From 97f312a1b536c92440b04ec3dd743fc2802ab150 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 13 Aug 2021 15:48:25 +0200
Subject: Optimize query_dependents() using prepared queries

---
 bpkg/database.hxx  |  1 +
 bpkg/odb.sh        |  5 +++--
 bpkg/package.cxx   | 45 ++++++++++++++++++++++++++++++++++++++++++---
 bpkg/package.hxx   |  6 ++++++
 bpkg/pkg-build.cxx |  6 +++---
 bpkg/pkg-drop.cxx  |  2 +-
 6 files changed, 56 insertions(+), 9 deletions(-)

diff --git a/bpkg/database.hxx b/bpkg/database.hxx
index 1961272..c7f059d 100644
--- a/bpkg/database.hxx
+++ b/bpkg/database.hxx
@@ -21,6 +21,7 @@
 namespace bpkg
 {
   using odb::query;
+  using odb::prepared_query;
   using odb::result;
   using odb::session;
 
diff --git a/bpkg/odb.sh b/bpkg/odb.sh
index 7f494e1..75c6d2d 100755
--- a/bpkg/odb.sh
+++ b/bpkg/odb.sh
@@ -50,6 +50,7 @@ $odb "${inc[@]}"                                                      \
     --hxx-prologue '#include <bpkg/pointer-traits.hxx>'               \
     --hxx-prologue '#include <bpkg/wrapper-traits.hxx>'               \
     --hxx-prologue '#include <bpkg/value-traits.hxx>'                 \
-    --include-with-brackets --include-prefix bpkg --guard-prefix BPKG \
-    --schema main --schema-version-table main.schema_version          \
+    --generate-prepared --include-with-brackets --include-prefix bpkg \
+    --guard-prefix BPKG --schema main                                 \
+    --schema-version-table main.schema_version                        \
     --sqlite-override-null package.hxx
diff --git a/bpkg/package.cxx b/bpkg/package.cxx
index 7995c34..8ad178d 100644
--- a/bpkg/package.cxx
+++ b/bpkg/package.cxx
@@ -684,10 +684,49 @@ namespace bpkg
                     const package_name& dep,
                     database& dep_db)
   {
+    // Prepare and cache this query since it's executed a lot. Note that we
+    // have to cache one per database.
+    //
     using query = query<package_dependent>;
+    using prep_query = prepared_query<package_dependent>;
+
+    struct params
+    {
+      string name;
+      string config;     // Configuration UUID.
+      string query_name;
+    };
+
+    params*    qp;
+    string     qn (db.uuid.string () + "-package-dependent-query");
+    prep_query pq (db.lookup_query<package_dependent> (qn.c_str (), qp));
+
+    if (!pq)
+    {
+      unique_ptr<params> p (qp = new params ());
+      p->query_name = move (qn);
+
+      query q ("prerequisite = " + query::_ref (p->name) + "AND" +
+               "configuration = " + query::_ref (p->config));
 
-    return db.query<package_dependent> (
-             "prerequisite = " + query::_val (dep.string ()) + "AND" +
-             "configuration = " + query::_val (dep_db.uuid.string ()));
+      pq = db.prepare_query<package_dependent> (p->query_name.c_str (), q);
+      db.cache_query (pq, move (p));
+    }
+
+    qp->name   = dep.string ();
+    qp->config = dep_db.uuid.string ();
+
+    return pq.execute ();
+  }
+
+  vector<package_dependent>
+  query_dependents_cache (database& db,
+                          const package_name& dep,
+                          database& dep_db)
+  {
+    vector<package_dependent> r;
+    for (package_dependent& pd: query_dependents (db, dep, dep_db))
+      r.push_back (move (pd));
+    return r;
   }
 }
diff --git a/bpkg/package.hxx b/bpkg/package.hxx
index a0e809a..1a62cd9 100644
--- a/bpkg/package.hxx
+++ b/bpkg/package.hxx
@@ -1314,6 +1314,12 @@ namespace bpkg
                     const package_name& dependency,
                     database& dependency_db);
 
+  // As above but cache the result in a vector. This version should be used if
+  // query_dependents*() may be called recursively.
+  //
+  vector<package_dependent>
+  query_dependents_cache (database&, const package_name&, database&);
+
   // Database and package name pair.
   //
   // It is normally used as a key for maps containing data for packages across
diff --git a/bpkg/pkg-build.cxx b/bpkg/pkg-build.cxx
index d8e5cda..1e8e9dd 100644
--- a/bpkg/pkg-build.cxx
+++ b/bpkg/pkg-build.cxx
@@ -1839,7 +1839,7 @@ namespace bpkg
 
       for (database& ddb: pdb.dependent_configs ())
       {
-        for (auto& pd: query_dependents (ddb, n, pdb))
+        for (auto& pd: query_dependents_cache (ddb, n, pdb))
         {
           package_name& dn (pd.name);
           auto i (map_.find (ddb, dn));
@@ -2938,7 +2938,7 @@ namespace bpkg
 
     for (database& ddb: db.dependent_configs ())
     {
-      for (auto& pd: query_dependents (ddb, nm, db))
+      for (auto& pd: query_dependents_cache (ddb, nm, db))
       {
         // Note that we cannot end up with an infinite recursion for
         // configured packages due to a dependency cycle (see order() for
@@ -2998,7 +2998,7 @@ namespace bpkg
 
     for (database& ddb: db.dependent_configs ())
     {
-      for (auto& pd: query_dependents (ddb, sp->name, db))
+      for (auto& pd: query_dependents_cache (ddb, sp->name, db))
       {
         shared_ptr<selected_package> dsp (
           ddb.load<selected_package> (pd.name));
diff --git a/bpkg/pkg-drop.cxx b/bpkg/pkg-drop.cxx
index e060e96..dfae66f 100644
--- a/bpkg/pkg-drop.cxx
+++ b/bpkg/pkg-drop.cxx
@@ -110,7 +110,7 @@ namespace bpkg
     {
       for (database& ddb: db.dependent_configs ())
       {
-        for (auto& pd: query_dependents (ddb, p->name, db))
+        for (auto& pd: query_dependents_cache (ddb, p->name, db))
         {
           const package_name& dn (pd.name);
 
-- 
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