MDEV-19522 InnoDB commit fails when FTS_DOC_ID value is greater than 4294967295

InnoDB commit fails when consecutive FTS_DOC_ID value
is greater than 4294967295.
Fix is that InnoDB should remove the delta FTS_DOC_ID
value limitations and fts should encode 8 byte value,
remove FTS_DOC_ID_MAX_STEP variable. Replaced the
fts0vlc.ic file with fts0vlc.h

fts_encode_int(): Should be able to encode 10 bytes value

fts_get_encoded_len(): Should get the length of the value
which has 10 bytes

fts_decode_vlc(): Add debug assertion to verify the maximum
length allowed is 10.

mach_read_uint64_little_endian(): Reads 64 bit stored in
little endian format

Added a unit test case which check for minimum and maximum
value to do the fts encoding

14 files changed, 247 insertions, 231 deletions

diff --git a/storage/innobase/CMakeLists.txt b/storage/innobase/CMakeLists.txt
index b965c4fbb45..ff646e00f39 100644
--- a/storage/innobase/CMakeLists.txt
+++ b/storage/innobase/CMakeLists.txt
@@ -188,3 +188,7 @@ IF(MSVC)
 ENDIF()
 
 ADD_SUBDIRECTORY(${CMAKE_SOURCE_DIR}/extra/mariabackup ${CMAKE_BINARY_DIR}/extra/mariabackup)
+
+IF(WITH_UNIT_TESTS)
+  ADD_SUBDIRECTORY(unittest)
+ENDIF()
diff --git a/storage/innobase/fts/fts0fts.cc b/storage/innobase/fts/fts0fts.cc
index 07077006096..bbe53f4d163 100644
--- a/storage/innobase/fts/fts0fts.cc
+++ b/storage/innobase/fts/fts0fts.cc
@@ -32,7 +32,7 @@ Full Text Search interface
 #include "fts0priv.h"
 #include "fts0types.h"
 #include "fts0types.ic"
-#include "fts0vlc.ic"
+#include "fts0vlc.h"
 #include "fts0plugin.h"
 #include "dict0priv.h"
 #include "dict0stats.h"
@@ -1247,7 +1247,7 @@ fts_cache_node_add_positions(
 	ulint		enc_len;
 	ulint		last_pos;
 	byte*		ptr_start;
-	ulint		doc_id_delta;
+	doc_id_t	doc_id_delta;
 
 #ifdef UNIV_DEBUG
 	if (cache) {
@@ -1258,7 +1258,7 @@ fts_cache_node_add_positions(
 	ut_ad(doc_id >= node->last_doc_id);
 
 	/* Calculate the space required to store the ilist. */
-	doc_id_delta = (ulint)(doc_id - node->last_doc_id);
+	doc_id_delta = doc_id - node->last_doc_id;
 	enc_len = fts_get_encoded_len(doc_id_delta);
 
 	last_pos = 0;
@@ -1307,14 +1307,14 @@ fts_cache_node_add_positions(
 	ptr_start = ptr;
 
 	/* Encode the new fragment. */
-	ptr += fts_encode_int(doc_id_delta, ptr);
+	ptr = fts_encode_int(doc_id_delta, ptr);
 
 	last_pos = 0;
 	for (i = 0; i < ib_vector_size(positions); i++) {
 		ulint	pos = *(static_cast<ulint*>(
 			 ib_vector_get(positions, i)));
 
-		ptr += fts_encode_int(pos - last_pos, ptr);
+		ptr = fts_encode_int(pos - last_pos, ptr);
 		last_pos = pos;
 	}
 
diff --git a/storage/innobase/fts/fts0opt.cc b/storage/innobase/fts/fts0opt.cc
index c4cbbfafff4..2d506a757a0 100644
--- a/storage/innobase/fts/fts0opt.cc
+++ b/storage/innobase/fts/fts0opt.cc
@@ -36,6 +36,7 @@ Completed 2011/7/10 Sunny and Jimmy Yang
 #include "ut0list.h"
 #include "zlib.h"
 #include "fts0opt.h"
+#include "fts0vlc.h"
 
