feat : add DatabaseService for PostgreSQL metrics

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/Service/DatabaseService.php

@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use Doctrine\DBAL\Connection;
+
+final class DatabaseService
+{
+    public function __construct(
+        private readonly Connection $connection,
+    ) {}
+
+    /**
+     * @return array{connected: bool, name: string, size: string, tableCount: int, activeConnections: int, cacheHitRatio: float, largestTable: string}
+     */
+    public function getDatabaseInfo(string $databaseName): array
+    {
+        $fallback = [
+            'connected' => false,
+            'name' => $databaseName,
+            'size' => '',
+            'tableCount' => 0,
+            'activeConnections' => 0,
+            'cacheHitRatio' => 0.0,
+            'largestTable' => '',
+        ];
+
+        try {
+            // Check database exists
+            $exists = $this->connection->fetchOne(
+                'SELECT 1 FROM pg_database WHERE datname = :dbname',
+                ['dbname' => $databaseName]
+            );
+
+            if (!$exists) {
+                return $fallback;
+            }
+
+            // Database size
+            $sizeBytes = (int) $this->connection->fetchOne(
+                'SELECT pg_database_size(:dbname)',
+                ['dbname' => $databaseName]
+            );
+            $size = $this->formatBytes($sizeBytes);
+
+            // Table count
+            $tableCount = (int) $this->connection->fetchOne(
+                "SELECT count(*) FROM information_schema.tables WHERE table_schema = 'public' AND table_catalog = :dbname",
+                ['dbname' => $databaseName]
+            );
+
+            // Active connections
+            $activeConnections = (int) $this->connection->fetchOne(
+                'SELECT count(*) FROM pg_stat_activity WHERE datname = :dbname',
+                ['dbname' => $databaseName]
+            );
+
+            // Cache hit ratio
+            $cacheHitRatio = (float) ($this->connection->fetchOne(
+                'SELECT round(100.0 * sum(blks_hit) / nullif(sum(blks_hit + blks_read), 0), 2) FROM pg_stat_database WHERE datname = :dbname',
+                ['dbname' => $databaseName]
+            ) ?? 0);
+
+            // Largest table — requires querying the target database catalog
+            $largestTable = $this->fetchLargestTable($databaseName);
+
+            return [
+                'connected' => true,
+                'name' => $databaseName,
+                'size' => $size,
+                'tableCount' => $tableCount,
+                'activeConnections' => $activeConnections,
+                'cacheHitRatio' => $cacheHitRatio,
+                'largestTable' => $largestTable,
+            ];
+        } catch (\Throwable) {
+            return $fallback;
+        }
+    }
+
+    private function fetchLargestTable(string $databaseName): string
+    {
+        try {
+            $row = $this->connection->fetchAssociative(
+                "SELECT relname, pg_total_relation_size(c.oid) as total_size
+                 FROM pg_catalog.pg_class c
+                 JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
+                 WHERE n.nspname = 'public' AND c.relkind = 'r'
+                   AND c.relowner = (SELECT oid FROM pg_roles WHERE rolname = current_user)
+                 ORDER BY pg_total_relation_size(c.oid) DESC
+                 LIMIT 1"
+            );
+
+            if (!$row) {
+                return '-';
+            }
+
+            return $row['relname'] . ' (' . $this->formatBytes((int) $row['total_size']) . ')';
+        } catch (\Throwable) {
+            return '-';
+        }
+    }
+
+    private function formatBytes(int $bytes): string
+    {
+        if ($bytes < 1024) {
+            return $bytes . ' B';
+        }
+
+        $units = ['KB', 'MB', 'GB', 'TB'];
+        $value = (float) $bytes;
+
+        foreach ($units as $unit) {
+            $value /= 1024;
+            if ($value < 1024) {
+                return round($value, 1) . ' ' . $unit;
+            }
+        }
+
+        return round($value, 1) . ' TB';
+    }
+}