations.
+            You cannot specify these options in a SELECT statement that specifies the TOP n operator:
+              - DISTINCT option
+              - QUALIFY clause
+              - SAMPLE clause
+              - WITH clause
+              - This restriction refers to the WITH clause you can specify for summary lines and breaks. See WITH Clause. The nonrecursive WITH statement modifier that can precede the SELECT keyword can be included in statements that also specify the TOP n operator. See WITH Modifier.
+              - ORDER BY clause where the sort expression is an ordered analytical function.
+            See https://www.docs.teradata.com/r/Teradata-VantageTM-SQL-Data-Manipulation-Language/July-2021/SELECT-Statements/Select-List-Syntax/TOP-Clause/Usage-Notes/Rules-and-Restrictions-for-the-TOP-n-Operator
+            */
+            /** @codingStandardsIgnoreEnd */
+            // skip limit
+        } else {
+            $query = preg_replace(
+                '/^(\s*SELECT\b)/im',
+                sprintf('$1 TOP %s', $limit),
+                $query
+            );
+            if ($query === null) {
+                throw new RuntimeException('Adding LIMIT to SQL retunrs error.');
+            }
+        }
+
+        if ($offset > 0) {
+            throw new LogicException('Support for OFFSET not implemented yet.');
+        }
+
+        return $query;
+    }
 }