 /** The FTS optimize thread's work queue. */
 ib_wqueue_t* fts_optimize_wq;
@@ -1116,7 +1117,7 @@ fts_optimize_encode_node(
 	ulint		pos_enc_len;
 	doc_id_t	doc_id_delta;
 	dberr_t		error = DB_SUCCESS;
-	byte*		src = enc->src_ilist_ptr;
+	const byte*	src = enc->src_ilist_ptr;
 
 	if (node->first_doc_id == 0) {
 		ut_a(node->last_doc_id == 0);
@@ -1173,7 +1174,7 @@ fts_optimize_encode_node(
 
 	/* Encode the doc id. Cast to ulint, the delta should be small and
 	therefore no loss of precision. */
-	dst += fts_encode_int((ulint) doc_id_delta, dst);
+	dst = fts_encode_int(doc_id_delta, dst);
 
 	/* Copy the encoded pos array. */
 	memcpy(dst, src, pos_enc_len);
@@ -1220,7 +1221,8 @@ fts_optimize_node(
 		doc_id_t	delta;
 		doc_id_t	del_doc_id = FTS_NULL_DOC_ID;
 
-		delta = fts_decode_vlc(&enc->src_ilist_ptr);
+		delta = fts_decode_vlc(
+			(const byte**)&enc->src_ilist_ptr);
 
 test_again:
 		/* Check whether the doc id is in the delete list, if
@@ -1248,7 +1250,7 @@ test_again:
 
 			/* Skip the entries for this document. */
 			while (*enc->src_ilist_ptr) {
-				fts_decode_vlc(&enc->src_ilist_ptr);
+				fts_decode_vlc((const byte**)&enc->src_ilist_ptr);
 			}
 
 			/* Skip the end of word position marker. */
diff --git a/storage/innobase/fts/fts0que.cc b/storage/innobase/fts/fts0que.cc
index b4c72e53afe..965c79bfaa5 100644
--- a/storage/innobase/fts/fts0que.cc
+++ b/storage/innobase/fts/fts0que.cc
@@ -34,6 +34,7 @@ Completed 2011/7/10 Sunny and Jimmy Yang
 #include "fts0pars.h"
 #include "fts0types.h"
 #include "fts0plugin.h"
+#include "fts0vlc.h"
 
 #include <iomanip>
 #include <vector>
@@ -3224,7 +3225,7 @@ fts_query_filter_doc_ids(
 	ulint			len,		/*!< in: doc id ilist size */
 	ibool			calc_doc_count)	/*!< in: whether to remember doc count */
 {
-	byte*		ptr = static_cast<byte*>(data);
+	const byte*	ptr = static_cast<byte*>(data);
 	doc_id_t	doc_id = 0;
 	ulint		decoded = 0;
 	ib_rbt_t*	doc_freqs = word_freq->doc_freqs;
@@ -3234,8 +3235,8 @@ fts_query_filter_doc_ids(
 		ulint		freq = 0;
 		fts_doc_freq_t*	doc_freq;
 		fts_match_t*	match = NULL;
-		ulint		last_pos = 0;
-		ulint		pos = fts_decode_vlc(&ptr);
+		doc_id_t	last_pos = 0;
+		doc_id_t	pos = fts_decode_vlc(&ptr);
 
 		/* Some sanity checks. */
 		if (doc_id == 0) {
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 10e5cbe216f..91d245ad0e2 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -8543,8 +8543,7 @@ calc_row_difference(
 		    && prebuilt->table->fts
 		    && innobase_strcasecmp(
 			field->field_name, FTS_DOC_ID_COL_NAME) == 0) {
-			doc_id = (doc_id_t) mach_read_from_n_little_endian(
-				n_ptr, 8);
+			doc_id = mach_read_uint64_little_endian(n_ptr);
 			if (doc_id == 0) {
 				return(DB_FTS_INVALID_DOCID);
 			}
@@ -8787,16 +8786,6 @@ calc_row_difference(
 					<< innodb_table->name;
 
 				return(DB_FTS_INVALID_DOCID);
-			} else if ((doc_id
-				    - prebuilt->table->fts->cache->next_doc_id)
-				   >= FTS_DOC_ID_MAX_STEP) {
-
-				ib::warn() << "Doc ID " << doc_id << " is too"
-					" big. Its difference with largest"
-					" Doc ID used " << prebuilt->table->fts
-					->cache->next_doc_id - 1
-					<< " cannot exceed or equal to "
-					<< FTS_DOC_ID_MAX_STEP;
 			}
 
 
diff --git a/storage/innobase/handler/i_s.cc b/storage/innobase/handler/i_s.cc
index 03c0efff027..1111d974ad0 100644
--- a/storage/innobase/handler/i_s.cc
+++ b/storage/innobase/handler/i_s.cc
@@ -58,6 +58,7 @@ Modified Dec 29, 2014 Jan Lindström (Added sys_semaphore_waits)
 #include "fil0fil.h"
 #include "fil0crypt.h"
 #include "dict0crea.h"
+#include "fts0vlc.h"
 
