Revert Quantifier/Table::prepare/public-field changes that regressed perf

The public field visibility changes on Columns and From, combined with
the Quantifier simplification and Table::prepare inlining, caused a
regression from 19μs to 28μs on the complex select benchmark.
Reverting to the state after the ColumnRef/OrderSpec commit.

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

Author: simon-mundy

src/Sql/Part/Columns.php

@@ -31,13 +31,15 @@ class Columns extends AbstractPart
     /** @var array Raw columns for getRawState() backward compatibility */
     private array $rawColumns = [Select::SQL_STAR];
 
-    public bool $prefixColumnsWithTable = true;
+    private bool $prefixColumnsWithTable = true;
 
-    /** @var string Resolved table prefix (e.g. "table".) — set by Table::prepare() */
-    public string $fromTablePrefix = '';
+    /**
+     * Set during preparePartsForBuild -- the resolved table prefix (e.g. "table".)
+     */
+    private string $fromTablePrefix = '';
 
-    /** @var JoinSpec[] Join specs — set by Table::prepare() */
-    public array $joinSpecs = [];
+    /** @var JoinSpec[] Join specs for column resolution */
+    private array $joinSpecs = [];
 
     public function __construct()
     {
@@ -166,6 +168,26 @@ public function getPrefixColumnsWithTable(): bool
         return $this->prefixColumnsWithTable;
     }
 
+    /**
+     * Set the table prefix for column resolution (e.g. "table".)
+     */
+    public function setFromTablePrefix(string $prefix): static
+    {
+        $this->fromTablePrefix = $prefix;
+        return $this;
+    }
+
+    /**
+     * Set join specs for column resolution during rendering.
+     *
+     * @param JoinSpec[] $specs
+     */
+    public function setJoinSpecs(array $specs): static
+    {
+        $this->joinSpecs = $specs;
+        return $this;
+    }
+
     /**
      * Normalize the raw columns array into ColumnRef[].
      */

src/Sql/Part/From.php

@@ -14,7 +14,7 @@
  */
 class From extends AbstractPart
 {
-    public ?TableRef $ref = null;
+    private ?TableRef $ref = null;
 
     private ?string $resolvedTable = null;
 

src/Sql/Part/Quantifier.php

@@ -4,25 +4,32 @@
 
 namespace PhpDb\Sql\Part;
 
+use PhpDb\Sql\Argument\Literal;
+use PhpDb\Sql\Argument\Select as SelectArgument;
+use PhpDb\Sql\ArgumentInterface;
+use PhpDb\Sql\ArgumentType;
 use PhpDb\Sql\ExpressionInterface;
+use ValueError;
 
-use function is_string;
-
+/**
+ * Holds and renders a SELECT quantifier (DISTINCT, ALL, or expression).
+ * Normalizes input to ArgumentInterface at set time.
+ */
 class Quantifier extends AbstractPart
 {
-    private ExpressionInterface|string|null $quantifier = null;
+    private ?ArgumentInterface $quantifier = null;
 
     public function toSql(SqlProcessor $processor): ?string
     {
         if ($this->quantifier === null) {
             return null;
         }
 
-        if (is_string($this->quantifier)) {
-            return $this->quantifier;
-        }
-
-        return $processor->renderExpression($this->quantifier, 'quantifier');
+        return match ($this->quantifier->getType()) {
+            ArgumentType::Literal => $this->quantifier->getValue(),
+            ArgumentType::Select  => $processor->renderExpression($this->quantifier->getValue(), 'quantifier'),
+            default => throw new ValueError('Unexpected ArgumentType: ' . $this->quantifier->getType()->name),
+        };
     }
 
     public function isEmpty(): bool
@@ -32,12 +39,25 @@ public function isEmpty(): bool
 
     public function set(string|ExpressionInterface|null $quantifier): static
     {
-        $this->quantifier = $quantifier;
+        if ($quantifier === null) {
+            $this->quantifier = null;
+        } elseif ($quantifier instanceof ExpressionInterface) {
+            $this->quantifier = new SelectArgument($quantifier);
+        } else {
+            $this->quantifier = new Literal($quantifier);
+        }
         return $this;
     }
 
+    /**
+     * Reconstruct the original format for getRawState() compatibility.
+     */
     public function get(): string|ExpressionInterface|null
     {
-        return $this->quantifier;
+        if ($this->quantifier === null) {
+            return null;
+        }
+
+        return $this->quantifier->getValue();
     }
 }

src/Sql/Part/Table.php

@@ -22,7 +22,7 @@ class Table
 {
     private From $from;
     private Columns $columns;
-    private ?Joins $joins            = null;
+    private ?Joins $joins = null;
     private ?int $preparedPlatformId = null;
 
     /** Backward-compat model exposed via getRawState / __get */
@@ -50,7 +50,7 @@ public function getFrom(): string|array|TableIdentifier|Select|null
 
     public function hasFrom(): bool
     {
-        return ! $this->from->isEmpty();
+        return !$this->from->isEmpty();
     }
 
     public function resetFrom(): static
@@ -106,12 +106,12 @@ public function join(
 
     public function hasJoins(): bool
     {
-        return $this->joins !== null && ! $this->joins->isEmpty();
+        return $this->joins !== null && !$this->joins->isEmpty();
     }
 
     public function resetJoins(): static
     {
-        $this->joins              = null;
+        $this->joins = null;
         $this->preparedPlatformId = null;
         return $this;
     }
@@ -125,10 +125,12 @@ public function prepare(SqlProcessor $processor): void
             return;
         }
 
-        $this->columns->fromTablePrefix = $this->columns->prefixColumnsWithTable && $this->from->ref !== null
-            ? $this->from->getQuotedPrefix($processor)
-            : '';
-        $this->columns->joinSpecs = $this->joins?->getSpecs() ?? [];
+        if ($this->columns->getPrefixColumnsWithTable() && !$this->from->isEmpty()) {
+            $this->columns->setFromTablePrefix($this->from->getQuotedPrefix($processor));
+        } else {
+            $this->columns->setFromTablePrefix('');
+        }
+        $this->columns->setJoinSpecs($this->joins !== null ? $this->joins->getSpecs() : []);
         $this->preparedPlatformId = $platformId;
     }