Add support for HTTP patch and application of patch scripts to server and data store components.

git-svn-id: http://svn.us.apache.org/repos/asf/tuscany@1428192 13f79535-47bb-0310-9956-ffa450edef68

21 files changed, 591 insertions, 39 deletions

diff --git a/sca-cpp/trunk/components/cache/client-test.cpp b/sca-cpp/trunk/components/cache/client-test.cpp
index 5e9be6c14a..3c8a261f84 100644
--- a/sca-cpp/trunk/components/cache/client-test.cpp
+++ b/sca-cpp/trunk/components/cache/client-test.cpp
@@ -81,6 +81,32 @@ const bool testCache(const string& uri) {
         assert(hasContent(val));
         assert(content(val) == b);
     }
+
+    const list<value> k = nilListValue + "content" + (nilListValue + "item" 
+            + (nilListValue + "name" + string("Apple"))
+            + (nilListValue + "price" + string("$3.99")));
+    const list<value> c = nilListValue + (nilListValue + "entry" 
+            + (nilListValue + "title" + string("item"))
+            + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+            + k);
+
+    {
+        const list<value> s = nilListValue + "content" +
+            (nilListValue + "patch" + string("(define (patch id e) (tree-subst-assoc '(price) '(price \"$3.99\") e))"));
+        const list<value> ps = nilListValue + (nilListValue + "entry" 
+                + (nilListValue + "title" + string("item"))
+                + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+                + s);
+
+        const failable<value> r = http::patch(ps, uri + p, cs);
+        assert(hasContent(r));
+        assert(content(r) == trueValue);
+    }
+    {
+        const failable<value> val = http::get(uri + p, cs);
+        assert(hasContent(val));
+        assert(content(val) == c);
+    }
     {
         const failable<value> r = http::del(uri + p, cs);
         assert(hasContent(r));
diff --git a/sca-cpp/trunk/components/cache/datacache.cpp b/sca-cpp/trunk/components/cache/datacache.cpp
index 975ca43dce..4fafd9e345 100644
--- a/sca-cpp/trunk/components/cache/datacache.cpp
+++ b/sca-cpp/trunk/components/cache/datacache.cpp
@@ -95,6 +95,20 @@ const failable<value> put(const value& key, const value& val, unused const lvvla
 }
 
 /**
+ * Patch an item in the cache.
+ */
+const failable<value> patch(const value& key, const value& val, unused const lvvlambda& rcache1, const lvvlambda& wcache1, unused const lvvlambda& rcache2, const lvvlambda& wcache2) {
+
+    // Update level1 cache
+    wcache1(mklist<value>("patch", key, val));
+
+    // Update level2 cache
+    wcache2(mklist<value>("patch", key, val));
+
+    return trueValue;
+}
+
+/**
  * Delete an item from the cache.
  */
 const failable<value> del(const value& key, unused const lvvlambda& rcache1, const lvvlambda& wcache1, unused const lvvlambda& rcache2, const lvvlambda& wcache2) {
@@ -121,6 +135,8 @@ const tuscany::value apply(const tuscany::list<tuscany::value>& params) {
         return tuscany::datacache::post(cadr(params), caddr(params), cadddr(params), caddddr(params), cadddddr(params), caddddddr(params));
     if (func == "put")
         return tuscany::datacache::put(cadr(params), caddr(params), cadddr(params), caddddr(params), cadddddr(params), caddddddr(params));
+    if (func == "patch")
+        return tuscany::datacache::patch(cadr(params), caddr(params), cadddr(params), caddddr(params), cadddddr(params), caddddddr(params));
     if (func == "delete")
         return tuscany::datacache::del(cadr(params), caddr(params), cadddr(params), caddddr(params), cadddddr(params));
     return tuscany::mkfailure<tuscany::value>();
diff --git a/sca-cpp/trunk/components/cache/memcache-test.cpp b/sca-cpp/trunk/components/cache/memcache-test.cpp
index 6c6adb0541..10eda45eae 100644
--- a/sca-cpp/trunk/components/cache/memcache-test.cpp
+++ b/sca-cpp/trunk/components/cache/memcache-test.cpp
@@ -40,6 +40,8 @@ bool testMemCached() {
     assert(get(k, ch) == value(string("AAA")));
     assert(hasContent(put(k, string("aaa"), ch)));
     assert(get(k, ch) == value(string("aaa")));
+    assert(hasContent(patch(k, string("bbb"), ch)));
+    assert(get(k, ch) == value(string("bbb")));
     assert(hasContent(del(k, ch)));
     assert(!hasContent(get(k, ch)));
 
diff --git a/sca-cpp/trunk/components/cache/memcache.cpp b/sca-cpp/trunk/components/cache/memcache.cpp
index 2e4597efd3..e1a3c7e9af 100644
--- a/sca-cpp/trunk/components/cache/memcache.cpp
+++ b/sca-cpp/trunk/components/cache/memcache.cpp
@@ -63,6 +63,39 @@ const failable<value> put(const list<value>& params, const memcache::MemCached&
 }
 
 /**
+ * Patch an item in the cache.
+ */
+const failable<value> patch(const list<value>& params, const memcache::MemCached& ch) {
+    // Read patch
+    value p = assoc<value>("patch", assoc<value>("content", car<value>(cadr(params))));
+    if (isNil(p))
+        return mkfailure<value>("Couldn't read patch script");
+    const string script = cadr<value>(p);
+    debug(script, "memcache::patch::script");
+    istringstream is(script);
+
+    // Get existing value from cache
+    const failable<value> ival = memcache::get(car(params), ch);
+    if (!hasContent(ival) && rcode(ival) != 404)
+        return mkfailure<value>(ival);
+
+    // Apply patch
+    scheme::Env env = scheme::setupEnvironment();
+    const value pval = scheme::evalScript(cons<value>("patch", scheme::quotedParameters(mklist<value>(car(params), hasContent(ival)? content(ival) : (value)list<value>()))), is, env);
+    if (isNil(pval)) {
+        ostringstream os;
+        os << "Couldn't patch memcached entry: " << car(params);
+        return mkfailure<value>(str(os), 404, false);
+    }
+
+    // Push patched value to cache
+    const failable<bool> val = memcache::patch(car(params), pval, ch);
+    if (!hasContent(val))
+        return mkfailure<value>(val);
+    return value(content(val));
+}
+
+/**
  * Delete an item from the cache.
  */
 const failable<value> del(const list<value>& params, const memcache::MemCached& ch) {
@@ -98,6 +131,8 @@ const failable<value> start(const list<value>& params) {
             return post(cdr(params), ch);
         if (func == "put")
             return put(cdr(params), ch);
+        if (func == "patch")
+            return patch(cdr(params), ch);
         if (func == "delete")
             return del(cdr(params), ch);
         return mkfailure<value>();
diff --git a/sca-cpp/trunk/components/cache/memcache.hpp b/sca-cpp/trunk/components/cache/memcache.hpp
index 00ee9c6291..7962d1caa0 100644
--- a/sca-cpp/trunk/components/cache/memcache.hpp
+++ b/sca-cpp/trunk/components/cache/memcache.hpp
@@ -73,6 +73,7 @@ private:
 