 /** The latest successfully looked up innodb_fts_aux_table */
 UNIV_INTERN table_id_t innodb_ft_aux_table_id;
@@ -2775,7 +2776,7 @@ i_s_fts_index_cache_fill_one_index(
 		/* Decrypt the ilist, and display Dod ID and word position */
 		for (ulint i = 0; i < ib_vector_size(word->nodes); i++) {
 			fts_node_t*	node;
-			byte*		ptr;
+			const byte*	ptr;
 			ulint		decoded = 0;
 			doc_id_t	doc_id = 0;
 
@@ -2785,13 +2786,11 @@ i_s_fts_index_cache_fill_one_index(
 			ptr = node->ilist;
 
 			while (decoded < node->ilist_size) {
-				ulint	pos = fts_decode_vlc(&ptr);
 
-				doc_id += pos;
+				doc_id += fts_decode_vlc(&ptr);
 
 				/* Get position info */
 				while (*ptr) {
-					pos = fts_decode_vlc(&ptr);
 
 					OK(field_store_string(
 						   fields[I_S_FTS_WORD],
@@ -2812,7 +2811,7 @@ i_s_fts_index_cache_fill_one_index(
 						   doc_id, true));
 
 					OK(fields[I_S_FTS_ILIST_DOC_POS]->store(
-						   pos, true));
+						   fts_decode_vlc(&ptr), true));
 
 					OK(schema_table_store_record(
 						   thd, table));
@@ -3146,7 +3145,7 @@ i_s_fts_index_table_fill_one_fetch(
 		/* Decrypt the ilist, and display Dod ID and word position */
 		for (ulint i = 0; i < ib_vector_size(word->nodes); i++) {
 			fts_node_t*	node;
-			byte*		ptr;
+			const byte*	ptr;
 			ulint		decoded = 0;
 			doc_id_t	doc_id = 0;
 
@@ -3156,13 +3155,10 @@ i_s_fts_index_table_fill_one_fetch(
 			ptr = node->ilist;
 
 			while (decoded < node->ilist_size) {
-				ulint	pos = fts_decode_vlc(&ptr);
-
-				doc_id += pos;
+				doc_id += fts_decode_vlc(&ptr);
 
 				/* Get position info */
 				while (*ptr) {
-					pos = fts_decode_vlc(&ptr);
 
 					OK(field_store_string(
 						   fields[I_S_FTS_WORD],
@@ -3181,7 +3177,7 @@ i_s_fts_index_table_fill_one_fetch(
 						longlong(doc_id), true));
 
 					OK(fields[I_S_FTS_ILIST_DOC_POS]->store(
-						   pos, true));
+						   fts_decode_vlc(&ptr), true));
 
 					OK(schema_table_store_record(
 						   thd, table));
diff --git a/storage/innobase/include/fts0fts.h b/storage/innobase/include/fts0fts.h
index 84d8ccd26ef..dfac5117c17 100644
--- a/storage/innobase/include/fts0fts.h
+++ b/storage/innobase/include/fts0fts.h
@@ -96,10 +96,6 @@ those defined in mysql file ft_global.h */
 /** Threshold where our optimize thread automatically kicks in */
 #define FTS_OPTIMIZE_THRESHOLD		10000000
 
-/** Threshold to avoid exhausting of doc ids. Consecutive doc id difference
-should not exceed FTS_DOC_ID_MAX_STEP */
-#define FTS_DOC_ID_MAX_STEP		65535
-
 /** Maximum possible Fulltext word length in bytes (assuming mbmaxlen=4) */
 #define FTS_MAX_WORD_LEN		(HA_FT_MAXCHARLEN * 4)
 
diff --git a/storage/innobase/include/fts0types.h b/storage/innobase/include/fts0types.h
index f5760a16c0e..21d32c7d313 100644
--- a/storage/innobase/include/fts0types.h
+++ b/storage/innobase/include/fts0types.h
@@ -315,16 +315,6 @@ int fts_doc_id_cmp(
 	const void*	p2);			/*!< in: id2 */
 
