What is mysql wrt buffered cursor python mysql connector

Question

Can someone please give an example to figure this out?

After the query is completed, the MySQLCursorBuffered cursor retrieves the entire result set from the server and buffers the rows. For queries executed using a buffered cursor, row fetch methods such as fetchone () return rows from a set of buffered rows. For unbuffered cursors, rows are not output from the server until the row fetch method is called. In this case, you should definitely get all the rows of the result set before executing any other statements in the same connection or throw an InternalError (Unread result).

thank

Answer 1

I can imagine two ways in which these two types Cursordiffer.

The first way is that if you execute the query using a buffered cursor, you can get the number of rows returned by checking MySQLCursorBuffered.rowcount. However, the rowcountunbuffered cursor attribute returns -1immediately after a method call execute. This basically means that the entire result set has not yet been received from the server. In addition, the attribute of the rowcountunbuffered cursor increases as you retrieve the rows from it, while the attribute of the rowcountbuffered cursor remains the same as you retrieve the rows from it.

The following code snippet attempts to illustrate the above points:

import mysql.connector


conn = mysql.connector.connect(database='db',
                               user='username',
                               password='pass',
                               host='localhost',
                               port=3306)

buffered_cursor = conn.cursor(buffered=True)
unbuffered_cursor = conn.cursor(buffered=False)

create_query = """
drop table if exists people;
create table if not exists people (
    personid int(10) unsigned auto_increment,
    firstname varchar(255),
    lastname varchar(255),
    primary key (personid)
);
insert into people (firstname, lastname)
values ('Jon', 'Bon Jovi'),
('David', 'Bryan'),
('Tico', 'Torres'),
('Phil', 'Xenidis'),
('Hugh', 'McDonald')
"""

# Create and populate a table
results = buffered_cursor.execute(create_query, multi=True)
conn.commit()

buffered_cursor.execute("select * from people")
print("Row count from a buffer cursor:", buffered_cursor.rowcount)
unbuffered_cursor.execute("select * from people")
print("Row count from an unbuffered cursor:", unbuffered_cursor.rowcount)

print()
print("Fetching rows from a buffered cursor: ")

while True:
    try:
        row = next(buffered_cursor)
        print("Row:", row)
        print("Row count:", buffered_cursor.rowcount)
    except StopIteration:
        break

print()
print("Fetching rows from an unbuffered cursor: ")

while True:
    try:
        row = next(unbuffered_cursor)
        print("Row:", row)
        print("Row count:", unbuffered_cursor.rowcount)
    except StopIteration:
        break

- :

Row count from a buffered reader:  5
Row count from an unbuffered reader:  -1

Fetching rows from a buffered cursor:
Row: (1, 'Jon', 'Bon Jovi')
Row count: 5
Row: (2, 'David', 'Bryan')
Row count: 5
Row: (3, 'Tico', 'Torres')
Row count: 5
Row: (4, 'Phil', 'Xenidis')
Row count: 5
Row: (5, 'Hugh', 'McDonald')
Row: 5

Fetching rows from an unbuffered cursor:
Row: (1, 'Jon', 'Bon Jovi')
Row count: 1
Row: (2, 'David', 'Bryan')
Row count: 2
Row: (3, 'Tico', 'Torres')
Row count: 3
Row: (4, 'Phil', 'Xenidis')
Row count: 4
Row: (5, 'Hugh', 'McDonald')
Row count: 5

, rowcount -1 , . .

- , ( ) execute . , , , InternalError, , . :

import mysql.connector


conn = mysql.connector.connect(database='db',
                               user='username',
                               password='pass',
                               host='localhost',
                               port=3306)

buffered_cursor = conn.cursor(buffered=True)
unbuffered_cursor = conn.cursor(buffered=False)

create_query = """
drop table if exists people;
create table if not exists people (
    personid int(10) unsigned auto_increment,
    firstname varchar(255),
    lastname varchar(255),
    primary key (personid)
);
insert into people (firstname, lastname)
values ('Jon', 'Bon Jovi'),
('David', 'Bryan'),
('Tico', 'Torres'),
('Phil', 'Xenidis'),
('Hugh', 'McDonald')
"""

# Create and populate a table
results = buffered_cursor.execute(create_query, multi=True)
conn.commit()

unbuffered_cursor.execute("select * from people")
unbuffered_cursor.fetchone()
buffered_cursor.execute("select * from people")

InternalError , . , , , , . unbuffered_cursor.fetchone() unbuffered_cursor.fetchall(), .

, . , , , .

, .