Add query for column_info in sqlite3 backend

.gitignore

@@ -16,21 +16,31 @@ tmp
 
 # Files generated by CMake
 Makefile
+include/soci/soci-config.h
 src/core/soci_backends_config.h
 tests/odbc/test-access.dsn
 tests/odbc/test-mysql.dsn
+tests/odbc/test-mssql.dsn
+*.dir/
 
 # ... and the rest of CMake spam
 CMakeFiles/
 CMakeCache.txt
 CTestTestfile.cmake
 cmake_install.cmake
+src/core/SOCIConfig.cmake
+src/core/SOCIConfigVersion.cmake
 
 # Visual Studio / Visual Studio Code
 *.opensdf
 *.sdf
 *.suo
 /*.vs*
+*.vcxproj*
+SOCI.sln
+bin/
+lib/
+x64/
 
 # KDevelop
 *.kate-swp

include/soci/sqlite3/soci-sqlite3.h

@@ -307,6 +307,21 @@ 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 "select name as 'COLUMN_NAME',"
+            " 0 as 'CHARACTER_MAXIMUM_LENGTH',"
+            " 0 as 'NUMERIC_PRECISION',"
+            " case when type like '%real%' or type like '%float%' or type like '%double%' then 255 else 0 end as 'NUMERIC_SCALE',"
+            " case"
+                " when type like 'text'   or type like 'clob'     or type like '%char%'    then 'text'"
+                " when type like '%int%'  or type like '%number%' or type like '%numeric%' then 'integer'"
+                " when type like '%real%' or type like '%float%'  or type like '%double%'  then 'number'"
+                " else type"
+            " end as 'DATA_TYPE',"
+        " case when \"notnull\" = 0 then 'YES' else 'NO' end as 'IS_NULLABLE'"
+        " from (select name, lower(type) as type, \"notnull\" from pragma_table_info(:t))";
+    }
     std::string create_column_type(data_type dt,
                                            int , int ) override
     {

tests/sqlite3/test-sqlite3.cpp

@@ -413,6 +413,233 @@ TEST_CASE("SQLite long long", "[sqlite][longlong]")
     CHECK(v2 == v1);
 }
 
