Improve API to take into account sqlite pragma for column introspection

docs/utilities.md

@@ -141,7 +141,7 @@ Similarly, to get the description of all columns in the given table:
 
 ```cpp
 soci::column_info ci;
-soci::statement st = (sql.prepare_column_descriptions(table_name), into(ci));
+soci::statement st = sql.prepare_column_descriptions(table_name, ci);
 
 st.execute();
 while (st.fetch())

include/soci/session.h

@@ -138,13 +138,16 @@ class SOCI_DECL session
     // it makes sense to bind std::string for the output field.
     details::prepare_temp_type prepare_table_names();
 
+    [[deprecated("Use the overload prepare_column_descriptions with column_info to support more backends (i.e. sqlite)")]]
+    details::prepare_temp_type prepare_column_descriptions(std::string & table_name);
+
     // Returns prepare_temp_type for the internally composed query
     // for the list of column descriptions.
     // Since this is intended for use with statement objects, where results are obtained one row after another,
     // it makes sense to bind either std::string for each output field or soci::column_info for the whole row.
     // Note: table_name is a non-const reference to prevent temporary objects,
     // this argument is bound as a regular "use" element.
-    details::prepare_temp_type prepare_column_descriptions(std::string & table_name);
+    details::prepare_temp_type prepare_column_descriptions(std::string & table_name, soci::column_info & info);
 
     // Functions for basic portable DDL statements.
 

include/soci/soci-backend.h

@@ -301,6 +301,12 @@ class session_backend
             " where table_schema = 'public' and table_name = :t";
     }
 
+    virtual details::prepare_temp_type prepare_column_descriptions_statement(
+            details::prepare_type& prepare, std::string & table_name, soci::column_info& info) const
+    {
+        return prepare << get_column_descriptions_query(), soci::use(table_name, "t"), soci::into(info);
+    }
+
     virtual std::string create_table(const std::string & tableName)
     {
         return "create table " + tableName + " (";

include/soci/sqlite3/soci-sqlite3.h

@@ -307,6 +307,12 @@ struct sqlite3_session_backend : details::session_backend
         return "select name as \"TABLE_NAME\""
                 " from sqlite_master where type = 'table'";
     }
+    std::string get_column_descriptions_query() const override
+    {
+        return "pragma table_info(:t)";
+    }
+    details::prepare_temp_type prepare_column_descriptions_statement(
+            details::prepare_type& prepare, std::string & table_name, soci::column_info& info) override;
     std::string create_column_type(data_type dt,
                                            int , int ) override
     {

src/backends/sqlite3/session.cpp

@@ -26,6 +26,64 @@ using namespace sqlite_api;
 
 namespace // anonymous
 {
+namespace soci
+{
+    // Overload of the column_info to work with the specific table structure of sqlite
+    struct sqlite_column_info final : public column_info { sqlite_column_info() = delete; }
+
+    template<>
+    struct type_conversion<sqlite_column_info>
+    {
+        typedef values base_type;
+        static void from_base(values const & v, indicator /* ind */, sqlite_column_info & ci)
+        {
+            ci.name = v.get<std::string>("name");
+            ci.length = 0;
+            ci.precision = 0;
+            ci.scale = 0;
+            ci.nullable = (v.get<std::string>("notnull") == "0");
+
+            std::string type_name = v.get<std::string>("type");
+            std::transform(type_name.begin(), type_name.end(), type_name.begin(), ::tolower);
+
+            if (type_name == "text" || type_name == "clob" ||
+                type_name.find("char") != std::string::npos)
+            {
+                ci.type = dt_string;
+            }
+            else if (type_name.find("int") != std::string::npos ||
+                    type_name.find("number") != std::string::npos ||
+                    type_name.find("numeric") != std::string::npos)
+            {
+                ci.type = dt_integer;
+            }
+            else if (type_name.find("double") != std::string::npos ||
+                    type_name.find("float") != std::string::npos ||
+                    type_name.find("real") != std::string::npos)
+            {
+                ci.type = dt_double;
+            }
+            else if (type_name.find("time") != std::string::npos ||
+                    type_name.find("date") != std::string::npos)
+            {
+                ci.type = dt_date;
+            }
+            else if (type_name.find("blob") != std::string::npos ||
+                    type_name.find("oid") != std::string::npos)
+            {
+                ci.type = dt_blob;
+            }
+            else if (type_name.find("xml") != std::string::npos)
+            {
+                ci.type = dt_xml;
+            }
+            else
+            {
+                ci.type = dt_string;
+            }
+        }
+    }
+} // !namesapce soci
 
 // Callback function use to construct the error message in the provided stream.