     friend const failable<bool> post(const value& key, const value& val, const MemCached& cache);
     friend const failable<bool> put(const value& key, const value& val, const MemCached& cache);
+    friend const failable<bool> patch(const value& key, const value& val, const MemCached& cache);
     friend const failable<value> get(const value& key, const MemCached& cache);
     friend const failable<bool> del(const value& key, const MemCached& cache);
 
@@ -177,6 +178,26 @@ const failable<bool> put(const value& key, const value& val, const MemCached& ca
 }
 
 /**
+ * Patch an item in the cache. If the item doesn't exist it is added.
+ */
+const failable<bool> patch(const value& key, const value& val, const MemCached& cache) {
+    debug(key, "memcache::patch::key");
+    debug(val, "memcache::patch::value");
+
+    const string ks(write(content(scheme::writeValue(key))));
+    const string vs(write(content(scheme::writeValue(val))));
+    const apr_status_t rc = apr_memcache_set(cache.mc, nospaces(c_str(ks)), const_cast<char*>(c_str(vs)), length(vs), 0, 27);
+    if (rc != APR_SUCCESS) {
+        ostringstream os;
+        os << "Couldn't set memcached entry: " << key;
+        return mkfailure<bool>(str(os));
+    }
+
+    debug(true, "memcache::patch::result");
+    return true;
+}
+
+/**
  * Get an item from the cache.
  */
 const failable<value> get(const value& key, const MemCached& cache) {
@@ -209,7 +230,7 @@ const failable<bool> del(const value& key, const MemCached& cache) {
     if (rc != APR_SUCCESS) {
         ostringstream os;
         os << "Couldn't delete memcached entry: " << key;
-        return mkfailure<bool>(str(os));
+        return rc == APR_NOTFOUND? mkfailure<bool>(str(os), 404, false) : mkfailure<bool>(str(os));
     }
 
     debug(true, "memcache::delete::result");
diff --git a/sca-cpp/trunk/components/cache/partitioner.cpp b/sca-cpp/trunk/components/cache/partitioner.cpp
index a38c053358..8a56a7f932 100644
--- a/sca-cpp/trunk/components/cache/partitioner.cpp
+++ b/sca-cpp/trunk/components/cache/partitioner.cpp
@@ -143,6 +143,23 @@ const failable<value> put(const value& key, const value& val, const lvvlambda& s
 }
 
 /**
+ * Patch an item in a partition.
+ */
+const failable<value> patch(const value& key, const value& val, const lvvlambda& selector, const list<value>& partitions) {
+
+    // Select partition
+    const failable<list<value> > p = partition(key, selector, partitions);
+    if (!hasContent(p))
+        return mkfailure<value>(p);
+
+    // Path item in selected partition
+    const lvvlambda l = car(content(p));
+    l(mklist<value>("patch", key, val));
+
+    return trueValue;
+}
+
+/**
  * Delete an item from a partition.
  */
 const failable<value> del(const value& key, const lvvlambda& selector, const list<value>& partitions) {
@@ -172,6 +189,8 @@ const tuscany::value apply(const tuscany::list<tuscany::value>& params) {
         return tuscany::partitioner::post(cadr(params), caddr(params), cadddr(params), cddddr(params));
     if (func == "put")
         return tuscany::partitioner::put(cadr(params), caddr(params), cadddr(params), cddddr(params));
+    if (func == "patch")
+        return tuscany::partitioner::patch(cadr(params), caddr(params), cadddr(params), cddddr(params));
     if (func == "delete")
         return tuscany::partitioner::del(cadr(params), caddr(params), cdddr(params));
     return tuscany::mkfailure<tuscany::value>();
diff --git a/sca-cpp/trunk/components/constdb/client-test.cpp b/sca-cpp/trunk/components/constdb/client-test.cpp
index b796ef01dd..165e3d8836 100644
--- a/sca-cpp/trunk/components/constdb/client-test.cpp
+++ b/sca-cpp/trunk/components/constdb/client-test.cpp
@@ -77,6 +77,32 @@ const bool testConstDb() {
         assert(hasContent(val));
         assert(content(val) == b);
     }
+
+    const list<value> k = nilListValue + "content" + (nilListValue + "item" 
+            + (nilListValue + "name" + string("Apple"))
+            + (nilListValue + "price" + string("$3.99")));
+    const list<value> c = nilListValue + (nilListValue + "entry" 
+            + (nilListValue + "title" + string("item"))
+            + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+            + k);
+
+    {
+        const list<value> s = nilListValue + "content" +
+            (nilListValue + "patch" + string("(define (patch id e) (tree-subst-assoc '(price) '(price \"$3.99\") e))"));
+        const list<value> ps = nilListValue + (nilListValue + "entry" 
+                + (nilListValue + "title" + string("item"))
+                + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+                + s);
+
+        const failable<value> r = http::patch(ps, uri + p, cs);
+        assert(hasContent(r));
+        assert(content(r) == trueValue);
+    }
+    {
+        const failable<value> val = http::get(uri + p, cs);
+        assert(hasContent(val));
+        assert(content(val) == c);
+    }
     {
         const failable<value> r = http::del(uri + p, cs);
         assert(hasContent(r));
diff --git a/sca-cpp/trunk/components/constdb/constdb.cpp b/sca-cpp/trunk/components/constdb/constdb.cpp
index a9a5bc5817..2d34ed2b73 100644
--- a/sca-cpp/trunk/components/constdb/constdb.cpp
+++ b/sca-cpp/trunk/components/constdb/constdb.cpp
@@ -63,6 +63,39 @@ const failable<value> put(const list<value>& params, const tinycdb::TinyCDB& cdb
 }
 
