Eliminate SqlFragment, inline string concatenation in buildSqlString

Replace SqlFragment fluent chain with direct string concatenation in
Select, Update, and Delete. Removes 1 object allocation, ~13 method
calls, and 1 implode per render. SqlFragment class deleted — no
remaining callers.

Signed-off-by: Simon Mundy <simon.mundy@peptolab.com>

Author: simon-mundy

src/Sql/Delete.php

@@ -8,7 +8,6 @@
 use PhpDb\Adapter\Driver\DriverInterface;
 use PhpDb\Adapter\ParameterContainer;
 use PhpDb\Adapter\Platform\PlatformInterface;
-use PhpDb\Sql\Part\SqlFragment;
 use PhpDb\Sql\Part\SqlProcessor;
 use PhpDb\Sql\Part\From;
 use PhpDb\Sql\Part\Where as WherePart;
@@ -90,9 +89,13 @@ public function buildSqlString(
         $processor->setParamPrefix($this->processInfo['paramPrefix']);
         $sqlPlatform?->getTypeDecorator($this)?->prepare($this, $processor);
 
-        return (string) SqlFragment::of($this->getStatementKeyword())
-            ->part($this->table->toSql($processor))
-            ->part($this->where?->toSql($processor));
+        $sql = $this->getStatementKeyword() . ' ' . $this->table->toSql($processor);
+
+        if (null !== $part = $this->where?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        return $sql;
     }
 
     /**

src/Sql/Part/SqlFragment.php

@@ -15,7 +15,6 @@
 use PhpDb\Sql\Part\Offset;
 use PhpDb\Sql\Part\OrderBy;
 use PhpDb\Sql\Part\Quantifier;
-use PhpDb\Sql\Part\SqlFragment;
 use PhpDb\Sql\Part\SqlProcessor;
 use PhpDb\Sql\Part\Table;
 use PhpDb\Sql\Part\Where as WherePart;
@@ -387,18 +386,51 @@ public function buildSqlString(
         $sqlPlatform?->getTypeDecorator($this)?->prepare($this, $processor);
         $this->table->prepare($processor);
 
-        return (string) SqlFragment::of('SELECT')
-            ->part($this->quantifier?->toSql($processor))
-            ->part($this->table->columns()->toSql($processor))
-            ->part($this->table->from()->toSql($processor))
-            ->part($this->table->joins()?->toSql($processor))
-            ->part($this->where?->toSql($processor))
-            ->part($this->groupBy?->toSql($processor))
-            ->part($this->having?->toSql($processor))
-            ->part($this->orderBy?->toSql($processor))
-            ->part($this->limit?->toSql($processor))
-            ->part($this->offset?->toSql($processor))
-            ->wrap($this->combine?->toSql($processor));
+        $sql = 'SELECT';
+
+        if (null !== $part = $this->quantifier?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        $sql .= ' ' . $this->table->columns()->toSql($processor);
+
+        if (null !== $part = $this->table->from()->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->table->joins()?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->where?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->groupBy?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->having?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->orderBy?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->limit?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->offset?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        if (null !== $part = $this->combine?->toSql($processor)) {
+            $sql = '( ' . $sql . ' ) ' . $part;
+        }
+
+        return $sql;
     }
 
     /**

src/Sql/Select.php

@@ -10,7 +10,6 @@
 use PhpDb\Adapter\Platform\PlatformInterface;
 use PhpDb\Sql\Part\Joins as JoinsPart;
 use PhpDb\Sql\Part\Set as SetPart;
-use PhpDb\Sql\Part\SqlFragment;
 use PhpDb\Sql\Part\SqlProcessor;
 use PhpDb\Sql\Part\From;
 use PhpDb\Sql\Part\Where as WherePart;
@@ -136,11 +135,19 @@ public function buildSqlString(
         $processor->setParamPrefix($this->processInfo['paramPrefix']);
         $sqlPlatform?->getTypeDecorator($this)?->prepare($this, $processor);
 
-        return (string) SqlFragment::of($this->getStatementKeyword())
-            ->part($this->table->renderTable($processor))
-            ->part($this->joins?->toSql($processor))
-            ->part($this->set->toSql($processor))
-            ->part($this->where?->toSql($processor));
+        $sql = $this->getStatementKeyword() . ' ' . $this->table->renderTable($processor);
+
+        if (null !== $part = $this->joins?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        $sql .= ' ' . $this->set->toSql($processor);
+
+        if (null !== $part = $this->where?->toSql($processor)) {
+            $sql .= ' ' . $part;
+        }
+
+        return $sql;
     }
 
     /**