finish rudimenary pluggable merchant postgres backend

2 files changed, 135 insertions, 503 deletions

diff --git a/src/backenddb/plugin_merchantdb_postgres.c b/src/backenddb/plugin_merchantdb_postgres.c
index 02e6884b..f8502773 100644
--- a/src/backenddb/plugin_merchantdb_postgres.c
+++ b/src/backenddb/plugin_merchantdb_postgres.c
@@ -13,10 +13,9 @@
   You should have received a copy of the GNU General Public License along with
   TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
 */
-
 /**
- * @file merchant/merchant_db.c
- * @brief database helper functions used by the merchant
+ * @file merchant/plugin_merchantdb_postgres.c
+ * @brief database helper functions for postgres used by the merchant
  * @author Sree Harsha Totakura <sreeharsha@totakura.in>
  */
 #include "platform.h"
@@ -26,14 +25,25 @@
 #include <taler/taler_pq_lib.h>
 #include "taler_merchantdb_plugin.h"
 
+
 /**
- * Shorthand for exit jumps.
+ * Type of the "cls" argument given to each of the functions in
+ * our API.
  */
-#define EXITIF(cond)                                              \
-  do {                                                            \
-    if (cond) { GNUNET_break (0); goto EXITIF_exit; }             \
-  } while (0)
+struct PostgresClosure
+{
 
+  /**
+   * Postgres connection handle.
+   */
+  PGconn *conn;
+
+  /**
+   * Database connection string, as read from
+   * the configuration.
+   */
+  char *connection_cfg_str;
+};
 
 
 #define PQSQL_strerror(kind, cmd, res)                \
@@ -41,397 +51,117 @@
                    "SQL %s failed at %s:%u with error: %s", \
                    cmd, __FILE__, __LINE__, PQresultErrorMessage (res));
 
-/**
- * Shorthand for exit jumps.
- */
-#define EXITIF(cond)                                              \
-  do {                                                            \
-    if (cond) { GNUNET_break (0); goto EXITIF_exit; }             \
-  } while (0)
-
-
-/**
- * Connect to postgresql database
- *
- * @param cfg the configuration handle
- * @return connection to the postgresql database; NULL upon error
- */
-PGconn *
-TALER_MERCHANTDB_connect (const struct GNUNET_CONFIGURATION_Handle *cfg)
-{
-  return GNUNET_POSTGRES_connect (cfg, "merchant-db");
-}
-
-
-/**
- * Disconnect from the database
- *
- * @param conn database handle to close
- */
-void
-TALER_MERCHANTDB_disconnect (PGconn *conn)
-{
-  PQfinish (conn);
-}
-
 
 /**
  * Initialize merchant tables
  *
- * @param conn the connection handle to postgres db.
- * @param tmp GNUNET_YES if the tables are to be made temporary i.e. their
- *          contents are dropped when the @a conn is closed
- * @return GNUNET_OK upon success; GNUNET_SYSERR upon failure
+ * @param cls closure our `struct Plugin`
+ * @param tmp #GNUNET_YES if the tables are to be made temporary i.e. their
+ *          contents are dropped when the database connection is closed
+ * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
  */
-int
-TALER_MERCHANTDB_initialize (PGconn *conn, int tmp)
+static int
+postgres_initialize (void *cls,
+                     int tmp)
 {
+  struct PostgresClosure *pg = cls;
   const char *tmp_str = (1 == tmp) ? "TEMPORARY" : "";
   char *sql;
   PGresult *res;
   ExecStatusType status;
   int ret;
 
-  res = NULL;
-  (void) GNUNET_asprintf (&sql,
-                          "BEGIN TRANSACTION;"
-                          "CREATE %1$s TABLE IF NOT EXISTS contracts ("
-                          "contract_id INT8 PRIMARY KEY,"
-			  "hash BYTEA NOT NULL,"
-                          "amount INT8 NOT NULL,"
-                          "amount_fraction INT4 NOT NULL,"
-			  "amount_currency VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL,"
-                          "description TEXT NOT NULL,"
-                          "nounce INT8 NOT NULL,"
-                          "timestamp INT8 NOT NULL,"
-                          "expiry INT8 NOT NULL,"
-                          "edate INT8 NOT NULL,"
-                          "refund_deadline INT8 NOT NULL,"
-                          "product INT8 NOT NULL);"
-                          "CREATE %1$s TABLE IF NOT EXISTS checkouts ("
-                          "coin_pub BYTEA PRIMARY KEY,"
-                          "contract_id INT8 REFERENCES contracts(contract_id),"
-                          "amount INT4 NOT NULL,"
-                          "amount_fraction INT4 NOT NULL,"
-                          "coin_sig BYTEA NOT NULL);"
-			  "CREATE %1$s TABLE IF NOT EXISTS deposits ("
-			  "dep_perm VARCHAR NOT NULL,"
-			  "transaction_id INT8,"
-			  "pending INT4 NOT NULL,"
-			  "mint_url VARCHAR NOT NULL);",
-                          tmp_str);
-  ret = GNUNET_POSTGRES_exec (conn, sql);
-  (void) GNUNET_POSTGRES_exec (conn,
-                              (GNUNET_OK == ret) ? "COMMIT;" : "ROLLBACK;");
+  GNUNET_asprintf (&sql,
+                   "CREATE %1$s TABLE IF NOT EXISTS payments ("
+                   "h_contract BYTEA NOT NULL,"
+                   "h_wire BYTEA NOT NULL,"
+                   "transaction_id INT8 PRIMARY KEY,"
+                   "timestamp INT8 NOT NULL,"
+                   "refund_deadline INT8 NOT NULL,"
+                   "amount_without_fee_val INT8 NOT NULL,"
+                   "amount_without_fee_frac INT4 NOT NULL,"
+                   "amount_without_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL,"
+                   "coin_pub BYTEA NOT NULL,"
+                   "mint_sig BYTEA NOT NULL);",
+                   tmp_str);
+  ret = GNUNET_POSTGRES_exec (pg->conn,
+                              sql);
   GNUNET_free (sql);
   if (GNUNET_OK != ret)
     return ret;
-
-  while (NULL != (res = PQgetResult (conn)))
-  {
-    status = PQresultStatus (res);
-    PQclear (res);
-  }
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "contract_create",
-                    "INSERT INTO contracts"
-                    "(contract_id, hash, timestamp, expiry, edate,"
-		    "refund_deadline, amount, amount_fraction, amount_currency,"
-		    "description, nounce, product) VALUES"
-                    "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12)",
-                    12, NULL)));
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
-  PQclear (res);
-
-
-  /* Query aimed to get the contract's nounce and edate which will be
-  both used for regenerating a 'wire' JSON object to insert into the
-  deposit permission. Implicitly, this query will tell whether a contract
-  was created or not */
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "get_contract_hash",
-                    "SELECT "
-                    "nounce, edate "
-                    "FROM contracts "
-                    "WHERE ("
-                    "hash=$1"
-                    ")",
-                    1, NULL)));
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
-  PQclear (res);
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "get_contract_set",
-                    "SELECT "
-                    "contract_id, nounce, timestamp, edate, "
-                    "refund_deadline FROM contracts "
-                    "WHERE ("
-                    "hash=$1"
-                    ")",
-                    1, NULL)));
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
-  PQclear (res);
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "store_deposit_permission",
-                    "INSERT INTO deposits"
-                    "(dep_perm, transaction_id, pending, mint_url) "
-                    "VALUES ($1, $2, $3, $4);", 4, NULL)));
-
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
-  PQclear (res);
-
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "update_deposit_permission",
-                    "UPDATE deposits "
-                    "SET pending = $1 "
-                    "WHERE transaction_id = $2", 2, NULL)));
-
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
-  PQclear (res);
-
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "get_contract_product",
-                    "SELECT ("
-                    "product"
-                    ") FROM contracts "
-                    "WHERE ("
-                    "contract_id=$1"
-                    ")",
-                    1, NULL)));
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus(res)));
-  PQclear (res);
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "checkout_create",
-                    "INSERT INTO checkouts ("
-                    "coin_pub,"
-                    "contract_id,"
-                    "amount,"
-                    "amount_fraction,"
-                    "coin_sig"
-                    ") VALUES ("
-                    "$1, $2, $3, $4, $5"
-                    ")",
-                    5, NULL)));
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus (res)));
-  PQclear (res);
-
-  EXITIF (NULL == (res = PQprepare
-                   (conn,
-                    "get_checkout_product",
-                    "SELECT ("
-                    "product"
-                    ") FROM contracts "
-                    "WHERE "
-                    "contract_id IN ("
-                    "SELECT (contract_id) FROM checkouts "
-                    "WHERE coin_pub=$1"
-                    ")",
-                    1, NULL)));
-  EXITIF (PGRES_COMMAND_OK != (status = PQresultStatus (res)));
-  PQclear (res);
-
-  return GNUNET_OK;
-
- EXITIF_exit:
-  if (NULL != res)
-  {
-    PQSQL_strerror (GNUNET_ERROR_TYPE_ERROR, "PQprepare", res);
-    PQclear (res);
-  }
-  return GNUNET_SYSERR;
-}
-
-
-/**
- * Update the pending column of a deposit permission
- * @param conn handle to DB
- * @param transaction_id identification number of the deposit to
- * update
- * @param pending true if still pending, false otherwise (i.e. the
- * mint did respond something)
- * @return #GNUNET_OK if successful, #GNUNET_SYSERR upon errors
- */
-uint32_t
-TALER_MERCHANTDB_deposit_permission_update (PGconn *conn,
-                                       uint64_t transaction_id,
-				       unsigned int pending)
-{
-  PGresult *res;
-  ExecStatusType status;
-
-  struct TALER_PQ_QueryParam params[] = {
-    TALER_PQ_query_param_uint32 (&pending),
-    TALER_PQ_query_param_uint64 (&transaction_id),
-    TALER_PQ_query_param_end
-  };
-
-  res = TALER_PQ_exec_prepared (conn, "update_deposit_permission", params);
-  status = PQresultStatus (res);
-
-  if (PGRES_COMMAND_OK != status)
+  if ( (NULL == (res = PQprepare (pg->conn,
+                                  "insert_payment",
+                                  "INSERT INTO payments"
+                                  "(h_contract"
+                                  ",h_wire"
+                                  ",transaction_id"
+                                  ",timestamp"
+                                  ",refund_deadline"
+                                  ",amount_without_fee_val"
+                                  ",amount_without_fee_frac"
+                                  ",amount_without_fee_curr"
+                                  ",coin_pub"
+                                  ",mint_sig) VALUES "
+                                  "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)",
+                                  10, NULL))) ||
+       (PGRES_COMMAND_OK != (status = PQresultStatus(res))) )
   {
-
-    const char *sqlstate;
-
-    sqlstate = PQresultErrorField (res, PG_DIAG_SQLSTATE);
-    if (NULL == sqlstate)
+    if (NULL != res)
     {
-      /* very unexpected... */
-      GNUNET_break (0);
+      PQSQL_strerror (GNUNET_ERROR_TYPE_ERROR, "PQprepare", res);
       PQclear (res);
-      return GNUNET_SYSERR;
     }
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Database commit failure: %s\n",
-                sqlstate);
-    PQclear (res);
     return GNUNET_SYSERR;
   }
+  PQclear (res);
   return GNUNET_OK;
 }
 
 
 /**
- * Store a deposit permission in DB. To be mainly used if /deposit should
- * be retried; also, the merchant can benefit from this information in case
- * he needs to later investigate about some @a transaction_id.
- *
- * @param conn DB handle
- * @param transaction_id identification number of this payment (which is the
- * same id of the related contract)
- * @param pending if true, this payment got to a persistent state
- * @param which mint is to get this deposit permission
- * @return #GNUNET_OK if successful, #GNUNET_SYSERR upon errors
- */
-uint32_t
-TALER_MERCHANTDB_deposit_permission_store (PGconn *conn,
-                                      const char *deposit_permission,
-				      uint64_t transaction_id,
-				      unsigned int pending,
-				      const char *mint_url)
-{
-  PGresult *res;
-  ExecStatusType status;
-  struct TALER_PQ_QueryParam params[] = {
-    TALER_PQ_query_param_fixed_size (deposit_permission, strlen (deposit_permission)),
-    TALER_PQ_query_param_uint64 (&transaction_id),
-    TALER_PQ_query_param_uint32 (&pending),
-    TALER_PQ_query_param_fixed_size (mint_url, strlen (mint_url)),
-    TALER_PQ_query_param_end
-  };
-
-  res = TALER_PQ_exec_prepared (conn, "store_deposit_permission", params);
-  status = PQresultStatus (res);
-
-  if (PGRES_COMMAND_OK != status)
-  {
-    const char *sqlstate;
-
-    sqlstate = PQresultErrorField (res, PG_DIAG_SQLSTATE);
-    if (NULL == sqlstate)
-    {
-      /* very unexpected... */
-      GNUNET_break (0);
-      PQclear (res);
-      return GNUNET_SYSERR;
-    }
-    /* 40P01: deadlock, 40001: serialization failure */
-    if ( (0 == strcmp (sqlstate,
-                       "23505")))
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-		  "Inserting same transaction id twice\n");
-      /* Primary key violation */
-      PQclear (res);
-      return GNUNET_SYSERR;
-    }
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Database commit failure: %s\n",
-                sqlstate);
-    PQclear (res);
-    return GNUNET_SYSERR;
-  }
-
-    PQclear (res);
-    return GNUNET_OK;
-}
-
-
-/**
- * Insert a contract record into the database and if successfull
- * return the serial number of the inserted row.
+ * Insert payment confirmation from the mint into the database.
  *
- * @param conn the database connection
- * @param timestamp the timestamp of this contract
- * @param expiry the time when the contract will expire
- * @param edate when the merchant wants to receive the wire transfer
- * corresponding to this deal (this value is also a field inside the
- * 'wire' JSON format)
- * @param refund deadline until which the merchant can return the paid
- * amount
- * @param amount the taler amount corresponding to the contract
- * @param hash of the stringified JSON corresponding to this contract
- * @param c_id contract's id
- * @param desc descripition of the contract
- * @param nounce a random 64-bit nounce
- * @param product description to identify a product
- * @return #GNUNET_OK on success, #GNUNET_NO if attempting to insert an
- * already inserted @a c_id, #GNUNET_SYSERR for other errors.
+ * @param cls our plugin handle
+ * @param h_contract hash of the contract
+ * @param h_wire hash of our wire details
+ * @param transaction_id of the contract
+ * @param timestamp time of the confirmation
+ * @param refund refund deadline
+ * @param amount_without_fee amount the mint will deposit
+ * @param coin_pub public key of the coin
+ * @param merchant_pub our public key
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR upon error
  */
-uint32_t
-TALER_MERCHANTDB_contract_create (PGconn *conn,
-                             const struct GNUNET_TIME_Absolute timestamp,
-                             const struct GNUNET_TIME_Absolute expiry,
-			     struct GNUNET_TIME_Absolute edate,
-			     struct GNUNET_TIME_Absolute refund,
-                             const struct TALER_Amount *amount,
-			     const struct GNUNET_HashCode *h_contract,
-			     uint64_t c_id,
-                             const char *desc,
-                             uint64_t nounce,
-                             uint64_t product)
+static int
+postgres_store_payment (void *cls,
+                        const struct GNUNET_HashCode *h_contract,
+                        const struct GNUNET_HashCode *h_wire,
+                        uint64_t transaction_id,
+                        struct GNUNET_TIME_Absolute timestamp,
+                        struct GNUNET_TIME_Absolute refund,
+                        const struct TALER_Amount *amount_without_fee,
+                        const struct TALER_CoinSpendPublicKeyP *coin_pub,
+                        const struct TALER_MintSignatureP *mint_sig)
 {
+  struct PostgresClosure *pg = cls;
   PGresult *res;
-#if 0
-  uint64_t expiry_ms_nbo;
-  uint64_t value_nbo;
-  uint32_t fraction_nbo;
-  uint64_t nounce_nbo;
-#endif
   ExecStatusType status;
 
