branches/zip: When retrieving compressed BLOBs, avoid allocating

uncompressed page frames.

buf_page_get_zip(), buf_page_release_zip(): New functions, used
by btr_copy_zblob_prefix().

btr_copy_zblob_prefix(): Do not call inflateEnd().

btr/btr0cur.c

@@ -4312,33 +4312,35 @@ btr_copy_zblob_prefix(
 	ut_ad(space_id);
 
 	for (;;) {
-		mtr_t		mtr;
-		buf_block_t*	block;
-		page_t*		page;
+		buf_page_t*	bpage;
 		int		err;
 		ulint		next_page_no;
 
-		mtr_start(&mtr);
+		bpage = buf_page_get_zip(space_id, zip_size, page_no);
 
-		block = buf_page_get(space_id, zip_size, page_no,
-				     RW_S_LATCH, &mtr);
-#ifdef UNIV_SYNC_DEBUG
-		buf_block_dbg_add_level(block, SYNC_EXTERN_STORAGE);
-#endif /* UNIV_SYNC_DEBUG */
-		page = buf_block_get_frame(block);
+		if (UNIV_UNLIKELY(!bpage)) {
+			ut_print_timestamp(stderr);
+			fprintf(stderr,
+				"  InnoDB: Cannot load"
+				" compressed BLOB"
+				" page %lu space %lu\n",
+				(ulong) page_no, (ulong) space_id);
+			return;
+		}
 
-		if (UNIV_UNLIKELY(fil_page_get_type(page)
+		if (UNIV_UNLIKELY(fil_page_get_type(bpage->zip.data)
 				  != FIL_PAGE_TYPE_ZBLOB)) {
 			ut_print_timestamp(stderr);
 			fprintf(stderr,
 				"  InnoDB: Unknown type %lu of"
 				" compressed BLOB"
 				" page %lu space %lu\n",
-				(ulong) fil_page_get_type(page),
+				(ulong) fil_page_get_type(bpage->zip.data),
 				(ulong) page_no, (ulong) space_id);
+			goto end_of_blob;
 		}
 
-		next_page_no = mach_read_from_4(page + offset);
+		next_page_no = mach_read_from_4(bpage->zip.data + offset);
 
 		if (UNIV_LIKELY(offset == FIL_PAGE_NEXT)) {
 			/* When the BLOB begins at page header,
@@ -4349,7 +4351,7 @@ btr_copy_zblob_prefix(
 			offset += 4;
 		}
 
-		d_stream->next_in = page + offset;
+		d_stream->next_in = bpage->zip.data + offset;
 		d_stream->avail_in = zip_size - offset;
 
 		err = inflate(d_stream, Z_NO_FLUSH);
@@ -4388,19 +4390,21 @@ inflate_error:
 					(ulong) space_id);
 			} else {
 				err = inflate(d_stream, Z_FINISH);
-				if (UNIV_UNLIKELY
-				    (err != Z_STREAM_END)) {
+				switch (err) {
+				case Z_STREAM_END:
+				case Z_BUF_ERROR:
+					break;
+				default:
 					goto inflate_error;
 				}
 			}
 
 end_of_blob:
-			mtr_commit(&mtr);
-			inflateEnd(d_stream);
+			buf_page_release_zip(bpage);
 			return;
 		}
 
-		mtr_commit(&mtr);
+		buf_page_release_zip(bpage);
 
 		/* On other BLOB pages except the first
 		the BLOB header always is at the page header: */
@@ -4447,6 +4451,7 @@ btr_copy_externally_stored_field_prefix_low(
 
 		btr_copy_zblob_prefix(&d_stream, zip_size,
 				      space_id, page_no, offset);
+		inflateEnd(&d_stream);
 		return(d_stream.total_out);
 	} else {
 		return(btr_copy_blob_prefix(buf, len, space_id,

buf/buf0buf.c

@@ -1458,6 +1458,126 @@ buf_page_reset_file_page_was_freed(
 }
 #endif /* UNIV_DEBUG_FILE_ACCESSES */
 