+// Test the DDL and metadata functionality
+TEST_CASE("SQLite DDL with metadata", "[sqlite][ddl]")
+{
+    if (sqlite3_libversion_number() < 3036000) {
+        if (sqlite3_libversion_number() < 3014000) {
+            WARN("SQLite requires at least version 3.14.0 for column description, detected " SQLITE_VERSION);
+        }
+        WARN("SQLite requires at least version 3.36.0 for drop column, detected " SQLITE_VERSION);
+        return;
+    }
+    soci::session sql(backEnd, connectString);
+
+    // note: prepare_column_descriptions expects l-value
+    std::string ddl_t1 = "DDL_T1";
+    std::string ddl_t2 = "DDL_T2";
+    std::string ddl_t3 = "DDL_T3";
+
+    // single-expression variant:
+    sql.create_table(ddl_t1).column("I", soci::dt_integer).column("J", soci::dt_integer);
+
+    // check whether this table was created:
+
+    bool ddl_t1_found = false;
+    bool ddl_t2_found = false;
+    bool ddl_t3_found = false;
+    std::string table_name;
+    soci::statement st = (sql.prepare_table_names(), into(table_name));
+    st.execute();
+    while (st.fetch())
+    {
+        if (table_name == ddl_t1) { ddl_t1_found = true; }
+        if (table_name == ddl_t2) { ddl_t2_found = true; }
+        if (table_name == ddl_t3) { ddl_t3_found = true; }
+    }
+
+    CHECK(ddl_t1_found);
+    CHECK(ddl_t2_found == false);
+    CHECK(ddl_t3_found == false);
+
+    // check whether ddl_t1 has the right structure:
+
+    bool i_found = false;
+    bool j_found = false;
+    bool other_found = false;
+    soci::column_info ci;
+    soci::statement st1 = (sql.prepare_column_descriptions(ddl_t1), into(ci));
+    st1.execute();
+    while (st1.fetch())
+    {
+        if (ci.name == "I")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable);
+            i_found = true;
+        }
+        else if (ci.name == "J")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable);
+            j_found = true;
+        }
+        else
+        {
+            other_found = true;
+        }
+    }
+
+    CHECK(i_found);
+    CHECK(j_found);
+    CHECK(other_found == false);
+
+    // two more tables:
+
+    // separately defined columns:
+    // (note: statement is executed when ddl object goes out of scope)
+    {
+        soci::ddl_type ddl = sql.create_table(ddl_t2);
+        ddl.column("I", soci::dt_integer);
+        ddl.column("J", soci::dt_integer);
+        ddl.column("K", soci::dt_integer)("not null");
+        ddl.primary_key("t2_pk", "J");
+    }
+
+    sql.add_column(ddl_t1, "K", soci::dt_integer);
+    sql.add_column(ddl_t1, "BIG", soci::dt_string, 0); // "unlimited" length -> CLOB
+    sql.drop_column(ddl_t1, "I");
+
+    // or with constraint as in t2:
+    sql.add_column(ddl_t2, "M", soci::dt_integer)("not null");
+
+    // third table with a foreign key to the second one
+    {
+        soci::ddl_type ddl = sql.create_table(ddl_t3);
+        ddl.column("X", soci::dt_integer);
+        ddl.column("Y", soci::dt_integer);
+        ddl.foreign_key("t3_fk", "X", ddl_t2, "J");
+    }
+
+    // check if all tables were created:
+
+    ddl_t1_found = false;
+    ddl_t2_found = false;
+    ddl_t3_found = false;
+    soci::statement st2 = (sql.prepare_table_names(), into(table_name));
+    st2.execute();
+    while (st2.fetch())
+    {
+        if (table_name == ddl_t1) { ddl_t1_found = true; }
+        if (table_name == ddl_t2) { ddl_t2_found = true; }
+        if (table_name == ddl_t3) { ddl_t3_found = true; }
+    }
+
+    CHECK(ddl_t1_found);
+    CHECK(ddl_t2_found);
+    CHECK(ddl_t3_found);
+
+    // check if ddl_t1 has the right structure (it was altered):
+
+    i_found = false;
+    j_found = false;
+    bool k_found = false;
+    bool big_found = false;
+    other_found = false;
+    soci::statement st3 = (sql.prepare_column_descriptions(ddl_t1), into(ci));
+    st3.execute();
+    while (st3.fetch())
+    {
+        if (ci.name == "J")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable);
+            j_found = true;
+        }
+        else if (ci.name == "K")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable);
+            k_found = true;
+        }
+        else if (ci.name == "BIG")
+        {
+            CHECK(ci.type == soci::dt_string);
+            CHECK(ci.precision == 0); // "unlimited" for strings
+            big_found = true;
+        }
+        else
+        {
+            other_found = true;
+        }
+    }
+
+    CHECK(i_found == false);
+    CHECK(j_found);
+    CHECK(k_found);
+    CHECK(big_found);
+    CHECK(other_found == false);
+
+    // check if ddl_t2 has the right structure:
+
+    i_found = false;
+    j_found = false;
+    k_found = false;
+    bool m_found = false;
+    other_found = false;
+    soci::statement st4 = (sql.prepare_column_descriptions(ddl_t2), into(ci));
+    st4.execute();
+    while (st4.fetch())
+    {
+        if (ci.name == "I")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable);
+            i_found = true;
+        }
+        else if (ci.name == "J")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable == true); // primary key -> SQLite default behavior
+            j_found = true;
+        }
+        else if (ci.name == "K")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable == false);
+            k_found = true;
+        }
+        else if (ci.name == "M")
+        {
+            CHECK(ci.type == soci::dt_integer);
+            CHECK(ci.nullable == false);
+            m_found = true;
+        }
+        else
+        {
+            other_found = true;
+        }
+    }
+
+    CHECK(i_found);
+    CHECK(j_found);
+    CHECK(k_found);
+    CHECK(m_found);
+    CHECK(other_found == false);
+
+    sql.drop_table(ddl_t1);
+    sql.drop_table(ddl_t3); // note: this must be dropped before ddl_t2
+    sql.drop_table(ddl_t2);
+
+    // check if all tables were dropped:
+
+    ddl_t1_found = false;
+    ddl_t2_found = false;
+    ddl_t3_found = false;
+    st2 = (sql.prepare_table_names(), into(table_name));
+    st2.execute();
+    while (st2.fetch())
+    {
+        if (table_name == ddl_t1) { ddl_t1_found = true; }
+        if (table_name == ddl_t2) { ddl_t2_found = true; }
+        if (table_name == ddl_t3) { ddl_t3_found = true; }
+    }
+
+    CHECK(ddl_t1_found == false);
+    CHECK(ddl_t2_found == false);
+    CHECK(ddl_t3_found == false);
+}
+
 TEST_CASE("SQLite vector long long", "[sqlite][vector][longlong]")
 {
     soci::session sql(backEnd, connectString);