attempt to fix the unknown column-stats error

clonedb.py

@@ -19,6 +19,7 @@ Options:
 """
 import logging
 import re
+import subprocess
 from subprocess import Popen, PIPE, CalledProcessError
 import sys
 
@@ -73,6 +74,17 @@ def _print(msg, end=False):
     print(f'\r{msg}', end='' if not end else '\n', flush=True)
 
 
+def fetch_mysqldump_version():
+    p = subprocess.run('mysqldump --version', shell=True, capture_output=True)
+    out, err = p.stdout.decode('utf-8'), p.stderr.decode('utf-8')
+    if err:
+        raise RuntimeError('mysqldump can not be found, is it installed on this machine?')
+    fork = "mariadb" if "MariaDB" in out else "mysql"
+    match = re.search(r"Ver ((?:\d+\.?)+)", out)
+    version = match.group(1) if match else "0"
+    return fork, version
+
+
 class MysqldumpHandler(PipeHandler):
     """ Handle and process the stdout / stderr output from a mysqldump process
     """
@@ -305,6 +317,8 @@ class CloningOperation:
         tables = tables or []
         dump_options = dump_options or []
 
+        mysqldump_version = fetch_mysqldump_version()
+
         base_cmd = ["mysqldump",
                     "--single-transaction",
                     "-u", self.from_server.username,
@@ -316,12 +330,14 @@ class CloningOperation:
                     ]
 
         # <-- fix the occasional 'Unknown table 'COLUMN_STATISTICS' in information_schema' bug
-        try:
-            self.from_server.exec_query("SELECT COLUMN_NAME FROM information_schema.COLUMN_STATISTICS;")
-        except pymysql.err.OperationalError:
-            base_cmd.append("--column-statistics=0")
-        except pymysql.err.MySQLError:
-            pass
+        # https://stackoverflow.com/questions/52423595/mysqldump-couldnt-execute-unknown-table-column-statistics-in-information-sc
+        if mysqldump_version[0] == 'mysql' and mysqldump_version[1] >= "8":
+            try:
+                self.from_server.exec_query("SELECT COLUMN_NAME FROM information_schema.COLUMN_STATISTICS;")
+            except pymysql.err.OperationalError:
+                base_cmd.append("--column-statistics=0")
+            except pymysql.err.MySQLError:
+                pass
         # -->
 
         if self.compress: