diff --git a/src/backend/access/heap/tuptoaster.c b/src/backend/access/heap/tuptoaster.c
index b9691a5..0fc5d5a 100644
--- a/src/backend/access/heap/tuptoaster.c
+++ b/src/backend/access/heap/tuptoaster.c
@@ -46,32 +46,12 @@
 
 #undef TOAST_DEBUG
 
-/*
- *	The information at the start of the compressed toast data.
- */
-typedef struct toast_compress_header
-{
-	int32		vl_len_;		/* varlena header (do not touch directly!) */
-	int32		rawsize;
-} toast_compress_header;
-
-/*
- * Utilities for manipulation of header information for compressed
- * toast entries.
- */
-#define TOAST_COMPRESS_HDRSZ		((int32) sizeof(toast_compress_header))
-#define TOAST_COMPRESS_RAWSIZE(ptr) (((toast_compress_header *) (ptr))->rawsize)
-#define TOAST_COMPRESS_RAWDATA(ptr) \
-	(((char *) (ptr)) + TOAST_COMPRESS_HDRSZ)
-#define TOAST_COMPRESS_SET_RAWSIZE(ptr, len) \
-	(((toast_compress_header *) (ptr))->rawsize = (len))
 
 static void toast_delete_datum(Relation rel, Datum value);
 static Datum toast_save_datum(Relation rel, Datum value,
 				 struct varlena * oldexternal, int options);
 static bool toastrel_valueid_exists(Relation toastrel, Oid valueid);
 static bool toastid_valueid_exists(Oid toastrelid, Oid valueid);
-static struct varlena *toast_fetch_datum(struct varlena * attr);
 static struct varlena *toast_fetch_datum_slice(struct varlena * attr,
 						int32 sliceoffset, int32 length);
 static struct varlena *toast_decompress_datum(struct varlena * attr);
@@ -1792,7 +1772,7 @@ toastid_valueid_exists(Oid toastrelid, Oid valueid)
  *	in the toast relation
  * ----------
  */
-static struct varlena *
+struct varlena *
 toast_fetch_datum(struct varlena * attr)
 {
 	Relation	toastrel;
@@ -2205,12 +2185,33 @@ toast_decompress_datum(struct varlena * attr)
 	if (pglz_decompress(TOAST_COMPRESS_RAWDATA(attr),
 						VARSIZE(attr) - TOAST_COMPRESS_HDRSZ,
 						VARDATA(result),
-						TOAST_COMPRESS_RAWSIZE(attr)) < 0)
+						TOAST_COMPRESS_RAWSIZE(attr),
+						NULL) < 0)
 		elog(ERROR, "compressed data is corrupted");
 
 	return result;
 }
 
+/* ----------
+ * toast_decompress_datum_partial -
+ *
+ * Decompress a compressed version of a varlena datum partially
+ */
+int
+toast_decompress_datum_partial(struct varlena *source,
+	struct varlena *dest,
+	PGLZ_DecompressState *state,
+	int32 until)
+{
+	Assert(VARATT_IS_COMPRESSED(source));
+
+	state->until = until;
+	return pglz_decompress(TOAST_COMPRESS_RAWDATA(source),
+						VARSIZE(source) - TOAST_COMPRESS_HDRSZ,
+						VARDATA(dest),
+						TOAST_COMPRESS_RAWSIZE(source),
+						state);
+}
 
 /* ----------
  * toast_open_indexes
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 37cf9de..a1642ed 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -1309,7 +1309,7 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
 	{
 		/* If a backup block image is compressed, decompress it */
 		if (pglz_decompress(ptr, bkpb->bimg_len, tmp,
-							BLCKSZ - bkpb->hole_length) < 0)
+							BLCKSZ - bkpb->hole_length, NULL) < 0)
 		{
 			report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
 								  (uint32) (record->ReadRecPtr >> 32),
diff --git a/src/common/pg_lzcompress.c b/src/common/pg_lzcompress.c
index 447a043..df5e169 100644
--- a/src/common/pg_lzcompress.c
+++ b/src/common/pg_lzcompress.c
@@ -680,18 +680,30 @@ pglz_compress(const char *source, int32 slen, char *dest,
  */
 int32
 pglz_decompress(const char *source, int32 slen, char *dest,
-				int32 rawsize)
+				int32 rawsize, PGLZ_DecompressState *state)
 {
-	const unsigned char *sp;
+	unsigned char *sp;
 	const unsigned char *srcend;
 	unsigned char *dp;
 	unsigned char *destend;
+	bool last_block = true;
 
-	sp = (const unsigned char *) source;
+	sp = (unsigned char *) source;
 	srcend = ((const unsigned char *) source) + slen;
 	dp = (unsigned char *) dest;
 	destend = dp + rawsize;
 
