From fb952babf67c41dedf3fac6b9d89eccf7fc10b2e Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Fri, 19 Oct 2018 11:01:40 +0200
Subject: reduce redundant data fetch (#5444)

---
 src/exchangedb/plugin_exchangedb_postgres.c | 42 +++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

(limited to 'src/exchangedb/plugin_exchangedb_postgres.c')

diff --git a/src/exchangedb/plugin_exchangedb_postgres.c b/src/exchangedb/plugin_exchangedb_postgres.c
index 7da15ced3..b2731366a 100644
--- a/src/exchangedb/plugin_exchangedb_postgres.c
+++ b/src/exchangedb/plugin_exchangedb_postgres.c
@@ -858,6 +858,14 @@ postgres_prepare (PGconn *db_conn)
                             "     ON (kc.denom_pub_hash = denom.denom_pub_hash)"
                             " WHERE rc=$1;",
                             1),
+    /* Used in #postgres_get_melt_index() to fetch
+       the noreveal index from a previous melt operation */
+    GNUNET_PQ_make_prepare ("get_melt_index",
+                            "SELECT"
+                            " noreveal_index"
+                            " FROM refresh_commitments"
+                            " WHERE rc=$1;",
+                            1),
     /* Used in #postgres_select_refreshs_above_serial_id() to fetch
        refresh session with id '\geq' the given parameter */
     GNUNET_PQ_make_prepare ("audit_get_refresh_commitments_incr",
@@ -3484,6 +3492,39 @@ postgres_get_melt (void *cls,
 }
 
 
+/**
+ * Lookup noreveal index of a previous melt operation under the given
+ * @a rc.
+ *
+ * @param cls the `struct PostgresClosure` with the plugin-specific state
+ * @param session database handle to use
+ * @param rc commitment hash to use to locate the operation
+ * @param[out] refresh_melt where to store the result
+ * @return transaction status
+ */
+static enum GNUNET_DB_QueryStatus
+postgres_get_melt_index (void *cls,
+                         struct TALER_EXCHANGEDB_Session *session,
+                         const struct TALER_RefreshCommitmentP *rc,
+                         uint32_t *noreveal_index)
+{
+  struct GNUNET_PQ_QueryParam params[] = {
+    GNUNET_PQ_query_param_auto_from_type (rc),
+    GNUNET_PQ_query_param_end
+  };
+  struct GNUNET_PQ_ResultSpec rs[] = {
+    GNUNET_PQ_result_spec_uint32 ("noreveal_index",
+				  noreveal_index),
+    GNUNET_PQ_result_spec_end
+  };
+
+  return GNUNET_PQ_eval_prepared_singleton_select (session->conn,
+                                                   "get_melt_index",
+                                                   params,
+                                                   rs);
+}
+
+
 /**
  * Store new refresh melt commitment data.
  *
@@ -7035,6 +7076,7 @@ libtaler_plugin_exchangedb_postgres_init (void *cls)
   plugin->select_refunds_by_coin = &postgres_select_refunds_by_coin;
   plugin->insert_melt = &postgres_insert_melt;
   plugin->get_melt = &postgres_get_melt;
+  plugin->get_melt_index = &postgres_get_melt_index;
   plugin->insert_refresh_reveal = &postgres_insert_refresh_reveal;
   plugin->get_refresh_reveal = &postgres_get_refresh_reveal;
   plugin->get_link_data = &postgres_get_link_data;
-- 
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