branches/zip: Allow dirty blocks to be relocated. Allow a transition

to BUF_BLOCK_ZIP_DIRTY (discarding the uncompressed page corresponding
to a modified compressed page that has not been flushed to disk).

buf_page_can_relocate(): New function, modelled after
buf_flush_ready_for_replace().

buf_LRU_free_block(): Allow the transition to BUF_BLOCK_ZIP_DIRTY.

buf_flush_insert_into_flush_list(): Make the prototype public.

buf_buddy_relocate(): Remove an unnecessary switch statement.
Use buf_page_can_relocate() instead of buf_flush_ready_for_replace().

buf_page_peek(): Made UNIV_INLINE.

Document UNIV_ZIP_DEBUG.

buf/buf0buddy.c

@@ -400,26 +400,13 @@ buf_buddy_relocate(
 
 		mutex_enter(mutex);
 
-		if (buf_flush_ready_for_replace(bpage)) {
-			switch (buf_page_get_state(bpage)) {
-			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:
-				ut_error;
-				break;
-
-			case BUF_BLOCK_ZIP_PAGE:
-			case BUF_BLOCK_ZIP_DIRTY:
-			case BUF_BLOCK_FILE_PAGE:
-				/* Relocate the compressed page. */
-				ut_a(bpage->zip.data == src);
-				memcpy(dst, src, size);
-				bpage->zip.data = dst;
-				mutex_exit(mutex);
-				return(TRUE);
-			}
+		if (buf_page_can_relocate(bpage)) {
+			/* Relocate the compressed page. */
+			ut_a(bpage->zip.data == src);
+			memcpy(dst, src, size);
+			bpage->zip.data = dst;
+			mutex_exit(mutex);
+			return(TRUE);
 		}
 
 		mutex_exit(mutex);
@@ -444,7 +431,7 @@ buf_buddy_relocate(
 		case BUF_BLOCK_ZIP_PAGE:
 			mutex_enter(&buf_pool->zip_mutex);
 
-			if (buf_flush_ready_for_replace(bpage)) {
+			if (buf_page_can_relocate(bpage)) {
 				buf_page_t*	dpage	= (buf_page_t*) dst;
 				buf_page_t*	b;
 

buf/buf0buf.c

@@ -1387,27 +1387,6 @@ buf_page_peek_if_search_hashed(
 	return(is_hashed);
 }
 
-/************************************************************************
-Returns TRUE if the page can be found in the buffer pool hash table. NOTE
-that it is possible that the page is not yet read from disk, though. */
-
-ibool
-buf_page_peek(
-/*==========*/
-			/* out: TRUE if found from page hash table,
-			NOTE that the page is not necessarily yet read
-			from disk! */
-	ulint	space,	/* in: space id */
-	ulint	offset)	/* in: page number */
-{
-	if (buf_page_peek_block(space, offset)) {
-
-		return(TRUE);
-	}
-
-	return(FALSE);
-}
-
 #ifdef UNIV_DEBUG_FILE_ACCESSES
 /************************************************************************
 Sets file_page_was_freed TRUE if the page is found in the buffer pool.

buf/buf0lru.c

@@ -892,11 +892,18 @@ buf_LRU_free_block(
 	ut_ad(buf_page_in_file(bpage));
 	ut_ad(bpage->in_LRU_list);
 
-	if (!buf_flush_ready_for_replace(bpage)) {
+	if (!buf_page_can_relocate(bpage)) {
 
 		return(FALSE);
 	}
 
+	if (bpage->oldest_modification
+	    && (zip || buf_page_get_state(bpage) == BUF_BLOCK_FILE_PAGE)) {
+
+		/* Do not completely free dirty blocks. */
+		return(FALSE);
+	}
+
 #ifdef UNIV_DEBUG
 	if (buf_debug_prints) {
 		fprintf(stderr, "Putting space %lu page %lu to free list\n",
@@ -926,7 +933,9 @@ buf_LRU_free_block(
 				ulint	fold;
 
 				memcpy(b, bpage, sizeof *b);
-				b->state = BUF_BLOCK_ZIP_PAGE;
+				b->state = b->oldest_modification
+					? BUF_BLOCK_ZIP_DIRTY
+					: BUF_BLOCK_ZIP_PAGE;
 
 				fold = buf_page_address_fold(b->space,
 							     b->offset);
@@ -936,7 +945,11 @@ buf_LRU_free_block(
 
 				buf_LRU_add_block_low(b, TRUE);
 
-				buf_LRU_insert_zip_clean(b);
+				if (b->state == BUF_BLOCK_ZIP_PAGE) {
+					buf_LRU_insert_zip_clean(b);
+				} else {
+					buf_flush_insert_into_flush_list(b);
+				}
 
 				mutex_enter(block_mutex);
 

include/buf0buf.h

@@ -288,7 +288,7 @@ buf_page_make_young(
 /************************************************************************
 Returns TRUE if the page can be found in the buffer pool hash table. NOTE
 that it is possible that the page is not yet read from disk, though. */
-
+UNIV_INLINE
 ibool
 buf_page_peek(
 /*==========*/
@@ -702,6 +702,16 @@ buf_block_set_io_fix(
 	buf_block_t*	block,	/* in/out: control block */
 	enum buf_io_fix	io_fix);/* in: io_fix state */
 
+/************************************************************************
+Determine if a buffer block can be relocated in memory.  The block
+can be dirty, but it must not be I/O-fixed or bufferfixed. */
+UNIV_INLINE
+ibool
+buf_page_can_relocate(
+/*==================*/
+	const buf_page_t*	bpage)	/* control block being relocated */
+	__attribute__((const));
+
 /*************************************************************************
 Determine if a block has been flagged old. */
 UNIV_INLINE

include/buf0buf.ic

@@ -11,6 +11,22 @@ Created 11/5/1995 Heikki Tuuri
 #include "buf0rea.h"
 #include "mtr0mtr.h"
 
+/************************************************************************
+Returns TRUE if the page can be found in the buffer pool hash table. NOTE
+that it is possible that the page is not yet read from disk, though. */
+UNIV_INLINE
+ibool
+buf_page_peek(
+/*==========*/
+			/* out: TRUE if found from page hash table,
+			NOTE that the page is not necessarily yet read
+			from disk! */
+	ulint	space,	/* in: space id */
+	ulint	offset)	/* in: page number */
+{
+	return(buf_page_peek_block(space, offset) != NULL);
+}
+
 /************************************************************************
 Reads the freed_page_clock of a buffer block. */
 UNIV_INLINE
@@ -386,6 +402,26 @@ buf_block_set_io_fix(
 	buf_page_set_io_fix(&block->page, io_fix);
 }
 
+/************************************************************************
+Determine if a buffer block can be relocated in memory.  The block
+can be dirty, but it must not be I/O-fixed or bufferfixed. */
+UNIV_INLINE
+ibool
+buf_page_can_relocate(
+/*==================*/
+	const buf_page_t*	bpage)	/* control block being relocated */
+{
+#ifdef UNIV_SYNC_DEBUG
+	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(mutex_own(buf_page_get_mutex((buf_page_t*) bpage)));
+#endif /* UNIV_SYNC_DEBUG */
+	ut_ad(buf_page_in_file(bpage));
+	ut_ad(bpage->in_LRU_list);
+
+	return(buf_page_get_io_fix(bpage) == BUF_IO_NONE
+	       && bpage->buf_fix_count == 0);
+}
+
 /*************************************************************************
 Determine if a block has been flagged old. */
 UNIV_INLINE

include/buf0flu.h

@@ -14,6 +14,13 @@ Created 11/5/1995 Heikki Tuuri
 #include "ut0byte.h"
 #include "mtr0types.h"
 
+/************************************************************************
+Inserts a modified block into the flush list. */
+
+void
+buf_flush_insert_into_flush_list(
+/*=============================*/
+	buf_page_t*	bpage);	/* in: block which is modified */
 /************************************************************************
 Remove a block from the flush list of modified blocks. */
 
@@ -102,6 +109,7 @@ buf_flush_recv_note_modification(
 /************************************************************************
 Returns TRUE if the file page block is immediately suitable for replacement,
 i.e., transition FILE_PAGE => NOT_USED allowed. */
+
 ibool
 buf_flush_ready_for_replace(
 /*========================*/

include/buf0flu.ic

@@ -9,13 +9,6 @@ Created 11/5/1995 Heikki Tuuri
 #include "buf0buf.h"
 #include "mtr0mtr.h"
 
-/************************************************************************
-Inserts a modified block into the flush list. */
-
-void
-buf_flush_insert_into_flush_list(
-/*=============================*/
-	buf_page_t*	bpage);	/* in: block which is modified */
 /************************************************************************
 Inserts a modified block into the flush list in the right sorted position.
 This function is used by recovery, because there the modifications do not

include/univ.i

@@ -103,7 +103,8 @@ operations (very slow); also UNIV_DEBUG must be defined */
 						in sync0sync.c */
 #define UNIV_BTR_PRINT				/* enable functions for
 						printing B-trees */
-#define UNIV_ZIP_DEBUG
+#define UNIV_ZIP_DEBUG				/* extensive consistency checks
+						for compressed pages */
 #endif
 
 #define UNIV_BTR_DEBUG				/* check B-tree links */