+	if (state != NULL)
+	{
+		last_block = (state->until >= rawsize);
+		sp += state->sp;
+		dp += state->dp;
+
+		Assert(sp <= srcend);
+		Assert(dp <= destend);
+		destend = last_block ? destend: ((unsigned char *) dest) + state->until;
+	}
+
 	while (sp < srcend && dp < destend)
 	{
 		/*
@@ -728,7 +740,7 @@ pglz_decompress(const char *source, int32 slen, char *dest,
 				 * don't simply put the elog inside the loop since that will
 				 * probably interfere with optimization.
 				 */
-				if (dp + len > destend)
+				if (last_block && (dp + len > destend))
 				{
 					dp += len;
 					break;
@@ -752,7 +764,7 @@ pglz_decompress(const char *source, int32 slen, char *dest,
 				 * An unset control bit means LITERAL BYTE. So we just copy
 				 * one from INPUT to OUTPUT.
 				 */
-				if (dp >= destend)		/* check for buffer overrun */
+				if (last_block && dp >= destend)		/* check for buffer overrun */
 					break;		/* do not clobber memory */
 
 				*dp++ = *sp++;
@@ -765,14 +777,22 @@ pglz_decompress(const char *source, int32 slen, char *dest,
 		}
 	}
 
-	/*
-	 * Check we decompressed the right amount.
-	 */
-	if (dp != destend || sp != srcend)
-		return -1;
+	if (!last_block && state != NULL)
+	{
+		state->sp = sp - (unsigned char *) source;
+		state->dp = dp - (unsigned char *) dest;
+	}
+	else
+	{
+		/*
+		 * Check we decompressed the right amount.
+		 */
+		if (dp != destend || sp != srcend)
+			return -1;
+	}
 
 	/*
 	 * That's it.
 	 */
-	return rawsize;
+	return dp - (unsigned char *)dest;
 }
diff --git a/src/include/access/tuptoaster.h b/src/include/access/tuptoaster.h
index 77f637e..5248d73 100644
--- a/src/include/access/tuptoaster.h
+++ b/src/include/access/tuptoaster.h
@@ -14,6 +14,7 @@
 #define TUPTOASTER_H
 
 #include "access/htup_details.h"
+#include "common/pg_lzcompress.h"
 #include "storage/lockdefs.h"
 #include "utils/relcache.h"
 
@@ -102,6 +103,26 @@
 #define INDIRECT_POINTER_SIZE (VARHDRSZ_EXTERNAL + sizeof(varatt_indirect))
 
 /*
+ *	The information at the start of the compressed toast data.
+ */
+typedef struct toast_compress_header
+{
+	int32		vl_len_;		/* varlena header (do not touch directly!) */
+	int32		rawsize;
+} toast_compress_header;
+
+/*
+ * Utilities for manipulation of header information for compressed
+ * toast entries.
+ */
+#define TOAST_COMPRESS_HDRSZ		((int32) sizeof(toast_compress_header))
+#define TOAST_COMPRESS_RAWSIZE(ptr) (((toast_compress_header *) (ptr))->rawsize)
+#define TOAST_COMPRESS_RAWDATA(ptr) \
+	(((char *) (ptr)) + TOAST_COMPRESS_HDRSZ)
+#define TOAST_COMPRESS_SET_RAWSIZE(ptr, len) \
+	(((toast_compress_header *) (ptr))->rawsize = (len))
+
+/*
  * Testing whether an externally-stored value is compressed now requires
  * comparing extsize (the actual length of the external data) to rawsize
  * (the original uncompressed datum's size).  The latter includes VARHDRSZ
@@ -202,6 +223,24 @@ extern Datum toast_flatten_tuple_to_datum(HeapTupleHeader tup,
 extern Datum toast_compress_datum(Datum value);
 
 /* ----------
+ * toast_fetch_datum -
+ *
+ *	Reconstruct an in memory Datum from the chunks saved
+ *	in the toast relation
+ * ----------
+ */
+extern struct varlena *toast_fetch_datum(struct varlena *attr);
+
+/* ----------
+ * toast_decompress_datum_partial -
+ *
+ * Decompress a datum partially by saving its state
+ * ----------
+ */
+extern int toast_decompress_datum_partial(struct varlena *source,
+	struct varlena *dest, PGLZ_DecompressState *state, int32 until);
+
+/* ----------
  * toast_raw_datum_size -
  *
  *	Return the raw (detoasted) size of a varlena datum
diff --git a/src/include/common/pg_lzcompress.h b/src/include/common/pg_lzcompress.h
index dbd51d5..3378d57 100644
--- a/src/include/common/pg_lzcompress.h
+++ b/src/include/common/pg_lzcompress.h
@@ -65,6 +65,16 @@ typedef struct PGLZ_Strategy
 } PGLZ_Strategy;
 
 
+typedef struct PGLZ_DecompressState
+{
+	int32		until;	/* decompress until this value */
+
+	/* internal values */
+	int32		sp;
+	int32		dp;
+} PGLZ_DecompressState;
+
+
 /* ----------
  * The standard strategies
  *
@@ -86,6 +96,6 @@ extern const PGLZ_Strategy *const PGLZ_strategy_always;
 extern int32 pglz_compress(const char *source, int32 slen, char *dest,
 			  const PGLZ_Strategy *strategy);
 extern int32 pglz_decompress(const char *source, int32 slen, char *dest,
-				int32 rawsize);
+				int32 rawsize, PGLZ_DecompressState *state);
 
 #endif   /* _PG_LZCOMPRESS_H_ */