   struct TALER_PQ_QueryParam params[] = {
-    TALER_PQ_query_param_uint64 (&c_id),
-    TALER_PQ_query_param_fixed_size (h_contract, sizeof (struct GNUNET_HashCode)),
+    TALER_PQ_query_param_auto_from_type (h_contract),
+    TALER_PQ_query_param_auto_from_type (h_wire),
+    TALER_PQ_query_param_uint64 (&transaction_id),
     TALER_PQ_query_param_absolute_time (&timestamp),
-    TALER_PQ_query_param_absolute_time (&expiry),
-    TALER_PQ_query_param_absolute_time (&edate),
     TALER_PQ_query_param_absolute_time (&refund),
-    TALER_PQ_query_param_amount (amount),
-    /* A *string* is being put in the following statement,
-    though the column is declared as *blob*. Will this be
-    liked by the DB ? */
-    TALER_PQ_query_param_fixed_size (desc, strlen (desc)),
-    TALER_PQ_query_param_uint64 (&nounce),
-    TALER_PQ_query_param_uint64 (&product),
+    TALER_PQ_query_param_amount (amount_without_fee),
+    TALER_PQ_query_param_auto_from_type (coin_pub),
+    TALER_PQ_query_param_auto_from_type (mint_sig),
     TALER_PQ_query_param_end
   };
 