 /******************************************************************//**
-Decode and return the integer that was encoded using our VLC scheme.*/
-UNIV_INLINE
-ulint
-fts_decode_vlc(
-/*===========*/
-			/*!< out: value decoded */
-	byte**	ptr);	/*!< in: ptr to decode from, this ptr is
-			incremented by the number of bytes decoded */
-
-/******************************************************************//**
 Duplicate a string. */
 UNIV_INLINE
 void
@@ -339,28 +329,6 @@ fts_string_dup(
 	mem_heap_t*		heap);		/*!< in: heap to use */
 
 /******************************************************************//**
-Return length of val if it were encoded using our VLC scheme. */
-UNIV_INLINE
-ulint
-fts_get_encoded_len(
-/*================*/
-						/*!< out: length of value
-						 encoded, in bytes */
-	ulint		val);			/*!< in: value to encode */
-
-/******************************************************************//**
-Encode an integer using our VLC scheme and return the length in bytes. */
-UNIV_INLINE
-ulint
-fts_encode_int(
-/*===========*/
-						/*!< out: length of value
-						encoded, in bytes */
-	ulint		val,			/*!< in: value to encode */
-	byte*		buf);			/*!< in: buffer, must have
-						enough space */
-
-/******************************************************************//**
 Get the selected FTS aux INDEX suffix. */
 UNIV_INLINE
 const char*
@@ -381,6 +349,5 @@ fts_select_index(
 	ulint			len);
 
 #include "fts0types.ic"
-#include "fts0vlc.ic"
 
