Address remaining CodeRabbit review feedback (rounds 2-3)

- Guard against empty array filter values producing invalid IN () SQL;
  short-circuit to match-nothing condition instead
- Use +0 instead of (int) cast for query result values to preserve
  fractional aggregates (e.g. avg returns floats)
- Add retry with exponential backoff to insert(), matching the existing
  read-path retry in query(), so transient network errors or 5xx/429
  responses don't silently drop entire batches

https://claude.ai/code/session_01UCN4sKD3Zkdbimn3QgTHSB

Author: claude

src/Usage/Adapter/ClickHouse.php

@@ -614,6 +614,11 @@ private function buildFilters(array $filters, array &$params, int &$paramCounter
             $escaped = $this->esc($key);
 
             if (is_array($value)) {
+                if (empty($value)) {
+                    // Empty IN() is invalid SQL; match nothing
+                    $conditions[] = '0';
+                    continue;
+                }
                 $inParts = [];
                 foreach ($value as $v) {
                     $pn = 'p_' . $paramCounter++;
@@ -695,9 +700,9 @@ private function parseRows(string $result): array
                 $row['tags'] = json_decode($row['tags'], true) ?? [];
             }
 
-            // Cast numeric fields
+            // Cast numeric fields (use +0 to preserve decimals from avg/float aggregates)
             if (isset($row['value'])) {
-                $row['value'] = (int) $row['value'];
+                $row['value'] = $row['value'] + 0;
             }
             if (isset($row['count'])) {
                 $row['count'] = (int) $row['count'];
@@ -802,10 +807,6 @@ private function insert(string $table, array $rows): void
         $queryParams = ['query' => "INSERT INTO {$escaped} FORMAT JSONEachRow"];
         $url = "{$scheme}://{$this->host}:{$this->port}/?" . http_build_query($queryParams);
 
-        $this->client->addHeader('X-ClickHouse-Database', $this->database);
-        $this->client->addHeader('Content-Type', 'application/x-ndjson');
-        $this->client->addHeader('Connection', 'keep-alive');
-
         $jsonRows = array_map(function ($row) {
             $encoded = json_encode($row);
             if ($encoded === false) {
@@ -816,22 +817,45 @@ private function insert(string $table, array $rows): void
 
         $body = implode("\n", $jsonRows);
 
-        try {
-            $response = $this->client->fetch(
-                url: $url,
-                method: Client::METHOD_POST,
-                body: $body,
-            );
-
-            $httpCode = $response->getStatusCode();
-            if ($httpCode !== 200) {
-                $responseBody = $response->getBody();
-                $responseBody = is_string($responseBody) ? $responseBody : '';
-                throw new Exception("ClickHouse insert HTTP {$httpCode}: {$responseBody}");
+        $attempt = 0;
+        $lastException = null;
+
+        while ($attempt <= $this->maxRetries) {
+            try {
+                $this->client->addHeader('X-ClickHouse-Database', $this->database);
+                $this->client->addHeader('Content-Type', 'application/x-ndjson');
+                $this->client->addHeader('Connection', 'keep-alive');
+
+                try {
+                    $response = $this->client->fetch(
+                        url: $url,
+                        method: Client::METHOD_POST,
+                        body: $body,
+                    );
+                } finally {
+                    $this->client->removeHeader('Content-Type');
+                }
+
+                $httpCode = $response->getStatusCode();
+                if ($httpCode !== 200) {
+                    $responseBody = $response->getBody();
+                    $responseBody = is_string($responseBody) ? $responseBody : '';
+                    throw new Exception("ClickHouse insert HTTP {$httpCode}: {$responseBody}");
+                }
+
+                return;
+            } catch (Exception $e) {
+                $lastException = $e;
+                if ($attempt < $this->maxRetries && $this->isRetryable($e)) {
+                    $attempt++;
+                    usleep($this->retryDelay * (2 ** ($attempt - 1)) * 1000);
+                    continue;
+                }
+                throw $e;
             }
-        } finally {
-            $this->client->removeHeader('Content-Type');
         }
+
+        throw $lastException ?? new Exception('Unknown insert error');
     }
 
     // ─── Internal: Utilities ─────────────────────────────────────────