 /**
+ * Patch an item in the database.
+ */
+const failable<value> patch(const list<value>& params, const tinycdb::TinyCDB& cdb) {
+    // Read patch
+    value p = assoc<value>("patch", assoc<value>("content", car<value>(cadr(params))));
+    if (isNil(p))
+        return mkfailure<value>("Couldn't read patch script");
+    const string script = cadr<value>(p);
+    debug(script, "tinycdb::patch::script");
+    istringstream is(script);
+
+    // Get existing value from database
+    const failable<value> ival = tinycdb::get(car(params), cdb);
+    if (!hasContent(ival) && rcode(ival) != 404)
+        return mkfailure<value>(ival);
+
+    // Apply patch
+    scheme::Env env = scheme::setupEnvironment();
+    const value pval = scheme::evalScript(cons<value>("patch", scheme::quotedParameters(mklist<value>(car(params), hasContent(ival)? content(ival) : (value)list<value>()))), is, env);
+    if (isNil(pval)) {
+        ostringstream os;
+        os << "Couldn't patch tinycdb entry: " << car(params);
+        return mkfailure<value>(str(os), 404, false);
+    }
+
+    // Push patched value to database
+    const failable<bool> val = tinycdb::patch(car(params), pval, cdb);
+    if (!hasContent(val))
+        return mkfailure<value>(val);
+    return value(content(val));
+}
+
+/**
  * Delete an item from the database.
  */
 const failable<value> del(const list<value>& params, const tinycdb::TinyCDB& cdb) {
@@ -89,6 +122,8 @@ const failable<value> start(unused const list<value>& params) {
             return post(cdr(params), cdb);
         if (func == "put")
             return put(cdr(params), cdb);
+        if (func == "patch")
+            return patch(cdr(params), cdb);
         if (func == "delete")
             return del(cdr(params), cdb);
         return mkfailure<value>();
diff --git a/sca-cpp/trunk/components/constdb/tinycdb-test.cpp b/sca-cpp/trunk/components/constdb/tinycdb-test.cpp
index 6cc9e9eabb..41bfe12772 100644
--- a/sca-cpp/trunk/components/constdb/tinycdb-test.cpp
+++ b/sca-cpp/trunk/components/constdb/tinycdb-test.cpp
@@ -40,6 +40,8 @@ const bool testTinyCDB() {
     assert((get(k, cdb)) == value(string("AAA")));
     assert(hasContent(put(k, string("aaa"), cdb)));
     assert((get(k, cdb)) == value(string("aaa")));
+    assert(hasContent(patch(k, string("bbb"), cdb)));
+    assert((get(k, cdb)) == value(string("bbb")));
     assert(hasContent(del(k, cdb)));
     assert(!hasContent(get(k, cdb)));
 
diff --git a/sca-cpp/trunk/components/constdb/tinycdb.hpp b/sca-cpp/trunk/components/constdb/tinycdb.hpp
index ce1dcbb011..3da5f3c216 100644
--- a/sca-cpp/trunk/components/constdb/tinycdb.hpp
+++ b/sca-cpp/trunk/components/constdb/tinycdb.hpp
@@ -389,6 +389,37 @@ const failable<bool> put(const value& key, const value& val, const TinyCDB& cdb)
 }
 
 /**
+ * Patch an item in the database. If the item doesn't exist it is added.
+ */
+const failable<bool> patch(const value& key, const value& val, const TinyCDB& cdb) {
+    debug(key, "tinycdb::patch::key");
+    debug(val, "tinycdb::patch::value");
+    debug(dbname(cdb), "tinycdb::patch::dbname");
+
+    const string ks(write(content(scheme::writeValue(key))));
+    const string vs(write(content(scheme::writeValue(val))));
+
+    // Process each entry and skip existing key
+    const lambda<const failable<bool>(buffer&, const unsigned int, const unsigned int)> update = [ks](buffer& buf, const unsigned int klen, unused const unsigned int vlen) -> const failable<bool> {
+        if (ks == string((char*)buf, klen))
+            return false;
+        return true;
+    };
+
+    // Add the new entry to the db
+    const lambda<const failable<bool>(struct cdb_make&)> finish = [ks, vs](struct cdb_make& cdbm) -> const failable<bool> {
+        if (cdb_make_add(&cdbm, c_str(ks), (unsigned int)length(ks), c_str(vs), (unsigned int)length(vs)) == -1)
+            return mkfailure<bool>(string("Couldn't add tinycdb entry: ") + ks);
+        return true;
+    };
+
+    // Rewrite the db
+    const failable<bool> r = rewrite(update, finish, cdb);
+    debug(r, "tinycdb::patch::result");
+    return r;
+}
+
+/**
  * Get an item from the database.
  */
 const failable<value> get(const value& key, const TinyCDB& cdb) {
@@ -425,11 +456,14 @@ const failable<bool> del(const value& key, const TinyCDB& cdb) {
     debug(dbname(cdb), "tinycdb::delete::dbname");
 
     const string ks(write(content(scheme::writeValue(key))));
+    bool found = false;
 
     // Process each entry and skip existing key
-    const lambda<const failable<bool>(buffer&, const unsigned int, const unsigned int)> update = [ks](buffer& buf, const unsigned int klen, unused const unsigned int vlen) -> const failable<bool> {
-        if (ks == string((char*)buf, klen))
+    const lambda<const failable<bool>(buffer&, const unsigned int, const unsigned int)> update = [ks, &found](buffer& buf, const unsigned int klen, unused const unsigned int vlen) -> const failable<bool> {
+        if (ks == string((char*)buf, klen)) {
+            found = true;
             return false;
+        }
         return true;
     };
 
@@ -440,6 +474,11 @@ const failable<bool> del(const value& key, const TinyCDB& cdb) {
 
