helpers.h

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#ifndef cetlib_sqlite_helpers_h
#define cetlib_sqlite_helpers_h

// ====================================================================
// These are general utilities for interacting with a database and any
// tables therein.
// ====================================================================

#include "cetlib/sqlite/column.h"
#include "cetlib/sqlite/create_table.h"
#include "cetlib/sqlite/exec.h"

#include "sqlite3.h"

#include <string>

using namespace std::string_literals;

namespace cet::sqlite {

  std::string assembleNoLockURI(std::string const& filename);
  bool hasTableWithSchema(sqlite3* db,
                          std::string const& tablename,
                          std::string expectedSchema);
  unsigned nrows(sqlite3* db, std::string const& tablename);

  void delete_from(sqlite3* db, std::string const& tablename);
  void drop_table(sqlite3* db, std::string const& tablename);
  void drop_table_if_exists(sqlite3* db, std::string const& tablename);

  // Could arguably go in detail namespace due to obscurity of
  // permissive_column.
  template <typename... Args>
  void createTableIfNeeded(sqlite3* db,
                           bool const delete_contents,
                           std::string const& tablename,
                           permissive_column<Args> const&... cols);

} // namespace cet::sqlite

//====================================================
// Implementation below

template <typename... Args>
void
cet::sqlite::createTableIfNeeded(sqlite3* db,
                                 bool const delete_contents,
                                 std::string const& tablename,
                                 permissive_column<Args> const&... cols)
{
  auto const& sqlddl = detail::create_table_ddl(tablename, cols...);
  if (hasTableWithSchema(db, tablename, sqlddl)) {
    if (delete_contents) {
      delete_from(db, tablename); // Prefer drop_table, but failure-to-prepare
                                  // exception ends up being thrown.
    }
  } else {
    exec(db, sqlddl);
  }
}

#endif /* cetlib_sqlite_helpers_h */

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