query-id-with-xor.patch

diff --git a/src/backend/utils/misc/queryjumble.c b/src/backend/utils/misc/queryjumble.c
index f004a9ce8c..225940d40c 100644
--- a/src/backend/utils/misc/queryjumble.c
+++ b/src/backend/utils/misc/queryjumble.c
@@ -106,9 +106,10 @@ JumbleQuery(Query *query, const char *querytext)
 	{
 		jstate = (JumbleState *) palloc(sizeof(JumbleState));
 
-		/* Set up workspace for query jumbling */
-		jstate->jumble = (unsigned char *) palloc(JUMBLE_SIZE);
-		jstate->jumble_len = 0;
+		/* Initialize state for query jumbling */
+		jstate->j.id = 0;
+		jstate->nextbyte = 0;
+		/* Initialize state for tracking where constants are */
 		jstate->clocations_buf_size = 32;
 		jstate->clocations = (LocationLen *)
 			palloc(jstate->clocations_buf_size * sizeof(LocationLen));
@@ -117,9 +118,7 @@ JumbleQuery(Query *query, const char *querytext)
 
 		/* Compute query ID and mark the Query node with it */
 		JumbleQueryInternal(jstate, query);
-		query->queryId = DatumGetUInt64(hash_any_extended(jstate->jumble,
-														  jstate->jumble_len,
-														  0));
+		query->queryId = jstate->j.id;
 
 		/*
 		 * If we are unlucky enough to get a hash of zero, use 1 instead, to
@@ -167,34 +166,17 @@ compute_utility_query_id(const char *query_text, int query_location, int query_l
 static void
 AppendJumble(JumbleState *jstate, const unsigned char *item, Size size)
 {
-	unsigned char *jumble = jstate->jumble;
-	Size		jumble_len = jstate->jumble_len;
+	int			nextbyte = jstate->nextbyte;
 
-	/*
-	 * Whenever the jumble buffer is full, we hash the current contents and
-	 * reset the buffer to contain just that hash value, thus relying on the
-	 * hash to summarize everything so far.
-	 */
 	while (size > 0)
 	{
-		Size		part_size;
-
-		if (jumble_len >= JUMBLE_SIZE)
-		{
-			uint64		start_hash;
-
-			start_hash = DatumGetUInt64(hash_any_extended(jumble,
-														  JUMBLE_SIZE, 0));
-			memcpy(jumble, &start_hash, sizeof(start_hash));
-			jumble_len = sizeof(start_hash);
-		}
-		part_size = Min(size, JUMBLE_SIZE - jumble_len);
-		memcpy(jumble + jumble_len, item, part_size);
-		jumble_len += part_size;
-		item += part_size;
-		size -= part_size;
+		jstate->j.bytes[nextbyte] ^= *item++;
+		nextbyte++;
+		if (nextbyte >= sizeof(uint64))
+			nextbyte = 0;
+		size--;
 	}
-	jstate->jumble_len = jumble_len;
+	jstate->nextbyte = nextbyte;
 }
 
 /*
diff --git a/src/include/utils/queryjumble.h b/src/include/utils/queryjumble.h
index 83ba7339fa..d01712af4d 100644
--- a/src/include/utils/queryjumble.h
+++ b/src/include/utils/queryjumble.h
@@ -16,8 +16,6 @@
 
 #include "nodes/parsenodes.h"
 
-#define JUMBLE_SIZE				1024	/* query serialization buffer size */
-
 /*
  * Struct for tracking locations/lengths of constants during normalization
  */
@@ -33,11 +31,13 @@ typedef struct LocationLen
  */
 typedef struct JumbleState
 {
-	/* Jumble of current query tree */
-	unsigned char *jumble;
-
-	/* Number of bytes used in jumble[] */
-	Size		jumble_len;
+	/* Working state for accumulating a 64-bit query ID */
+	union
+	{
+		unsigned char bytes[sizeof(uint64)];
+		uint64		id;
+	}			j;
+	int			nextbyte;		/* index of next byte to update in j.bytes[] */
 
 	/* Array of locations of constants that should be removed */
 	LocationLen *clocations;