-  /* NOTE: the statement is prepared by TALER_MERCHANTDB_initialize function */
-  res = TALER_PQ_exec_prepared (conn, "contract_create", params);
+  res = TALER_PQ_exec_prepared (pg->conn,
+                                "insert_payment",
+                                params);
   status = PQresultStatus (res);
 
   if (PGRES_COMMAND_OK != status)
@@ -466,154 +196,56 @@ TALER_MERCHANTDB_contract_create (PGconn *conn,
 }
 
 
-long long
-TALER_MERCHANTDB_contract_get_product (PGconn *conn,
-                                  uint64_t contract_id)
-{
-  PGresult *res;
-  uint64_t product;
-  ExecStatusType status;
-  struct TALER_PQ_QueryParam params[] = {
-    TALER_PQ_query_param_uint64 (&contract_id),
-    TALER_PQ_query_param_end
-  };
-  struct TALER_PQ_ResultSpec rs[] = {
-    TALER_PQ_result_spec_uint64 ("product", &product),
-    TALER_PQ_result_spec_end
-  };
-
-  contract_id = GNUNET_htonll (contract_id);
-  res = TALER_PQ_exec_prepared (conn, "get_contract_product", params);
-  status = PQresultStatus (res);
-  EXITIF (PGRES_TUPLES_OK != status);
-  EXITIF (1 != PQntuples (res));
-  EXITIF (GNUNET_YES != TALER_PQ_extract_result (res, rs, 0));
-  PQclear (res);
-  return GNUNET_ntohll ((uint64_t) product);
-
- EXITIF_exit:
-  PQclear (res);
-  return -1;
-}
-
-
-unsigned int
-TALER_MERCHANTDB_checkout_create (PGconn *conn,
-                             struct GNUNET_CRYPTO_rsa_PublicKey *coin_pub,
-                             uint64_t transaction_id,
-                             struct TALER_Amount *amount,
-                             struct GNUNET_CRYPTO_rsa_Signature *coin_sig)
-{
-  PGresult *res;
-  ExecStatusType status;
-  uint32_t value_nbo;
-  uint32_t fraction_nbo;
-  struct TALER_PQ_QueryParam params[] = {
-    TALER_PQ_query_param_rsa_public_key (coin_pub),
-    TALER_PQ_query_param_uint64 (&transaction_id),
-    TALER_PQ_query_param_uint32 (&value_nbo),
-    TALER_PQ_query_param_uint32 (&fraction_nbo),
-    TALER_PQ_query_param_rsa_signature (coin_sig),
-    TALER_PQ_query_param_end
-  };
-
-  transaction_id = GNUNET_htonll (transaction_id);
-  value_nbo = htonl (amount->value);
-  fraction_nbo = htonl (amount->fraction);
-  res = TALER_PQ_exec_prepared (conn, "checkout_create", params);
-  status = PQresultStatus (res);
-  EXITIF (PGRES_COMMAND_OK != status);
-  PQclear (res);
-  return GNUNET_OK;
-
- EXITIF_exit:
-  PQclear (res);
-  return GNUNET_SYSERR;
-}
-
-
-long long
-TALER_MERCHANTDB_checkout_get_product (PGconn *conn,
-                                  struct GNUNET_CRYPTO_rsa_PublicKey *coin_pub)
+/**
+ * Initialize Postgres database subsystem.
+ *
+ * @param cls a configuration instance
+ * @return NULL on error, otherwise a `struct TALER_MERCHANTDB_Plugin`
+ */
+void *
+libtaler_plugin_merchantdb_postgres_init (void *cls)
 {
-  PGresult *res;
-  ExecStatusType status;
-  uint64_t product;
-  struct TALER_PQ_QueryParam params[] = {
-    TALER_PQ_query_param_rsa_public_key (coin_pub),
-    TALER_PQ_query_param_end
-  };
-  struct TALER_PQ_ResultSpec rs[] = {
-    TALER_PQ_result_spec_uint64 ("product", &product),
-    TALER_PQ_result_spec_end
-  };
-
-  product = -1;
-  res = TALER_PQ_exec_prepared (conn, "get_checkout_product", params);
-  status = PQresultStatus (res);
-  EXITIF (PGRES_TUPLES_OK != status);
-  if (0 == PQntuples (res))
+  struct GNUNET_CONFIGURATION_Handle *cfg = cls;
+  struct PostgresClosure *pg;
+  struct TALER_MERCHANTDB_Plugin *plugin;
+
+  pg = GNUNET_new (struct PostgresClosure);
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_string (cfg,
+                                             "merchantdb-postgres",
+                                             "db_conn_str",
+                                             &pg->connection_cfg_str))
   {
-    TALER_LOG_DEBUG ("Checkout not found for given coin");
-    goto EXITIF_exit;
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "merchant",
+                               "db_conn_str");
+    return NULL;
   }
-  EXITIF (1 != PQntuples (res));
-  EXITIF (GNUNET_YES != TALER_PQ_extract_result (res, rs, 0));
-  PQclear (res);
-  return GNUNET_ntohll ((uint64_t) product);
+  pg->conn = GNUNET_POSTGRES_connect (cfg, "merchant-db");
+  plugin = GNUNET_new (struct TALER_MERCHANTDB_Plugin);
+  plugin->cls = pg;
+  plugin->initialize = &postgres_initialize;
+  plugin->store_payment = &postgres_store_payment;
 
