WIP

Author: Nikita Glukhov

src/backend/access/common/detoast.c

@@ -343,6 +343,8 @@ create_detoast_iterator(struct varlena *attr)
 			/* initialize state for pglz_decompress_iterate() */
 			iter->ctrl = 0;
 			iter->ctrlc = INVALID_CTRLC;
+			iter->len = 0;
+			iter->off = 0;
 		}
 		else
 		{
@@ -368,7 +370,7 @@ create_detoast_iterator(struct varlena *attr)
 		return create_detoast_iterator(attr);
 
 	}
-	else if (VARATT_IS_COMPRESSED(attr))
+	else if (1 && VARATT_IS_COMPRESSED(attr))
 	{
 		ToastBuffer *buf;
 

src/backend/access/common/toast_internals.c

@@ -906,9 +906,33 @@ pglz_decompress_iterate(ToastBuffer *source, ToastBuffer *dest,
 		(source->limit == source->capacity ? source->limit : (source->limit - 4));
 	sp = (const unsigned char *) source->position;
 	dp = (unsigned char *) dest->limit;
-	if (destend < (unsigned char *) dest->capacity)
+	if (destend > (unsigned char *) dest->capacity)
 		destend = (unsigned char *) dest->capacity;
 
+	if (iter->len)
+	{
+		int32		len = iter->len;
+		int32		off = iter->off;
+		int32		copylen = Min(len, destend - dp);
+		int32		remlen = len - copylen;
+
+		while (copylen--)
+		{
+			*dp = dp[-off];
+			dp++;
+		}
+
+		iter->len = remlen;
+
+		if (dp >= destend)
+		{
+			dest->limit = (char *) dp;
+			return;
+		}
+
+		Assert(remlen == 0);
+	}
+
 	while (sp < srcend && dp < destend)
 	{
 		/*
@@ -929,7 +953,6 @@ pglz_decompress_iterate(ToastBuffer *source, ToastBuffer *dest,
 			ctrlc = 0;
 		}
 
-
 		for (; ctrlc < INVALID_CTRLC && sp < srcend && dp < destend; ctrlc++)
 		{
 
@@ -946,6 +969,7 @@ pglz_decompress_iterate(ToastBuffer *source, ToastBuffer *dest,
 				 */
 				int32		len;
 				int32		off;
+				int32		copylen;
 
 				len = (sp[0] & 0x0f) + 3;
 				off = ((sp[0] & 0xf0) << 4) | sp[1];
@@ -959,17 +983,21 @@ pglz_decompress_iterate(ToastBuffer *source, ToastBuffer *dest,
 				 * areas could overlap; to prevent possible uncertainty, we
 				 * copy only non-overlapping regions.
 				 */
-				len = Min(len, destend - dp);
-				while (off < len)
+				copylen = Min(len, destend - dp);
+				iter->len = len - copylen;
+
+				while (off < copylen)
 				{
 					/* see comments in common/pg_lzcompress.c */
 					memcpy(dp, dp - off, off);
-					len -= off;
+					copylen -= off;
 					dp += off;
 					off += off;
 				}
-				memcpy(dp, dp - off, len);
-				dp += len;
+				memcpy(dp, dp - off, copylen);
+				dp += copylen;
+
+				iter->off = off;
 			}
 			else
 			{

src/include/access/detoast.h

@@ -133,6 +133,8 @@ typedef struct DetoastIteratorData
 	unsigned char		ctrl;
 	int					ctrlc;
 	int					nrefs;
+	int32				len;
+	int32				off;
 	bool				compressed;		/* toast value is compressed? */
 	bool				done;
 }			DetoastIteratorData;
@@ -184,16 +186,16 @@ detoast_iterate(DetoastIterator detoast_iter, const char *destend)
 	if (!detoast_iter->compressed)
 		destend = NULL;
 
-	if (destend)
+	if (1 && destend)
 	{
 		const char *srcend = (const char *)
 			(fetch_iter->buf->limit == fetch_iter->buf->capacity ?
 			fetch_iter->buf->limit : fetch_iter->buf->limit - 4);
 
-		if (fetch_iter->buf->position >= srcend)
+		if (fetch_iter->buf->position >= srcend && !fetch_iter->done)
 			fetch_datum_iterate(fetch_iter);
 	}
-	else
+	else if (!fetch_iter->done)
 		fetch_datum_iterate(fetch_iter);
 
 	if (detoast_iter->compressed)