     // Rewrite the db
     const failable<bool> r = rewrite(update, finish, cdb);
+    if (!hasContent(r) || !found) {
+        ostringstream os;
+        os << "Couldn't delete tinycdb entry: " << key;
+        return hasContent(r)? mkfailure<bool>(str(os), 404, false) : r;
+    }
     debug(r, "tinycdb::delete::result");
     return r;
 }
diff --git a/sca-cpp/trunk/components/filedb/client-test.cpp b/sca-cpp/trunk/components/filedb/client-test.cpp
index 5694d97522..96c0212096 100644
--- a/sca-cpp/trunk/components/filedb/client-test.cpp
+++ b/sca-cpp/trunk/components/filedb/client-test.cpp
@@ -77,6 +77,32 @@ const bool testFileDB() {
         assert(hasContent(val));
         assert(content(val) == b);
     }
+
+    const list<value> k = nilListValue + "content" + (nilListValue + "item" 
+            + (nilListValue + "name" + string("Apple"))
+            + (nilListValue + "price" + string("$3.99")));
+    const list<value> c = nilListValue + (nilListValue + "entry" 
+            + (nilListValue + "title" + string("item"))
+            + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+            + k);
+
+    {
+        const list<value> s = nilListValue + "content" +
+            (nilListValue + "patch" + string("(define (patch id e) (tree-subst-assoc '(price) '(price \"$3.99\") e))"));
+        const list<value> ps = nilListValue + (nilListValue + "entry" 
+                + (nilListValue + "title" + string("item"))
+                + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+                + s);
+
+        const failable<value> r = http::patch(ps, uri + p, cs);
+        assert(hasContent(r));
+        assert(content(r) == trueValue);
+    }
+    {
+        const failable<value> val = http::get(uri + p, cs);
+        assert(hasContent(val));
+        assert(content(val) == c);
+    }
     {
         const failable<value> r = http::del(uri + p, cs);
         assert(hasContent(r));
diff --git a/sca-cpp/trunk/components/filedb/file-test.cpp b/sca-cpp/trunk/components/filedb/file-test.cpp
index 5270967ccb..55272800f0 100644
--- a/sca-cpp/trunk/components/filedb/file-test.cpp
+++ b/sca-cpp/trunk/components/filedb/file-test.cpp
@@ -38,11 +38,14 @@ const bool testFileDB(const string& dbname, const string& format) {
 
     const list<value> a = mklist<value>(nilListValue + "ns1:a" + (nilListValue + "@xmlns:ns1" + string("http://aaa")) + (nilListValue + "text" + string("Hey!")));
     const list<value> b = mklist<value>(nilListValue + "ns1:b" + (nilListValue + "@xmlns:ns1" + string("http://bbb")) + (nilListValue + "text" + string("Hey!")));
+    const list<value> c = mklist<value>(nilListValue + "ns1:c" + (nilListValue + "@xmlns:ns1" + string("http://ccc")) + (nilListValue + "text" + string("Hey!")));
 
     assert(hasContent(post(k, a, db)));
     assert((get(k, db)) == value(a));
     assert(hasContent(put(k, b, db)));
     assert((get(k, db)) == value(b));
+    assert(hasContent(patch(k, c, db)));
+    assert((get(k, db)) == value(c));
     assert(hasContent(del(k, db)));
     assert(!hasContent(get(k, db)));
     assert(hasContent(post(k, a, db)));
diff --git a/sca-cpp/trunk/components/filedb/filedb.cpp b/sca-cpp/trunk/components/filedb/filedb.cpp
index 37cb6c5260..b28cc9bedb 100644
--- a/sca-cpp/trunk/components/filedb/filedb.cpp
+++ b/sca-cpp/trunk/components/filedb/filedb.cpp
@@ -63,6 +63,39 @@ const failable<value> put(const list<value>& params, const filedb::FileDB& db) {
 }
 
 /**
+ * Patch an item in the database.
+ */
+const failable<value> patch(const list<value>& params, const filedb::FileDB& db) {
+    // Read patch
+    value p = assoc<value>("patch", assoc<value>("content", car<value>(cadr(params))));
+    if (isNil(p))
+        return mkfailure<value>("Couldn't read patch script");
+    const string script = cadr<value>(p);
+    debug(script, "filedb::patch::script");
+    istringstream is(script);
+
+    // Get existing value from database
+    const failable<value> ival = filedb::get(car(params), db);
+    if (!hasContent(ival) && rcode(ival) != 404)
+        return mkfailure<value>(ival);
+
+    // Apply patch
+    scheme::Env env = scheme::setupEnvironment();
+    const value pval = scheme::evalScript(cons<value>("patch", scheme::quotedParameters(mklist<value>(car(params), hasContent(ival)? content(ival) : (value)list<value>()))), is, env);
+    if (isNil(pval)) {
+        ostringstream os;
+        os << "Couldn't patch file database entry: " << car(params);
+        return mkfailure<value>(str(os), 404, false);
+    }
+
+    // Push patched value to database
+    const failable<bool> val = filedb::patch(car(params), pval, db);
+    if (!hasContent(val))
+        return mkfailure<value>(val);
+    return value(content(val));
+}
+
+/**
  * Delete an item from the database.
  */
 const failable<value> del(const list<value>& params, const filedb::FileDB& db) {
@@ -91,6 +124,8 @@ const failable<value> start(const list<value>& params) {
             return post(cdr(params), db);
         if (func == "put")
             return put(cdr(params), db);
+        if (func == "patch")
+            return patch(cdr(params), db);
         if (func == "delete")
             return del(cdr(params), db);
         return mkfailure<value>();
diff --git a/sca-cpp/trunk/components/filedb/filedb.hpp b/sca-cpp/trunk/components/filedb/filedb.hpp
index 2855cebfc6..41dde88bef 100644
--- a/sca-cpp/trunk/components/filedb/filedb.hpp
+++ b/sca-cpp/trunk/components/filedb/filedb.hpp
@@ -82,6 +82,7 @@ private:
     friend const failable<value> read(istream& is, const string& format);
     friend const failable<bool> post(const value& key, const value& val, const FileDB& db);
     friend const failable<bool> put(const value& key, const value& val, const FileDB& db);
+    friend const failable<bool> patch(const value& key, const value& val, const FileDB& db);
     friend const failable<value> get(const value& key, const FileDB& db);
     friend const failable<bool> del(const value& key, const FileDB& db);
 };
@@ -208,6 +209,30 @@ const failable<bool> put(const value& key, const value& val, const FileDB& db) {
 }
 