- EXITIF_exit:
-  PQclear (res);
-  return -1;
+  return plugin;
 }
 
 
 /**
- * The query gets a contract's nounce and edate used to reproduce
- * a 'wire' JSON object. This function is also useful to check whether
- * a claimed contract existed or not.
+ * Shutdown Postgres database subsystem.
  *
- * @param conn handle to the DB
- * @param h_contract the parameter for the row to match against
- * @param nounce where to store the found nounce
- * @param edate where to store the found edate
- * @return #GNUNET_OK on success, #GNUNET_SYSERR upon errors
+ * @param cls a `struct TALER_MERCHANTDB_Plugin`
+ * @return NULL (always)
  */
-uint32_t
-TALER_MERCHANTDB_contract_get_values (PGconn *conn,
-                                 const struct GNUNET_HashCode *h_contract,
-                                 uint64_t *nounce,
-				 struct GNUNET_TIME_Absolute *edate)
+void *
+libtaler_plugin_merchantdb_postgres_done (void *cls)
 {
-  PGresult *res;
-  ExecStatusType status;
-
-  struct TALER_PQ_QueryParam params[] = {
-      TALER_PQ_query_param_fixed_size (h_contract, sizeof (struct GNUNET_HashCode)),
-      TALER_PQ_query_param_end
-  };
-  struct TALER_PQ_ResultSpec rs[] = {
-   TALER_PQ_result_spec_uint64 ("nounce", nounce),
-   TALER_PQ_result_spec_absolute_time ("edate", edate),
-   TALER_PQ_result_spec_end
-  };
-
-  res = TALER_PQ_exec_prepared (conn, "get_contract_hash", params);
-
-  status = PQresultStatus (res);
-  EXITIF (PGRES_TUPLES_OK != status);
-  if (0 == PQntuples (res))
-  {
-    TALER_LOG_DEBUG ("Contract not found");
-    goto EXITIF_exit;
-  }
-
-  EXITIF (1 != PQntuples (res));
-  EXITIF (GNUNET_YES != TALER_PQ_extract_result (res, rs, 0));
-  PQclear (res);
-  return GNUNET_OK;
-
-  EXITIF_exit:
-  PQclear (res);
-  return GNUNET_SYSERR;
+  struct TALER_MERCHANTDB_Plugin *plugin = cls;
+  struct PostgresClosure *pg = plugin->cls;
+
+  GNUNET_free (pg->connection_cfg_str);
+  PQfinish (pg->conn);
+  GNUNET_free (pg);
+  GNUNET_free (plugin);
+  return NULL;
 }
diff --git a/src/include/taler_merchantdb_plugin.h b/src/include/taler_merchantdb_plugin.h
index 9350ccb9..b6e378c6 100644
--- a/src/include/taler_merchantdb_plugin.h
+++ b/src/include/taler_merchantdb_plugin.h
@@ -49,7 +49,7 @@ struct TALER_MERCHANTDB_Plugin
   /**
    * Initialize merchant tables
    *
-   * @param conn the connection handle to postgres db.
+   * @param cls closure
    * @param tmp #GNUNET_YES if the tables are to be made temporary i.e. their
    *          contents are dropped when the @a conn is closed
    * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
@@ -59,9 +59,9 @@ struct TALER_MERCHANTDB_Plugin
                  int tmp);
 
   /**
-   * Inserts a contract record into the database.
+   * Insert payment confirmation from the mint into the database.
    *
-   * @param dbh the database connection
+   * @param cls closure
    * @param h_contract hash of the contract
    * @param h_wire hash of our wire details
    * @param transaction_id of the contract