func()

in pq/writer.go [269:344]

• 55 lines of code
• 11 McCabe index (conditional complexity)

func (w *Writer) doFlush() (pages, allocated uint, err error) {
	start, end, pages := w.state.buf.Pages()
	if start == nil || start == end {
		return 0, 0, nil
	}

	traceln("writer flush", w.state.activeEventCount)
	tracef("flush page range: start=%p, end=%p, n=%v\n", start, end, pages)

	// unallocated points to first page in list that must be allocated.  All
	// pages between unallocated and end require a new page to be allocated.
	var unallocated *page
	allocated = pages
	for current := start; current != end; current = current.Next {
		tracef("check page assigned: %p (%v)\n", current, current.Assigned())

		if !current.Assigned() {
			unallocated = current
			break
		}
		allocated--
	}

	tracef("start allocating pages from %p (n=%v)\n", unallocated, allocated)

	tx, txErr := w.accessor.BeginWrite()
	if txErr != nil {
		return pages, allocated, w.errWrap("", txErr)
	}
	defer tx.Close()

	rootPage, queueHdr, err := w.accessor.LoadRootPage(tx)
	if err != nil {
		return pages, allocated, w.errWrap("", err)
	}

	traceQueueHeader(queueHdr)

	ok := false
	allocN, txErr := allocatePages(tx, unallocated, end)
	if txErr != nil {
		return pages, allocated, w.errWrap("", txErr)
	}

	traceln("allocated pages:", allocN)
	invariant.Checkf(allocN == allocated, "allocation counter mismatch (expected=%v, actual=%v)", allocated, allocN)

	linkPages(start, end)
	defer cleanup.IfNot(&ok, func() { unassignPages(unallocated, end) })

	traceln("write queue pages")
	last, txErr := flushPages(tx, start, end)
	if txErr != nil {
		return pages, allocated, w.errWrap("", txErr)
	}

	// update queue root
	w.updateRootHdr(queueHdr, start, last, allocN)
	rootPage.MarkDirty()

	txErr = tx.Commit()
	if txErr != nil {
		return pages, allocated, w.errWrap("", txErr)
	}

	// mark write as success -> no error-cleanup required
	ok = true

	// remove dirty flag from all published pages
	for current := start; current != end; current = current.Next {
		current.UnmarkDirty()
	}

	w.state.buf.Reset(last)
	return pages, allocated, nil
}