MappedRegion.h File Reference

File-backed memory region with two interchangeable backends. More...

#include <cerrno>
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <stdexcept>
#include <fcntl.h>
#include <unistd.h>
#include "provsql_config.h"
#include <sys/mman.h>

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Classes
class	MappedRegion

Detailed Description

File-backed memory region with two interchangeable backends.

A MappedRegion owns a backing file and a base pointer to length() bytes of it, with map() / remap() / sync() / close(). It is the single storage primitive under MMappedVector and MMappedUUIDHashTable.

Multi-process build: the region is a shared (MAP_SHARED) mmap of the file. The kernel keeps the mapping coherent across the backends and the worker and flushes dirty pages, so a backend's writes are visible to the others through the same file.

Single-process build (PROVSQL_INPROCESS_STORE): the region is a heap buffer loaded from the file on map() and written back explicitly on sync() / close(). Emscripten does not support MAP_SHARED write-back, and with a single process a shared mapping has no purpose; the file still lives under $PGDATA, so PGlite persists it. Write-back timing is the caller's responsibility (the store registers an on_proc_exit hook so a backend flushes before it exits).

Definition in file MappedRegion.h.