1 files changed, 102 insertions, 2 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index be7bc46038f..4eeeeaf0a60 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -19,6 +19,7 @@
 #include "funcapi.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
+#include "port/simd.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/date.h"
@@ -1595,6 +1596,18 @@ escape_json(StringInfo buf, const char *str)
 }
 
 /*
+ * Define the number of bytes that escape_json_with_len will look ahead in the
+ * input string before flushing the input string to the destination buffer.
+ * Looking ahead too far could result in cachelines being evicted that will
+ * need to be reloaded in order to perform the appendBinaryStringInfo call.
+ * Smaller values will result in a larger number of calls to
+ * appendBinaryStringInfo and introduce additional function call overhead.
+ * Values larger than the size of L1d cache will likely result in worse
+ * performance.
+ */
+#define ESCAPE_JSON_FLUSH_AFTER 512
+
+/*
  * escape_json_with_len
  *		Produce a JSON string literal, properly escaping the possibly not
  *		NUL-terminated characters in 'str'.  'len' defines the number of bytes
@@ -1603,11 +1616,98 @@ escape_json(StringInfo buf, const char *str)
 void
 escape_json_with_len(StringInfo buf, const char *str, int len)
 {
+	int			vlen;
+
+	Assert(len >= 0);
+
+	/*
+	 * Since we know the minimum length we'll need to append, let's just
+	 * enlarge the buffer now rather than incrementally making more space when
+	 * we run out.  Add two extra bytes for the enclosing quotes.
+	 */
+	enlargeStringInfo(buf, len + 2);
+
+	/*
+	 * Figure out how many bytes to process using SIMD.  Round 'len' down to
+	 * the previous multiple of sizeof(Vector8), assuming that's a power-of-2.
+	 */
+	vlen = len & (int) (~(sizeof(Vector8) - 1));
+
 	appendStringInfoCharMacro(buf, '"');
 
-	for (int i = 0; i < len; i++)
-		escape_json_char(buf, str[i]);
+	for (int i = 0, copypos = 0;;)
+	{
+		/*
+		 * To speed this up, try searching sizeof(Vector8) bytes at once for
+		 * special characters that we need to escape.  When we find one, we
+		 * fall out of the Vector8 loop and copy the portion we've vector
+		 * searched and then we process sizeof(Vector8) bytes one byte at a
+		 * time.  Once done, come back and try doing vector searching again.
+		 * We'll also process any remaining bytes at the tail end of the
+		 * string byte-by-byte.  This optimization assumes that most chunks of
+		 * sizeof(Vector8) bytes won't contain any special characters.
+		 */
+		for (; i < vlen; i += sizeof(Vector8))
+		{
+			Vector8		chunk;
+
+			vector8_load(&chunk, (const uint8 *) &str[i]);
+
+			/*
+			 * Break on anything less than ' ' or if we find a '"' or '\\'.
+			 * Those need special handling.  That's done in the per-byte loop.
+			 */
+			if (vector8_has_le(chunk, (unsigned char) 0x1F) ||
+				vector8_has(chunk, (unsigned char) '"') ||
+				vector8_has(chunk, (unsigned char) '\\'))
+				break;
+
+#ifdef ESCAPE_JSON_FLUSH_AFTER
+
+			/*
+			 * Flush what's been checked so far out to the destination buffer
+			 * every so often to avoid having to re-read cachelines when
+			 * escaping large strings.
+			 */
+			if (i - copypos >= ESCAPE_JSON_FLUSH_AFTER)
+			{
+				appendBinaryStringInfo(buf, &str[copypos], i - copypos);
+				copypos = i;
+			}
+#endif
+		}
+
+		/*
+		 * Write to the destination up to the point that we've vector searched
+		 * so far.  Do this only when switching into per-byte mode rather than
+		 * once every sizeof(Vector8) bytes.
+		 */
+		if (copypos < i)
+		{
+			appendBinaryStringInfo(buf, &str[copypos], i - copypos);
+			copypos = i;
+		}
+
+		/*
+		 * Per-byte loop for Vector8s containing special chars and for
+		 * processing the tail of the string.
+		 */
+		for (int b = 0; b < sizeof(Vector8); b++)
+		{
+			/* check if we've finished */
+			if (i == len)
+				goto done;
+
+			Assert(i < len);
+
+			escape_json_char(buf, str[i++]);
+		}
+
+		copypos = i;
+		/* We're not done yet.  Try the vector search again. */
+	}
 
+done:
 	appendStringInfoCharMacro(buf, '"');
 }