 #endif /* INNOBASE_FTS0TYPES_H */
diff --git a/storage/innobase/include/fts0vlc.h b/storage/innobase/include/fts0vlc.h
new file mode 100644
index 00000000000..d6e6037777e
--- /dev/null
+++ b/storage/innobase/include/fts0vlc.h
@@ -0,0 +1,124 @@
+/**
+
+Copyright (c) 2021, MariaDB Corporation.
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
+**/
+/**
+@file include/fts0vlc.h
+Full text variable length integer encoding/decoding.
+
+Created 2021-10-19 Thirunarayanan Balathandayuthapani
+**/
+
+/** Return length of val if it were encoded using our VLC scheme.
+@param	val	value to encode
+@return length of value encoded, in bytes */
+inline size_t fts_get_encoded_len(doc_id_t val)
+{
+  if (val < static_cast<doc_id_t>(1) << 7)
+    return 1;
+  if (val < static_cast<doc_id_t>(1) << 14)
+    return 2;
+  if (val < static_cast<doc_id_t>(1) << 21)
+    return 3;
+  if (val < static_cast<doc_id_t>(1) << 28)
+    return 4;
+  if (val < static_cast<doc_id_t>(1) << 35)
+    return 5;
+  if (val < static_cast<doc_id_t>(1) << 42)
+    return 6;
+  if (val < static_cast<doc_id_t>(1) << 49)
+    return 7;
+  if (val < static_cast<doc_id_t>(1) << 56)
+    return 8;
+  if (val < static_cast<doc_id_t>(1) << 63)
+    return 9;
+  return 10;
+}
+
+/** Encode an integer using our VLC scheme and return the
+length in bytes.
+@param	val	value to encode
+@param	buf	buffer, must have enough space
+@return length of value encoded, in bytes */
+inline byte *fts_encode_int(doc_id_t val, byte *buf)
+{
+  if (val < static_cast<doc_id_t>(1) << 7)
+    goto add_1;
+  if (val < static_cast<doc_id_t>(1) << 14)
+    goto add_2;
+  if (val < static_cast<doc_id_t>(1) << 21)
+    goto add_3;
+  if (val < static_cast<doc_id_t>(1) << 28)
+    goto add_4;
+  if (val < static_cast<doc_id_t>(1) << 35)
+    goto add_5;
+  if (val < static_cast<doc_id_t>(1) << 42)
+    goto add_6;
+  if (val < static_cast<doc_id_t>(1) << 49)
+    goto add_7;
+  if (val < static_cast<doc_id_t>(1) << 56)
+    goto add_8;
+  if (val < static_cast<doc_id_t>(1) << 63)
+    goto add_9;
+
+  *buf++= static_cast<byte>(val >> 63);
+add_9:
+  *buf++= static_cast<byte>(val >> 56) & 0x7F;
+add_8:
+  *buf++= static_cast<byte>(val >> 49) & 0x7F;
+add_7:
+  *buf++= static_cast<byte>(val >> 42) & 0x7F;
+add_6:
+  *buf++= static_cast<byte>(val >> 35) & 0x7F;
+add_5:
+  *buf++= static_cast<byte>(val >> 28) & 0x7F;
+add_4:
+  *buf++= static_cast<byte>(val >> 21) & 0x7F;
+add_3:
+  *buf++= static_cast<byte>(val >> 14) & 0x7F;
+add_2:
+  *buf++= static_cast<byte>(val >> 7) & 0x7F;
+add_1:
+  *buf++= static_cast<byte>(val) | 0x80;
+  return buf;
+}
+
+/** Decode and return the integer that was encoded using
+our VLC scheme.
+@param	ptr 	pointer to decode from, this ptr is
+		incremented by the number of bytes decoded
+@return value decoded */
+inline doc_id_t fts_decode_vlc(const byte **ptr)
+{
+  ut_d(const byte *const start= *ptr);
+  ut_ad(*start);
+
+  doc_id_t val= 0;
+  for (;;)
+  {
+    byte b= *(*ptr)++;
+    val|= (b & 0x7F);
+
+    /* High-bit on means "last byte in the encoded integer". */
+    if (b & 0x80)
+      break;
+    ut_ad(val < static_cast<doc_id_t>(1) << (64 - 7));
+    val <<= 7;
+  }
+
+  ut_ad(*ptr - start <= 10);
+
+  return(val);
+}
diff --git a/storage/innobase/include/fts0vlc.ic b/storage/innobase/include/fts0vlc.ic
deleted file mode 100644
index 75d8535057e..00000000000
--- a/storage/innobase/include/fts0vlc.ic
+++ /dev/null
@@ -1,142 +0,0 @@
-/*****************************************************************************
-
-Copyright (c) 2007, 2011, Oracle and/or its affiliates. All Rights Reserved.
-
-This program is free software; you can redistribute it and/or modify it under
-the terms of the GNU General Public License as published by the Free Software
-Foundation; version 2 of the License.
-
-This program is distributed in the hope that it will be useful, but WITHOUT
-ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License along with
-this program; if not, write to the Free Software Foundation, Inc.,
-51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
-
-*****************************************************************************/
-
-/******************************************************************//**
-@file include/fts0vlc.ic
-Full text variable length integer encoding/decoding.
-
-Created 2007-03-27 Sunny Bains
-*******************************************************/
-
-#ifndef INNOBASE_FTS0VLC_IC
-#define INNOBASE_FTS0VLC_IC
-
-#include "fts0types.h"