 /**
+ * Patch an item in the database. If the item doesn't exist it is added.
+ */
+const failable<bool> patch(const value& key, const value& val, const FileDB& db) {
+    debug(key, "filedb::patch::key");
+    debug(val, "filedb::patch::value");
+    debug(db.name, "filedb::patch::dbname");
+
+    if (isList(key))
+        mkdirs(key, db.name);
+    const string fn = filename(key, db.name);
+    debug(fn, "filedb::patch::filename");
+    ofstream os(fn);
+    if (os.fail()) {
+        ostringstream os;
+        os << "Couldn't patch file database entry: " << key;
+        return mkfailure<bool>(str(os));
+    }
+    const failable<bool> r = write(val, os, db.format);
+
+    debug(r, "filedb::patch::result");
+    return r;
+}
+
+/**
  * Get an item from the database.
  */
 const failable<value> get(const value& key, const FileDB& db) {
@@ -241,7 +266,7 @@ const failable<bool> del(const value& key, const FileDB& db) {
     if (rc == -1) {
         ostringstream os;
         os << "Couldn't delete file database entry: " << key;
-        return mkfailure<bool>(str(os));
+        return errno == ENOENT? mkfailure<bool>(str(os), 404, false) : mkfailure<bool>(str(os));
     }
 
     debug(true, "filedb::delete::result");
diff --git a/sca-cpp/trunk/components/sqldb/client-test.cpp b/sca-cpp/trunk/components/sqldb/client-test.cpp
index c9fbb7d5bb..fcdb8d3c2a 100644
--- a/sca-cpp/trunk/components/sqldb/client-test.cpp
+++ b/sca-cpp/trunk/components/sqldb/client-test.cpp
@@ -77,6 +77,32 @@ const bool testSqlDb() {
         assert(hasContent(val));
         assert(content(val) == b);
     }
+
+    const list<value> k = nilListValue + "content" + (nilListValue + "item" 
+            + (nilListValue + "name" + string("Apple"))
+            + (nilListValue + "price" + string("$3.99")));
+    const list<value> c = nilListValue + (nilListValue + "entry" 
+            + (nilListValue + "title" + string("item"))
+            + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+            + k);
+
+    {
+        const list<value> s = nilListValue + "content" +
+            (nilListValue + "patch" + string("(define (patch id e) (tree-subst-assoc '(price) '(price \"$3.99\") e))"));
+        const list<value> ps = nilListValue + (nilListValue + "entry" 
+                + (nilListValue + "title" + string("item"))
+                + (nilListValue + "id" + string("cart-53d67a61-aa5e-4e5e-8401-39edeba8b83b"))
+                + s);
+
+        const failable<value> r = http::patch(ps, uri + p, cs);
+        assert(hasContent(r));
+        assert(content(r) == trueValue);
+    }
+    {
+        const failable<value> val = http::get(uri + p, cs);
+        assert(hasContent(val));
+        assert(content(val) == c);
+    }
     {
         const failable<value> r = http::del(uri + p, cs);
         assert(hasContent(r));
diff --git a/sca-cpp/trunk/components/sqldb/pgsql-conf b/sca-cpp/trunk/components/sqldb/pgsql-conf
index 8adbb902c9..020ce129fb 100755
--- a/sca-cpp/trunk/components/sqldb/pgsql-conf
+++ b/sca-cpp/trunk/components/sqldb/pgsql-conf
@@ -96,6 +96,7 @@ archive_command = '$here/pgsql-archive $root $host $bport %p %f'
 wal_level = hot_standby
 max_wal_senders = 5
 wal_keep_segments = 32
+#synchronous_standby_names = '*'
 
 EOF
 
@@ -166,7 +167,6 @@ cat >$root/sqldb/data/pgbouncer.conf <<EOF
 db = host=$host port=$port dbname=db user=bouncer
 
 [pgbouncer]
-pool_mode = session
 listen_addr = $listen
 listen_port = $bport
 unix_socket_dir =
@@ -177,9 +177,9 @@ pidfile = $root/logs/pgbouncer.pid
 max_client_conn = 1000
 pool_mode = transaction
 server_reset_query =
-default_pool_size = 500
+default_pool_size = 50
 min_pool_size = 5
-reserve_pool_size = 50
+reserve_pool_size = 5
 log_connections = 0
 log_disconnections = 0
 stats_period = 3600
diff --git a/sca-cpp/trunk/components/sqldb/pgsql-standby-conf b/sca-cpp/trunk/components/sqldb/pgsql-standby-conf
index 5f76b5b332..ae2ed8e909 100755
--- a/sca-cpp/trunk/components/sqldb/pgsql-standby-conf
+++ b/sca-cpp/trunk/components/sqldb/pgsql-standby-conf
@@ -126,7 +126,7 @@ cat >$root/sqldb/data/recovery.conf << EOF
 
 # Start in standby mode
 standby_mode = 'on'
-primary_conninfo = 'host=$mhost port=$mport user=standby'
+primary_conninfo = 'host=$mhost port=$mport user=standby application_name=$host:$port'
 
 # Failover
 trigger_file = '$root/sqldb/failover'
@@ -165,7 +165,6 @@ cat >$root/sqldb/data/pgbouncer.conf <<EOF
 db = host=$host port=$port dbname=db user=bouncer
 
 [pgbouncer]
-pool_mode = session
 listen_addr = $listen
 listen_port = $bport
 unix_socket_dir =
@@ -176,9 +175,9 @@ pidfile = $root/logs/pgbouncer.pid
 max_client_conn = 1000
 pool_mode = transaction
 server_reset_query =
-default_pool_size = 500
+default_pool_size = 50
 min_pool_size = 5
-reserve_pool_size = 50
+reserve_pool_size = 5
 log_connections = 0
 log_disconnections = 0
 stats_period = 3600
diff --git a/sca-cpp/trunk/components/sqldb/pgsql-standby-test.cpp b/sca-cpp/trunk/components/sqldb/pgsql-standby-test.cpp
index 5d73b0d877..319194ab41 100644
--- a/sca-cpp/trunk/components/sqldb/pgsql-standby-test.cpp
+++ b/sca-cpp/trunk/components/sqldb/pgsql-standby-test.cpp
@@ -43,6 +43,9 @@ const bool testPGSql() {
     assert(hasContent(put(k, string("aaa"), wpg)));
     sleep(1);
     assert((get(k, rpg)) == value(string("aaa")));
+    assert(hasContent(patch(k, string("bbb"), wpg)));
+    sleep(1);
+    assert((get(k, rpg)) == value(string("bbb")));
     assert(hasContent(del(k, wpg)));
     sleep(1);
     assert(!hasContent(get(k, rpg)));
diff --git a/sca-cpp/trunk/components/sqldb/pgsql-test.cpp b/sca-cpp/trunk/components/sqldb/pgsql-test.cpp
index 5d7bb98cd8..ec5d537b44 100644
--- a/sca-cpp/trunk/components/sqldb/pgsql-test.cpp
+++ b/sca-cpp/trunk/components/sqldb/pgsql-test.cpp
@@ -49,6 +49,8 @@ const bool testPGSql() {
 
