psycopg2 转义字符

Question

我有一个如下所示的 postgres 查询，并在 psql 上运行查找：

select 
    gcaseid,
    count (*)                          as N,
    array_agg(distinct nvchquestion)   as questions,
    array_agg(nvchanswer)              as answers
from
    case_script,
    case_script_answer
where
    case_script.gscriptid = case_script_answer.gscriptid and
    nvchquestion ilike '%blood pressure%'
group by
    gcaseid
order by
    N desc
;

现在，我想在 Python 中进行类似的查询，这就是我想出的：

import psycopg2

def getAnswers(question):

    query = '''
            select 
                gcaseid,
                count (*)                          as N,
                array_agg(distinct nvchquestion)   as questions,
                array_agg(nvchanswer)              as answers
            from
                case_script,
                case_script_answer
            where
                case_script.gscriptid = case_script_answer.gscriptid and
                nvchquestion ilike %s
            group by
                gcaseid
            order by
                N desc
            ;
    '''%(r"'%%s%'")

    conn = psycopg2.connect("dbname='sos' user='postgres' host='localhost'")
    cur  = conn.cursor()

    cur.mogrify(query, (question,))
    # cur.execute(query, (question,))

    # result = cur.fetchall()

    cur.close()
    conn.close()

    return result

if __name__ == '__main__':

    print getAnswers('blood pressure')
    print 'done'

现在，当我运行这个查询时，我得到了错误：

$ python updateTable.py
Traceback (most recent call last):
  File "updateTable.py", line 39, in <module>
    print getAnswers('blood pressure')
  File "updateTable.py", line 27, in getAnswers
    cur.mogrify(query, (question,))
ValueError: unsupported format character ''' (0x27) at index 442

不确定发生了什么。有没有人可以澄清一下？

Answer 1

在查询中使用 %% 来表示 LIKE 通配符：

execute(" ... ilike %%%s%%", [question])

或者在您的值中用 %s 包围您的值：

execute(" ... ilike %s", ['%' + question + '%']

参见docs about parameters。

Answer 2

最简单的方法是按照的建议将 % 连接到参数：

query = "select 'x' ilike %s"
print (cursor.mogrify(query, ('%x%',)).decode('utf8'))
cursor.execute(query, ('%x%',))
print (cursor.fetchone()[0])

输出：

select 'x' ilike '%x%'
True

但是如果你想保持参数干净使用format:

query = "select 'x' ilike format('%%%%%%1$s%%%%', %s)"
print (cursor.mogrify(query, ('x',)).decode('utf8'))
cursor.execute(query, ('x',))
print (cursor.fetchone()[0])

输出：

select 'x' ilike format('%%%1$s%%', 'x')
True

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