-
-/******************************************************************//**
-Return length of val if it were encoded using our VLC scheme.
-FIXME: We will need to be able encode 8 bytes value
-@return length of value encoded, in bytes */
-UNIV_INLINE
-ulint
-fts_get_encoded_len(
-/*================*/
-	ulint	val)	/* in: value to encode */
-{
-	if (val <= 127) {
-		return(1);
-	} else if (val <= 16383) {
-		return(2);
-	} else if (val <= 2097151) {
-		return(3);
-	} else if (val <= 268435455) {
-		return(4);
-	} else {
-		/* Possibly we should care that on 64-bit machines ulint can
-		contain values that we can't encode in 5 bytes, but
-		fts_encode_int doesn't handle them either so it doesn't much
-		matter. */
-
-		return(5);
-	}
-}
-
-/******************************************************************//**
-Encode an integer using our VLC scheme and return the length in bytes.
-@return length of value encoded, in bytes */
-UNIV_INLINE
-ulint
-fts_encode_int(
-/*===========*/
-	ulint	val,	/* in: value to encode */
-	byte*	buf)	/* in: buffer, must have enough space */
-{
-	ulint	len;
-
-	if (val <= 127) {
-		*buf = (byte) val;
-
-		len = 1;
-	} else if (val <= 16383) {
-		*buf++ = (byte)(val >> 7);
-		*buf = (byte)(val & 0x7F);
-
-		len = 2;
-	} else if (val <= 2097151) {
-		*buf++ = (byte)(val >> 14);
-		*buf++ = (byte)((val >> 7) & 0x7F);
-		*buf = (byte)(val & 0x7F);
-
-		len = 3;
-	} else if (val <= 268435455) {
-		*buf++ = (byte)(val >> 21);
-		*buf++ = (byte)((val >> 14) & 0x7F);
-		*buf++ = (byte)((val >> 7) & 0x7F);
-		*buf = (byte)(val & 0x7F);
-
-		len = 4;
-	} else {
-		/* Best to keep the limitations of the 32/64 bit versions
-		identical, at least for the time being. */
-		ut_ad(val <= 4294967295u);
-
-		*buf++ = (byte)(val >> 28);
-		*buf++ = (byte)((val >> 21) & 0x7F);
-		*buf++ = (byte)((val >> 14) & 0x7F);
-		*buf++ = (byte)((val >> 7) & 0x7F);
-		*buf = (byte)(val & 0x7F);
-
-		len = 5;
-	}
-
-	/* High-bit on means "last byte in the encoded integer". */
-	*buf |= 0x80;
-
-	return(len);
-}
-
-/******************************************************************//**
-Decode and return the integer that was encoded using our VLC scheme.
-@return value decoded */
-UNIV_INLINE
-ulint
-fts_decode_vlc(
-/*===========*/
-	byte**	ptr)	/* in: ptr to decode from, this ptr is
-			incremented by the number of bytes decoded */
-{
-	ulint	val = 0;
-
-	for (;;) {
-		byte	b = **ptr;
-
-		++*ptr;
-		val |= (b & 0x7F);
-
-		/* High-bit on means "last byte in the encoded integer". */
-		if (b & 0x80) {
-			break;
-		} else {
-			val <<= 7;
-		}
-	}
-
-	return(val);
-}
-
-#endif
diff --git a/storage/innobase/include/mach0data.h b/storage/innobase/include/mach0data.h
index 8141c8a91e0..860ef20b8bd 100644
--- a/storage/innobase/include/mach0data.h
+++ b/storage/innobase/include/mach0data.h
@@ -316,6 +316,28 @@ mach_read_from_n_little_endian(
 	const byte*	buf,		/*!< in: from where to read */
 	ulint		buf_size)	/*!< in: from how many bytes to read */
 	MY_ATTRIBUTE((warn_unused_result));
+
+
+/** Reads a 64 bit stored in big endian format
+@param	buf		From where to read
+@return uint64_t */
+UNIV_INLINE
+uint64_t
+mach_read_uint64_little_endian(const byte* buf)
+{
+#ifdef WORDS_BIGENDIAN
+  return
+    uint64_t(buf[0])       | uint64_t(buf[1]) << 8 |
+    uint64_t(buf[2]) << 16 | uint64_t(buf[3]) << 24 |
+    uint64_t(buf[4]) << 32 | uint64_t(buf[5]) << 40 |
+    uint64_t(buf[6]) << 48 | uint64_t(buf[7]) << 56;
+#else
+  uint64_t n;
+  memcpy(&n, buf, sizeof(uint64_t));
+  return n;
+#endif
+}
+
 /*********************************************************//**
 Writes a ulint in the little-endian format. */
 UNIV_INLINE
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index c2f9186d408..6445f67f3c2 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -1465,23 +1465,6 @@ error_exit:
 				trx->error_state = DB_FTS_INVALID_DOCID;
 				goto error_exit;
 			}
-
-			/* Difference between Doc IDs are restricted within
-			4 bytes integer. See fts_get_encoded_len(). Consecutive
-			doc_ids difference should not exceed
-			FTS_DOC_ID_MAX_STEP value. */
-
-			if (doc_id - next_doc_id >= FTS_DOC_ID_MAX_STEP) {
-				 ib::error() << "Doc ID " << doc_id
-					<< " is too big. Its difference with"
-					" largest used Doc ID "
-					<< next_doc_id - 1 << " cannot"
-					" exceed or equal to "
-					<< FTS_DOC_ID_MAX_STEP;
-				err = DB_FTS_INVALID_DOCID;
-				trx->error_state = DB_FTS_INVALID_DOCID;
-				goto error_exit;
-			}
 		}
 
