diff --git a/src/db/Capacitor.php b/src/db/Capacitor.php
index 6a41d5a..b7c7155 100644
--- a/src/db/Capacitor.php
+++ b/src/db/Capacitor.php
@@ -66,17 +66,22 @@ class Capacitor implements ITransactor {
   }
 
   function beginTransaction(?callable $func=null, bool $commit=true): void {
-    if ($this->subManageTransactions === null && $this->subChannels !== null) {
-      foreach ($this->subChannels as $channel) {
-        $name = $channel->getName();
-        $this->subManageTransactions ??= [];
-        if (!array_key_exists($name, $this->subManageTransactions)) {
-          $this->subManageTransactions[$name] = $channel->isManageTransactions();
+    $db = $this->db();
+    if ($this->subChannels !== null) {
+      # on gère des subchannels: ne débuter la transaction que si ce n'est déjà fait
+      if ($this->subManageTransactions === null) {
+        foreach ($this->subChannels as $channel) {
+          $name = $channel->getName();
+          $this->subManageTransactions ??= [];
+          if (!array_key_exists($name, $this->subManageTransactions)) {
+            $this->subManageTransactions[$name] = $channel->isManageTransactions();
+          }
+          $channel->setManageTransactions(false);
         }
-        $channel->setManageTransactions(false);
+        if (!$db->inTransaction()) $db->beginTransaction();
       }
-      $db = $this->db();
-      if (!$db->inTransaction()) $db->beginTransaction();
+    } elseif (!$db->inTransaction()) {
+      $db->beginTransaction();
     }
     if ($func !== null) {
       $commited = false;
@@ -105,13 +110,13 @@ class Capacitor implements ITransactor {
   function commit(): void {
     $this->beforeEndTransaction();
     $db = $this->db();
-    if ($db->inTransaction()) $this->db()->commit();
+    if ($db->inTransaction()) $db->commit();
   }
 
   function rollback(): void {
     $this->beforeEndTransaction();
     $db = $this->db();
-    if ($db->inTransaction()) $this->db()->rollback();
+    if ($db->inTransaction()) $db->rollback();
   }
 
   function getCreateSql(): string {
@@ -131,7 +136,7 @@ class Capacitor implements ITransactor {
   }
 
   function charge($item, $func=null, ?array $args=null, ?array &$values=null): int {
-    $this->beginTransaction();
+    if ($this->subChannels !== null) $this->beginTransaction();
     return $this->storage->_charge($this->channel, $item, $func, $args, $values);
   }
 
@@ -152,12 +157,12 @@ class Capacitor implements ITransactor {
   }
 
   function each($filter, $func=null, ?array $args=null, ?int &$updated=null): int {
-    $this->beginTransaction();
+    if ($this->subChannels !== null) $this->beginTransaction();
     return $this->storage->_each($this->channel, $filter, $func, $args, $updated);
   }
 
   function delete($filter, $func=null, ?array $args=null): int {
-    $this->beginTransaction();
+    if ($this->subChannels !== null) $this->beginTransaction();
     return $this->storage->_delete($this->channel, $filter, $func, $args);
   }
 
diff --git a/src/db/CapacitorChannel.php b/src/db/CapacitorChannel.php
index 5da0497..bea0b23 100644
--- a/src/db/CapacitorChannel.php
+++ b/src/db/CapacitorChannel.php
@@ -71,18 +71,6 @@ class CapacitorChannel {
     return $this->tableName;
   }
 