 //
@@ -328,3 +386,11 @@ sqlite3_blob_backend * sqlite3_session_backend::make_blob_backend()
 {
     return new sqlite3_blob_backend(*this);
 }
+
+details::prepare_temp_type prepare_column_descriptions_statement(
+        details::prepare_type& prepare, std::string & table_name, soci::column_info& info)
+{
+    soci::sqlite_column_info& sqlite_info = reinterpret_cast<soci::sqlite_column_info&>(info);
+    return prepare << get_column_descriptions_query(), soci::use(table_name, "t"), soci::into(info);
+
+}

src/core/session.cpp

@@ -471,6 +471,13 @@ details::prepare_temp_type session::prepare_column_descriptions(std::string & ta
     return prepare << backEnd_->get_column_descriptions_query(), use(table_name, "t");
 }
 
+details::prepare_temp_type session::prepare_column_descriptions(std::string & table_name, soci::column_info & info)
+{
+    ensureConnected(backEnd_);
+
+    return backEnd_->prepare_column_descriptions_statement(table_name, info);
+}
+
 ddl_type session::create_table(const std::string & tableName)
 {
     ddl_type ddl(*this);

tests/oracle/test-oracle.cpp

@@ -1116,7 +1116,7 @@ TEST_CASE("Oracle DDL with metadata", "[oracle][ddl]")
     bool j_found = false;
     bool other_found = false;
     soci::column_info ci;
-    soci::statement st1 = (sql.prepare_column_descriptions(ddl_t1), into(ci));
+    soci::statement st1 = sql.prepare_column_descriptions(ddl_t1, ci);
     st1.execute();
     while (st1.fetch())
     {
@@ -1194,7 +1194,7 @@ TEST_CASE("Oracle DDL with metadata", "[oracle][ddl]")
     bool k_found = false;
     bool big_found = false;
     other_found = false;
-    soci::statement st3 = (sql.prepare_column_descriptions(ddl_t1), into(ci));
+    soci::statement st3 = sql.prepare_column_descriptions(ddl_t1, ci);
     st3.execute();
     while (st3.fetch())
     {
@@ -1235,7 +1235,7 @@ TEST_CASE("Oracle DDL with metadata", "[oracle][ddl]")
     k_found = false;
     bool m_found = false;
     other_found = false;
-    soci::statement st4 = (sql.prepare_column_descriptions(ddl_t2), into(ci));
+    soci::statement st4 = sql.prepare_column_descriptions(ddl_t2, ci);
     st4.execute();
     while (st4.fetch())
     {

tests/postgresql/test-postgresql.cpp

@@ -774,7 +774,7 @@ TEST_CASE("PostgreSQL DDL with metadata", "[postgresql][ddl]")
     bool j_found = false;
     bool other_found = false;
     soci::column_info ci;
-    soci::statement st1 = (sql.prepare_column_descriptions(ddl_t1), into(ci));
+    soci::statement st1 = sql.prepare_column_descriptions(ddl_t1, ci);
     st1.execute();
     while (st1.fetch())
     {
@@ -852,7 +852,7 @@ TEST_CASE("PostgreSQL DDL with metadata", "[postgresql][ddl]")
     bool k_found = false;
     bool big_found = false;
     other_found = false;
-    soci::statement st3 = (sql.prepare_column_descriptions(ddl_t1), into(ci));
+    soci::statement st3 = sql.prepare_column_descriptions(ddl_t1, ci);
     st3.execute();
     while (st3.fetch())
     {
@@ -893,7 +893,7 @@ TEST_CASE("PostgreSQL DDL with metadata", "[postgresql][ddl]")
     k_found = false;
     bool m_found = false;
     other_found = false;
-    soci::statement st4 = (sql.prepare_column_descriptions(ddl_t2), into(ci));
+    soci::statement st4 = sql.prepare_column_descriptions(ddl_t2, ci);
     st4.execute();
     while (st4.fetch())
     {