 		if (table->skip_alter_undo) {
diff --git a/storage/innobase/unittest/CMakeLists.txt b/storage/innobase/unittest/CMakeLists.txt
new file mode 100644
index 00000000000..df98cddf73e
--- /dev/null
+++ b/storage/innobase/unittest/CMakeLists.txt
@@ -0,0 +1,22 @@
+# Copyright (c) 2021, MariaDB Corporation.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1335 USA
+
+INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/include
+		    ${CMAKE_SOURCE_DIR}/unittest/mytap
+                    ${CMAKE_SOURCE_DIR}/storage/innobase/include)
+ADD_EXECUTABLE(innodb_fts-t innodb_fts-t.cc)
+TARGET_LINK_LIBRARIES(innodb_fts-t mysys mytap)
+ADD_DEPENDENCIES(innodb_fts-t GenError)
+MY_ADD_TEST(innodb_fts)
diff --git a/storage/innobase/unittest/innodb_fts-t.cc b/storage/innobase/unittest/innodb_fts-t.cc
new file mode 100644
index 00000000000..57585e337c2
--- /dev/null
+++ b/storage/innobase/unittest/innodb_fts-t.cc
@@ -0,0 +1,52 @@
+#include "tap.h"
+#include "fts0fts.h"
+#include "fts0vlc.h"
+
+struct fts_encode_info
+{
+  const byte buf[10];
+  int32_t len;
+  doc_id_t val;
+};
+
+/* Contains fts encoding min & max value for each length bytes */
+static const fts_encode_info fts_info[]=
+{
+  {{0x80}, 1, 0},
+  {{0xFF}, 1, (1 << 7) - 1},
+  {{0x01, 0x80}, 2, 1 << 7},
+  {{0x7F, 0XFF}, 2, (1 << 14) - 1},
+  {{0x01, 0x00, 0x80}, 3, 1 << 14},
+  {{0x7F, 0X7F, 0XFF}, 3, (1 << 21) - 1},
+  {{0x01, 0x00, 0x00, 0x80}, 4, 1 << 21},
+  {{0x7F, 0X7F, 0X7F, 0xFF}, 4, (1 << 28) - 1},
+  {{0x01, 0x00, 0x00, 0x00, 0x80}, 5, 1 << 28},
+  {{0x7F, 0X7F, 0X7F, 0x7F, 0xFF}, 5, (1ULL << 35) - 1},
+  {{0x01, 0x00, 0x00, 0x00, 0x00, 0x80}, 6, 1ULL << 35},
+  {{0x7F, 0X7F, 0X7F, 0x7F, 0x7F, 0xFF}, 6, (1ULL << 42) - 1},
+  {{0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80}, 7, 1ULL << 42},
+  {{0x7F, 0X7F, 0X7F, 0x7F, 0x7F, 0x7F, 0XFF}, 7, (1ULL << 49) - 1},
+  {{0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80}, 8, 1ULL << 49},
+  {{0x7F, 0X7F, 0X7F, 0x7F, 0x7F, 0x7F, 0X7F, 0XFF}, 8, (1ULL << 56) -1},
+  {{0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80}, 9, 1ULL << 56},
+  {{0x7F, 0X7F, 0X7F, 0x7F, 0x7F, 0x7F, 0X7F, 0x7F, 0XFF}, 9, (1ULL << 63) -1},
+  {{0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80}, 10, 1ULL << 63},
+  {{0x01, 0X7F, 0X7F, 0x7F, 0x7F, 0x7F, 0X7F, 0x7F, 0x7F, 0xFF}, 10, ~0ULL}
+};
+
+int main(int, char**)
+{
+  for (int i= array_elements(fts_info); i--;)
+  {
+    byte buf[10];
+    const byte* fts_buf= buf;
+    int32_t len= fts_encode_int(fts_info[i].val, buf) - &buf[0];
+    if (fts_info[i].len == len &&
+        !memcmp(&fts_info[i].buf, buf, len) &&
+        fts_decode_vlc(&fts_buf) == fts_info[i].val &&
+        fts_buf == &buf[len])
+      ok(true, "FTS Encoded for %d bytes", fts_info[i].len);
+    else
+      ok(false, "FTS Encoded for %d bytes", fts_info[i].len);
+  }
+}