-  /**
-   * @var Capacitor|null instance de Capacitor par laquelle cette instance est
-   * utilisée. ça peut être utile pour implémenter des workflows centrés sur le
-   * channel
-   */
-  protected ?Capacitor $capacitor;
-
-  function setCapacitor(Capacitor $capacitor): self {
-    $this->capacitor = $capacitor;
-    return $this;
-  }
-
   /**
    * @var bool indiquer si les modifications de each doivent être gérées dans
    * une transaction. si false, l'utilisateur doit lui même gérer la
@@ -326,4 +314,50 @@ class CapacitorChannel {
     return true;
   }
   const onDelete = "->".[self::class, "onDelete"][1];
+
+  #############################################################################
+  # Méthodes déléguées pour des workflows centrés sur le channel
+
+  /**
+   * @var Capacitor|null instance de Capacitor par laquelle cette instance est
+   * utilisée
+   */
+  protected ?Capacitor $capacitor;
+
+  function getCapacitor(): ?Capacitor {
+    return $this->capacitor;
+  }
+
+  function setCapacitor(Capacitor $capacitor): self {
+    $this->capacitor = $capacitor;
+    return $this;
+  }
+
+  function charge($item, $func=null, ?array $args=null, ?array &$values=null): int {
+    return $this->capacitor->charge($item, $func, $args, $values);
+  }
+
+  function discharge(bool $reset=true): iterable {
+    return $this->capacitor->discharge($reset);
+  }
+
+  function count($filter=null): int {
+    return $this->capacitor->count($filter);
+  }
+
+  function one($filter): ?array {
+    return $this->capacitor->one($filter);
+  }
+
+  function all($filter): iterable {
+    return $this->capacitor->all($filter);
+  }
+
+  function each($filter, $func=null, ?array $args=null, ?int &$updated=null): int {
+    return $this->capacitor->each($filter, $func, $args, $updated);
+  }
+
+  function delete($filter, $func=null, ?array $args=null): int {
+    return $this->capacitor->delete($filter, $func, $args);
+  }
 }
diff --git a/src/db/CapacitorStorage.php b/src/db/CapacitorStorage.php
index a204017..4448654 100644
--- a/src/db/CapacitorStorage.php
+++ b/src/db/CapacitorStorage.php
@@ -47,7 +47,21 @@ abstract class CapacitorStorage {
     }
     $definitions[] = $channel->getColumnDefinitions();
     $definitions[] = static::COLUMN_DEFINITIONS;
-    return cl::merge(...$definitions);
+    # forcer les définitions sans clé à la fin (sqlite requière par exemple que
+    # primary key (columns) soit à la fin)
+    $tmp = cl::merge(...$definitions);
+    $definitions = [];
+    $constraints = [];
+    $index = 0;
+    foreach ($tmp as $col => $def) {
+      if ($col === $index) {
+        $index++;
+        $constraints[] = $def;
+      } else {
+        $definitions[$col] = $def;
+      }
+    }
+    return cl::merge($definitions, $constraints);
   }
 
   /** sérialiser les valeurs qui doivent l'être dans $values */
@@ -284,7 +298,8 @@ EOT;
     # aucune modification
     if ($insert === null) return 0;
 
-    $manageTransactions = $channel->isManageTransactions();
+    # si on est déjà dans une transaction, désactiver la gestion des transactions
+    $manageTransactions = $channel->isManageTransactions() && !$db->inTransaction();
     if ($manageTransactions) {
       $commited = false;
       $db->beginTransaction();
@@ -474,15 +489,16 @@ EOT;
     func::ensure_func($func, $channel, $args);
     $onEach = func::_prepare($func);
     $db = $this->db();
-    $tableName = $channel->getTableName();
-    $manageTransactions = $channel->isManageTransactions();
-    $count = 0;
-    $updated = 0;
+    # si on est déjà dans une transaction, désactiver la gestion des transactions
+    $manageTransactions = $channel->isManageTransactions() && !$db->inTransaction();
     if ($manageTransactions) {
       $commited = false;
       $db->beginTransaction();
       $commitThreshold = $channel->getEachCommitThreshold();
     }
+    $count = 0;
+    $updated = 0;
+    $tableName = $channel->getTableName();
     try {
       $args ??= [];
       foreach ($this->_all($channel, $filter) as $values) {
@@ -541,14 +557,15 @@ EOT;
     func::ensure_func($func, $channel, $args);
     $onEach = func::_prepare($func);
     $db = $this->db();
-    $tableName = $channel->getTableName();
-    $manageTransactions = $channel->isManageTransactions();
-    $count = 0;
+    # si on est déjà dans une transaction, désactiver la gestion des transactions
+    $manageTransactions = $channel->isManageTransactions() && !$db->inTransaction();
     if ($manageTransactions) {
       $commited = false;
       $db->beginTransaction();
       $commitThreshold = $channel->getEachCommitThreshold();
     }
+    $count = 0;
+    $tableName = $channel->getTableName();
     try {
       $args ??= [];
       foreach ($this->_all($channel, $filter) as $values) {