     assert(hasContent(put(k, string("aaa"), pg)));
     assert(content(get(k, pg)) == value(string("aaa")));
+    assert(hasContent(patch(k, string("bbb"), pg)));
+    assert(content(get(k, pg)) == value(string("bbb")));
     assert(hasContent(del(k, pg)));
     assert(!hasContent(get(k, pg)));
 
diff --git a/sca-cpp/trunk/components/sqldb/pgsql.hpp b/sca-cpp/trunk/components/sqldb/pgsql.hpp
index 620aec4105..5e0004c4e6 100644
--- a/sca-cpp/trunk/components/sqldb/pgsql.hpp
+++ b/sca-cpp/trunk/components/sqldb/pgsql.hpp
@@ -75,12 +75,15 @@ public:
         string ks = string("select a.attname from pg_attribute a, pg_class c where a.attrelid = c.relfilenode and c.relname = '") + table + string("' and a.attnum in (1, 2) order by a.attnum;");
         PGresult* const kr = PQexec(conn, c_str(ks));
         if (PQresultStatus(kr) != PGRES_TUPLES_OK) {
-            mkfailure<bool>(string("Couldn't execute postgresql column select statement: ") + pgfailure(kr, conn));
+            const string rs = string("Couldn't execute postgresql column select statement: ") + pgfailure(kr, conn);
+            PQclear(kr);
+            mkfailure<bool>(rs);
             return;
         }
         if (PQntuples(kr) != 2) {
+            const string rs = "Couldn't find postgresql table key and value column names";
             PQclear(kr);
-            mkfailure<bool>(string("Couldn't find postgresql table key and value column names"));
+            mkfailure<bool>(rs);
             return;
         }
         kname = c_str(string(PQgetvalue(kr, 0, 0)));
@@ -95,12 +98,10 @@ public:
     PGSql& operator=(const PGSql& c) = delete;
 
     ~PGSql() {
-        debug("pgsql::~pgsql");
         if (!owner)
             return;
         if (conn == NULL)
             return;
-        debug(conn, "pgsql::~pgsql::conn");
         PQfinish(conn);
     }
 
@@ -113,8 +114,12 @@ private:
     const char* vname;
 
     friend const failable<bool> setup(const PGSql& pgsql);
+    friend const failable<bool> begin(const PGSql& pgsql);
+    friend const failable<bool> commit(const PGSql& pgsql);
+    friend const failable<bool> rollback(const PGSql& pgsql);
     friend const failable<bool> post(const value& key, const value& val, const PGSql& pgsql);
     friend const failable<bool> put(const value& key, const value& val, const PGSql& pgsql);
+    friend const failable<bool> patch(const value& key, const value& val, const PGSql& pgsql);
     friend const failable<value> get(const value& key, const PGSql& pgsql);
     friend const failable<bool> del(const value& key, const PGSql& pgsql);
 };
@@ -134,6 +139,69 @@ const failable<bool> setup(const PGSql& pgsql) {
 }
 
 /**
+ * Begin a database transaction.
+ */
+const failable<bool> begin(const PGSql& pgsql) {
+    debug("pgsql::begin");
+    debug(pgsql.conninfo, "pgsql::begin::conninfo");
+    debug(pgsql.table, "pgsql::begin::table");
+    setup(pgsql);
+
+    PGresult* const r = PQexec(pgsql.conn, "begin transaction isolation level repeatable read");
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute begin SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
+    PQclear(r);
+
+    debug(true, "pgsql::begin::result");
+    return true;
+}
+
+/**
+ * Commit a database transaction.
+ */
+const failable<bool> commit(const PGSql& pgsql) {
+    debug("pgsql::commit");
+    debug(pgsql.conninfo, "pgsql::commit::conninfo");
+    debug(pgsql.table, "pgsql::commit::table");
+    setup(pgsql);
+
+    PGresult* const r = PQexec(pgsql.conn, "commit");
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute commit SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
+    PQclear(r);
+
+    debug(true, "pgsql::commit::result");
+    return true;
+}
+
+/**
+ * Rollback a database transaction.
+ */
+const failable<bool> rollback(const PGSql& pgsql) {
+    debug("pgsql::rollback");
+    debug(pgsql.conninfo, "pgsql::rollback::conninfo");
+    debug(pgsql.table, "pgsql::rollback::table");
+    setup(pgsql);
+
+    PGresult* const r = PQexec(pgsql.conn, "rollback");
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute rollback SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
+    PQclear(r);
+
+    debug(true, "pgsql::rollback::result");
+    return true;
+}
+
+/**
  * Post a new item to the database.
  */
 const failable<bool> post(const value& key, const value& val, const PGSql& pgsql) {
@@ -147,8 +215,11 @@ const failable<bool> post(const value& key, const value& val, const PGSql& pgsql
     const string vs(write(content(scheme::writeValue(val))));
     const char* const params[2] = { c_str(ks), c_str(vs) };
     PGresult* const r = PQexecParams(pgsql.conn, c_str(string("insert into ") + pgsql.table + string(" values($1, $2);")), 2, NULL, params, NULL, NULL, 0);
-    if (PQresultStatus(r) != PGRES_COMMAND_OK)
-        return mkfailure<bool>(string("Couldn't execute insert postgresql SQL statement: ") + pgfailure(r, pgsql.conn));
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute insert postgresql SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
     PQclear(r);
 
     debug(true, "pgsql::post::result");
@@ -169,10 +240,13 @@ const failable<bool> put(const value& key, const value& val, const PGSql& pgsql)
     const string vs(write(content(scheme::writeValue(val))));
     const char* const params[2] = { c_str(ks), c_str(vs) };
     PGresult* const r = PQexecParams(pgsql.conn, c_str(string("update ") + pgsql.table + string(" set ") + pgsql.vname + string(" = $2 where ") + pgsql.kname + string(" = $1;")), 2, NULL, params, NULL, NULL, 0);
-    if (PQresultStatus(r) != PGRES_COMMAND_OK)
-        return mkfailure<bool>(string("Couldn't execute update postgresql SQL statement: ") + pgfailure(r, pgsql.conn));
-    const string t = PQcmdTuples(r);
-    if (t != "0") {
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute update postgresql SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
+    const char* const t = PQcmdTuples(r);
+    if (t != NULL && strcmp(t, "0")) {
         PQclear(r);
         debug(true, "pgsql::put::result");
         return true;
@@ -180,8 +254,11 @@ const failable<bool> put(const value& key, const value& val, const PGSql& pgsql)
     PQclear(r);
 