+/************************************************************************
+Get read access to a compressed page (usually FIL_PAGE_TYPE_ZBLOB). */
+
+buf_page_t*
+buf_page_get_zip(
+/*=============*/
+				/* out: pointer to the block */
+	ulint		space,	/* in: space id */
+	ulint		zip_size,/* in: compressed page size */
+	ulint		offset)	/* in: page number */
+{
+	buf_page_t*	bpage;
+	mutex_t*	block_mutex;
+	ibool		must_read;
+
+#ifndef UNIV_LOG_DEBUG
+	ut_ad(!ibuf_inside());
+#endif
+	buf_pool->n_page_gets++;
+
+	for (;;) {
+		mutex_enter_fast(&buf_pool->mutex);
+lookup:
+		bpage = buf_page_hash_get(space, offset);
+		if (bpage) {
+			break;
+		}
+
+		/* Page not in buf_pool: needs to be read from file */
+
+		mutex_exit(&buf_pool->mutex);
+
+		buf_read_page(space, zip_size, offset);
+
+#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
+		ut_a(++buf_dbg_counter % 37 || buf_validate());
+#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */
+	}
+
+	if (UNIV_UNLIKELY(!bpage->zip.data)) {
+		/* There is no compressed page. */
+		mutex_exit(&buf_pool->mutex);
+		return(NULL);
+	}
+
+	block_mutex = buf_page_get_mutex(bpage);
+	mutex_enter(block_mutex);
+
+	switch (buf_page_get_state(bpage)) {
+	case BUF_BLOCK_NOT_USED:
+	case BUF_BLOCK_READY_FOR_USE:
+	case BUF_BLOCK_MEMORY:
+	case BUF_BLOCK_REMOVE_HASH:
+	case BUF_BLOCK_ZIP_FREE:
+		ut_error;
+		break;
+	case BUF_BLOCK_ZIP_PAGE:
+	case BUF_BLOCK_ZIP_DIRTY:
+		bpage->buf_fix_count++;
+		break;
+	case BUF_BLOCK_FILE_PAGE:
+		/* Discard the uncompressed page frame if possible. */
+		if (buf_LRU_free_block(bpage, FALSE)) {
+
+			mutex_exit(block_mutex);
+			goto lookup;
+		}
+
+		buf_block_buf_fix_inc((buf_block_t*) bpage,
+				      __FILE__, __LINE__);
+		break;
+	}
+
+	must_read = buf_page_get_io_fix(bpage) == BUF_IO_READ;
+
+	mutex_exit(&buf_pool->mutex);
+
+	buf_page_set_accessed(bpage, TRUE);
+
+	mutex_exit(block_mutex);
+
+	buf_block_make_young(bpage);
+
+#ifdef UNIV_DEBUG_FILE_ACCESSES
+	ut_a(!bpage->file_page_was_freed);
+#endif
+
+#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
+	ut_a(++buf_dbg_counter % 5771 || buf_validate());
+	ut_a(bpage->buf_fix_count > 0);
+	ut_a(buf_page_in_file(bpage));
+#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */
+
+	if (must_read) {
+		/* Let us wait until the read operation
+		completes */
+
+		for (;;) {
+			enum buf_io_fix	io_fix;
+
+			mutex_enter(block_mutex);
+			io_fix = buf_page_get_io_fix(bpage);
+			mutex_exit(block_mutex);
+
+			if (io_fix == BUF_IO_READ) {
+
+				os_thread_sleep(WAIT_FOR_READ);
+			} else {
+				break;
+			}
+		}
+	}
+
+#ifdef UNIV_IBUF_DEBUG
+	ut_a(ibuf_count_get(buf_page_get_space(bpage),
+			    buf_page_get_page_no(bpage)) == 0);
+#endif
+	return(bpage);
+}
+
 /************************************************************************
 This is the general function used to get access to a database page. */
 

include/buf0buf.h

@@ -223,6 +223,18 @@ buf_page_get_known_nowait(
 	ulint		line,	/* in: line where called */
 	mtr_t*		mtr);	/* in: mini-transaction */
 /************************************************************************
+Get read access to a compressed page (usually FIL_PAGE_TYPE_ZBLOB).
+The page must be released with buf_page_release_zip(). */
+
+buf_page_t*
+buf_page_get_zip(
+/*=============*/
+				/* out: pointer to the block,
+				or NULL if not compressed */
+	ulint		space,	/* in: space id */
+	ulint		zip_size,/* in: compressed page size */
+	ulint		offset);/* in: page number */
+/************************************************************************
 This is the general function used to get access to a database page. */
 
 buf_block_t*
@@ -270,6 +282,13 @@ buf_page_init_for_backup_restore(
 	buf_block_t*	block);	/* in: block to init */
 #endif /* UNIV_HOTBACKUP */
 /************************************************************************
+Releases a compressed-only page acquired with buf_page_get_zip(). */
+UNIV_INLINE
+void
+buf_page_release_zip(
+/*=================*/
+	buf_page_t*	bpage);		/* in: buffer block */
+/************************************************************************
 Decrements the bufferfix count of a buffer control block and releases
 a latch, if specified. */
 UNIV_INLINE

include/buf0buf.ic

@@ -954,6 +954,46 @@ buf_page_get_release_on_io(
 	return(NULL);
 }
 
+/************************************************************************
+Releases a compressed-only page acquired with buf_page_get_zip(). */
+UNIV_INLINE
+void
+buf_page_release_zip(
+/*=================*/
+	buf_page_t*	bpage)		/* in: buffer block */
+{
+	buf_block_t*	block;
+
+	ut_ad(bpage);
+	ut_a(bpage->buf_fix_count > 0);
+
+	switch (buf_page_get_state(bpage)) {
+	case BUF_BLOCK_ZIP_PAGE:
+	case BUF_BLOCK_ZIP_DIRTY:
+		mutex_enter(&buf_pool->zip_mutex);
+		bpage->buf_fix_count--;
+		mutex_exit(&buf_pool->zip_mutex);
+		return;
+	case BUF_BLOCK_FILE_PAGE:
+		block = (buf_block_t*) bpage;
+		mutex_enter(&block->mutex);
+#ifdef UNIV_SYNC_DEBUG
+		rw_lock_s_unlock(&block->debug_latch);
+#endif
+		bpage->buf_fix_count--;
+		mutex_exit(&block->mutex);
+		return;
+	case BUF_BLOCK_ZIP_FREE:
+	case BUF_BLOCK_NOT_USED:
+	case BUF_BLOCK_READY_FOR_USE:
+	case BUF_BLOCK_MEMORY:
+	case BUF_BLOCK_REMOVE_HASH:
+		break;
+	}
+
+	ut_error;
+}
+
 /************************************************************************
 Decrements the bufferfix count of a buffer control block and releases
 a latch, if specified. */