     PGresult* const pr = PQexecParams(pgsql.conn, c_str(string("insert into ") + pgsql.table + string(" values($1, $2);")), 2, NULL, params, NULL, NULL, 0);
-    if (PQresultStatus(pr) != PGRES_COMMAND_OK)
-        return mkfailure<bool>(string("Couldn't execute insert postgresql SQL statement: ") + pgfailure(pr, pgsql.conn));
+    if (PQresultStatus(pr) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute insert postgresql SQL statement: ") + pgfailure(pr, pgsql.conn);
+        PQclear(pr);
+        return mkfailure<bool>(rs);
+    }
     PQclear(pr);
 
     debug(true, "pgsql::put::result");
@@ -189,6 +266,57 @@ const failable<bool> put(const value& key, const value& val, const PGSql& pgsql)
 }
 
 /**
+ * Patch an item in the database. If the item doesn't exist it is added.
+ */
+const failable<bool> patch(const value& key, const value& val, const PGSql& pgsql) {
+    debug(key, "pgsql::patch::key");
+    debug(val, "pgsql::patch::value");
+    debug(pgsql.conninfo, "pgsql::patch::conninfo");
+    debug(pgsql.table, "pgsql::patch::table");
+    setup(pgsql);
+
+    const string ks(write(content(scheme::writeValue(key))));
+    const string vs(write(content(scheme::writeValue(val))));
+    const char* const params[2] = { c_str(ks), c_str(vs) };
+    PGresult* const r = PQexecParams(pgsql.conn, c_str(string("update ") + pgsql.table + string(" set ") + pgsql.vname + string(" = $2 where ") + pgsql.kname + string(" = $1;")), 2, NULL, params, NULL, NULL, 0);
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute update postgresql SQL statement: ") + pgfailure(r, pgsql.conn);
+        const char* const st = PQresultErrorField(r, PG_DIAG_SQLSTATE);
+        if (st != NULL && !strncmp(st, "40", 2)) {
+
+            // Report a transaction serialization conflict
+            PQclear(r);
+            return mkfailure<bool>(rs, 409);
+        }
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
+    const char* const t = PQcmdTuples(r);
+    if (t != NULL && strcmp(t, "0")) {
+        PQclear(r);
+        debug(true, "pgsql::patch::result");
+        return true;
+    }
+    PQclear(r);
+
+    PGresult* const pr = PQexecParams(pgsql.conn, c_str(string("insert into ") + pgsql.table + string(" values($1, $2);")), 2, NULL, params, NULL, NULL, 0);
+    if (PQresultStatus(pr) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute insert postgresql SQL statement: ") + pgfailure(pr, pgsql.conn);
+        const char* const st = PQresultErrorField(pr, PG_DIAG_SQLSTATE);
+        if (st != NULL && !strncmp(st, "40", 2)) {
+            PQclear(pr);
+            return mkfailure<bool>(rs, 40);
+        }
+        PQclear(pr);
+        return mkfailure<bool>(rs);
+    }
+    PQclear(pr);
+
+    debug(true, "pgsql::patch::result");
+    return true;
+}
+
+/**
  * Convert a key to an item id.
  */
 const list<value> keyid(const list<value>& key) {
@@ -200,14 +328,14 @@ const list<value> keyid(const list<value>& key) {
 }
 
 /**
- * Convert a key to an param name / value assoc.
+ * Convert a key to a (param name, value) assoc.
  */
-const list<list<value> > keyparams(const list<value>& key) {
+const list<value> keyparams(const list<value>& key) {
     if (isNil(key))
         return nilListValue;
     if (!isList(car(key)))
         return keyparams(cdr(key));
-    return cons<list<value> >((list<value>)car(key), keyparams(cdr(key)));
+    return cons<value>(car(key), keyparams(cdr(key)));
 }
 
 /**
@@ -216,9 +344,8 @@ const list<list<value> > keyparams(const list<value>& key) {
 const list<value> getitems(PGresult* const r, const int i, const int n) {
     if (i == n)
         return nilListValue;
-    const value key(content(scheme::readValue(string(PQgetvalue(r, i, 0)))));
     const value val(content(scheme::readValue(string(PQgetvalue(r, i, 1)))));
-    return cons<value>(mklist<value>(key, val), getitems(r, i + 1, n));
+    return cons<value>(val, getitems(r, i + 1, n));
 }
 
 /**
@@ -250,12 +377,13 @@ const failable<value> get(const value& key, const PGSql& pgsql) {
 
     // Get item and id and get parameters from the key
     const bool lk = isList(key);
-    const list<list<value> > kparams = lk? keyparams(key) : list<list<value> >();
+    const list<value> kparams = lk? keyparams(key) : nilListValue;
     const list<value> regex = assoc<value>("regex", kparams);
     const list<value> like = assoc<value>("like", kparams);
     const list<value> textsearch = assoc<value>("textsearch", kparams);
     const list<value> limit = assoc<value>("limit", kparams);
     const list<value> offset = assoc<value>("offset", kparams);
+    const list<value> rank = assoc<value>("rank", kparams);
     const list<value> id = lk? keyid(key) : nilListValue;
     const list<value> atable = assoc<value>("table", kparams);
     const string table = isNil(atable)? pgsql.table : (string)cadr(atable);
@@ -265,14 +393,20 @@ const failable<value> get(const value& key, const PGSql& pgsql) {
     const string vname = isNil(avname)? pgsql.vname : (string)cadr(avname);
 
     // Build the SQL query
-    const char* sqlparams[5];
+    const char* sqlparams[6];
     int p = 0;
     int w = 0;
     ostringstream sqlos;
-    sqlos << "select data.*";
+    sqlos << "select data." << kname << ", data." << vname;
     if (!isNil(textsearch)) {
-        // Text search, setup result ranking
-        sqlos << ", ts_rank_cd(to_tsvector(data." << vname << "), tsquery, 32) as rank";
+        // Text search, setup text result ranking
+        sqlos << ", ts_rank_cd(to_tsvector(data." << vname << "), tsquery, 32) as tsrank";
+    }
+    if (!isNil(rank)) {
+        // Ranking, setup rank expression
+        const string rs = (string)cadr(rank);
+        sqlparams[p++] = c_str(rs);
+        sqlos << ", $" << p << " as rank";
     }
     sqlos << " from " << table << " data";
     if (!isNil(textsearch)) {
@@ -305,9 +439,13 @@ const failable<value> get(const value& key, const PGSql& pgsql) {
     if (!isNil(textsearch)) {
         // Text search, apply the query
         sqlos << (w == 0? " where" : " and");
-        sqlos << " tsquery @@ to_tsvector(data." << vname << ") order by rank desc";
+        sqlos << " tsquery @@ to_tsvector(data." << vname << ")";
         w++;
     }
+    if (!isNil(textsearch) || !isNil(rank)) {
+        // Result ordering
+        sqlos << " order by" << (isNil(rank)? "" : " rank desc") << ((isNil(rank) || isNil(textsearch))? "" : ",") << (isNil(textsearch)? "" : " tsrank desc");
+    }
     if (!isNil(offset)) {
         // Result pagination offset
         sqlos << " offset " << atoi(c_str((string)cadr(offset)));
@@ -320,8 +458,11 @@ const failable<value> get(const value& key, const PGSql& pgsql) {
     const string sqls = str(sqlos);
     debug(sqls, "pgsql::get::sqls");
     PGresult* r = PQexecParams(pgsql.conn, c_str(sqls), p, NULL, sqlparams, NULL, NULL, 0);
-    if (PQresultStatus(r) != PGRES_TUPLES_OK)
-        return mkfailure<value>(string("Couldn't execute select postgresql SQL statement: ") + pgfailure(r, pgsql.conn));
+    if (PQresultStatus(r) != PGRES_TUPLES_OK) {
+        const string rs = string("Couldn't execute select postgresql SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<value>(rs);
+    }
     const int n = PQntuples(r);
     if (n < 1) {
         PQclear(r);
@@ -330,7 +471,7 @@ const failable<value> get(const value& key, const PGSql& pgsql) {
         return mkfailure<value>(str(os), 404, false);
     }
 
-    // Return a collection of key / item pairs
+    // Return a collection of items
     if (l != 1) {
         const list<value> lval = getitems(r, 0, n);
         PQclear(r);
@@ -357,8 +498,18 @@ const failable<bool> del(const value& key, const PGSql& pgsql) {
     const string ks(write(content(scheme::writeValue(key))));
     const char* const params[1] = { c_str(ks) };
     PGresult* const r = PQexecParams(pgsql.conn, c_str(string("delete from ") + pgsql.table + string(" where ") + pgsql.kname + string(" = $1;")), 1, NULL, params, NULL, NULL, 0);
-    if (PQresultStatus(r) != PGRES_COMMAND_OK)
-        return mkfailure<bool>(string("Couldn't execute delete postgresql SQL statement: ") + pgfailure(r, pgsql.conn));
+    if (PQresultStatus(r) != PGRES_COMMAND_OK) {
+        const string rs = string("Couldn't execute delete postgresql SQL statement: ") + pgfailure(r, pgsql.conn);
+        PQclear(r);
+        return mkfailure<bool>(rs);
+    }
+    const char* const t = PQcmdTuples(r);
+    if (t != NULL && !strcmp(t, "0")) {
+        PQclear(r);
+        ostringstream os;
+        os << "Couldn't delete postgresql entry: " << key;
+        return mkfailure<bool>(str(os), 404, false);
+    }
     PQclear(r);
 
     debug(true, "pgsql::delete::result");
diff --git a/sca-cpp/trunk/components/sqldb/sqldb.cpp b/sca-cpp/trunk/components/sqldb/sqldb.cpp
index 1288dd553b..75be2c0624 100644
--- a/sca-cpp/trunk/components/sqldb/sqldb.cpp
+++ b/sca-cpp/trunk/components/sqldb/sqldb.cpp
@@ -64,6 +64,65 @@ const failable<value> put(const list<value>& params, const pgsql::PGSql& pg) {
 }
 
 /**
+ * Patch an item in the database.
+ */
+const failable<value> patch(const list<value>& params, const pgsql::PGSql& pg) {
+    // Read patch
+    value p = assoc<value>("patch", assoc<value>("content", car<value>(cadr(params))));
+    if (isNil(p))
+        return mkfailure<value>("Couldn't read patch script");
+    const string script = cadr<value>(p);
+    debug(script, "pgsql::patch::script");
+
+    const lambda<const failable<value>(const value&, const pgsql::PGSql&, const string&, const int)> tryPatch = [&tryPatch](const value& key, const pgsql::PGSql& pg, const string& script, const int count) -> const failable<value> {
+
+        // Begin database transaction
+        const failable<bool> brc = pgsql::begin(pg);
+        if (!hasContent(brc))
+            return mkfailure<value>(brc);
+
+        // Get existing value from database
+        const failable<value> ival = pgsql::get(key, pg);
+        if (!hasContent(ival) && rcode(ival) != 404) {
+            pgsql::rollback(pg);
+            return mkfailure<value>(ival);
+        }
+
+        // Apply patch
+        istringstream is(script);
+        scheme::Env env = scheme::setupEnvironment();
+        const value pval = scheme::evalScript(cons<value>("patch", scheme::quotedParameters(mklist<value>(key, hasContent(ival)? content(ival) : (value)list<value>()))), is, env);
+        if (isNil(pval)) {
+            ostringstream os;
+            os << "Couldn't patch postgresql entry: " << key;
+            return mkfailure<value>(str(os), 404, false);
+        }
+
+        // Push patched value to database
+        const failable<bool> val = pgsql::patch(key, pval, pg);
+        if (!hasContent(val)) {
+            pgsql::rollback(pg);
+
+            // Retry on a transaction serialization error
+            if (rcode(val) == 409 && count > 0)
+                return tryPatch(key, pg, script, count - 1);
+            return mkfailure<value>(val);
+        }
+
+        // Commit database transaction
+        const failable<bool> crc = pgsql::commit(pg);
+        if (!hasContent(crc))
+            return mkfailure<value>(crc);
+
+        return value(content(val));
+    };
+
+    // Try patching the entry and automatically retry a few times on transaction
+    // serialization errors
+    return tryPatch(car(params), pg, script, 5);
+}
+
+/**
  * Delete an item from the database.
  */
 const failable<value> del(const list<value>& params, const pgsql::PGSql& pg) {
@@ -98,6 +157,8 @@ const failable<value> start(const list<value>& params) {
             return post(cdr(params), *pg);
         if (func == "put")
             return put(cdr(params), *pg);
+        if (func == "patch")
+            return patch(cdr(params), *pg);
         if (func == "delete")
             return del(cdr(params), *pg);
         return mkfailure<value>();