使用psycopg2 python库构建SQL动态查询并使用良好的转换类型工具

Question

我有一些问题要设计一个好的算法,它使用这里描述的psycopg2库的规范

我想构建一个等于此字符串的动态查询:

SELECT ST_GeomFromText('POLYGON((0.0 0.0,20.0 0.0,20.0 20.0,0.0 20.0,0.0 0.0))');

如您所见,我的POLYGON对象包含多个点,在一个简单的csv文件中读取some.csv,其中包含:

0.0;0.0
20.0;0.0
20.0;20.0
0.0;20.0
0.0;0.0

所以我动态构建查询,csv中行/数据的功能.

这里我的程序生成要执行的SQL查询字符串:

import psycopg2
import csv 

# list of points
lXy = []

DSN= "dbname='testS' user='postgres' password='postgres' host='localhost'"
conn = psycopg2.connect(DSN)

curs = conn.cursor()

def genPointText(curs,x,y):
    generatedPoint = "%s %s" % (x,y)
    return generatedPoint

#Lecture fichier csv
polygonFile = open('some.csv', 'rb')
readerCSV = csv.reader(polygonFile,delimiter = ';')

for coordinates in readerCSV:
    lXy.append(genPointText(curs,float(coordinates[0]),float(coordinates[1])))

# function of list concatenation by separator
def convert(myList,separator):
    return separator.join([str(i) for i in myList])

# construct simple query with psycopg
def genPolygonText(curs,l):
    # http://initd.org/psycopg/docs/usage.html#python-types-adaptation
    generatedPolygon = "POLYGON((%s))" % convert(l, ",")
    return generatedPolygon

def executeWKT(curs,geomObject,srid):
    try:
            # geometry ST_GeomFromText(text WKT, integer srid);
        finalWKT = "SELECT ST_GeomFromText('%s');" % (geomObject) 
        print finalWKT
        curs.execute(finalWKT)
    except psycopg2.ProgrammingError,err:
        print "ERROR = " , err

polygonQuery = genPolygonText(curs,lXy)
executeWKT(curs,polygonQuery,4326)

正如你所看到的,这是有效的,但由于python对象和sql postgresql对象之间的转换问题,这种方式不正确.

在文档中,我只看到了为静态查询提供和转换数据的示例.您是否知道在查询的动态构建中使用正确类型创建正确字符串的"优雅"方法？

更新1:

正如你所看到的,当我在这个简单的例子中使用psycopg类型转换函数时,我有这样的错误:

query = "ST_GeomFromText('POLYGON(( 52.146542 19.050557, 52.148430 19.045527, 52.149525 19.045831, 52.147400 19.050780, 52.147400 19.050780, 52.146542 19.050557))',4326)"
name = "my_table"

try:
    curs.execute('INSERT INTO %s(name, url, id, point_geom, poly_geom) VALUES (%s);', (name,query))
except psycopg2.ProgrammingError,err:
    print "ERROR = " , err

错误等于:

ERROR =  ERREUR:  erreur de syntaxe sur ou près de « E'my_table' »
LINE 1: INSERT INTO E'my_table'(name, poly_geom) VALUES (E'ST_GeomFr...

更新2:

最后的代码,感谢stackoverflow用户!

#info lib : http://www.initd.org/psycopg/docs/
import psycopg2
# info lib : http://docs.python.org/2/library/csv.html
import csv 

# list of points
lXy = []

DSN= "dbname='testS' user='postgres' password='postgres' host='localhost'"

print "Opening connection using dns:", DSN
conn = psycopg2.connect(DSN)

curs = conn.cursor()

def genPointText(curs,x,y):
    generatedPoint = "%s %s" % (x,y)
    return generatedPoint

#Lecture fichier csv
polygonFile = open('some.csv', 'rb')
readerCSV = csv.reader(polygonFile,delimiter = ';')

for coordinates in readerCSV:
    lXy.append(genPointText(curs,float(coordinates[0]),float(coordinates[1])))

# function of list concatenation by separator
def convert(myList,separator):
    return separator.join([str(i) for i in myList])

# construct simple query with psycopg
def genPolygonText(l):
    # http://initd.org/psycopg/docs/usage.html#python-types-adaptation
    generatedPolygon = "POLYGON((%s))" % convert(l, ",")
    return generatedPolygon

def generateInsert(curs,tableName,name,geomObject):
    curs.execute('INSERT INTO binome1(name,geom) VALUES (%s, %s);' , (name,geomObject))


def create_db_binome(conn,name):

    curs = conn.cursor()

    SQL = (
        "CREATE TABLE %s"
        " ("
        " polyname character varying(15),"
        " geom geometry,"
        " id serial NOT NULL,"
        " CONSTRAINT id_key PRIMARY KEY (id)"
        " )" 
        " WITH ("
        " OIDS=FALSE"
        " );"
        " ALTER TABLE %s OWNER TO postgres;"
        ) %(name,name)
    try:
      #print SQL
      curs.execute(SQL)

    except psycopg2.ProgrammingError,err:
      conn.rollback()
      dropQuery = "ALTER TABLE %s DROP CONSTRAINT id_key; DROP TABLE %s;" % (name,name)
      curs.execute(dropQuery)
      curs.execute(SQL)

    conn.commit()

def insert_geometry(polyname,tablename,geometry):

    escaped_name = tablename.replace('""','""')

    try:
        test = 'INSERT INTO %s(polyname, geom) VALUES(%%s, ST_GeomFromText(%%s,%%s))' % (escaped_name)
        curs.execute(test, (tablename, geometry, 4326))
        conn.commit()
    except psycopg2.ProgrammingError,err:
        print "ERROR = " , err

################
# PROGRAM MAIN #
################

polygonQuery = genPolygonText(lXy)
srid = 4326
table = "binome1"

create_db_binome(conn,table)
insert_geometry("Berlin",table,polygonQuery)
insert_geometry("Paris",table,polygonQuery)

polygonFile.close()
conn.close()

Answer 1

您正在尝试将表名作为参数传递.如果您只是查看PostgreSQL错误日志,您可能会立即看到这一点.

您试图通过psycopg2作为参数传递的表名正在被转义,产生如下查询:

INSERT INTO E'my_table'(name, url, id, point_geom, poly_geom) VALUES (E'ST_GeomFromText(''POLYGON(( 52.146542 19.050557, 52.148430 19.045527, 52.149525 19.045831, 52.147400 19.050780, 52.147400 19.050780, 52.146542 19.050557))'',4326)');'

这不是你想要的,也不会起作用; 你不能像文字一样逃避表名.您必须使用普通的Python字符串插值来构造动态SQL,您只能将参数化语句占位符用于实际的文字值.

params = ('POLYGON(( 52.146542 19.050557, 52.148430 19.045527, 52.149525 19.045831, 52.147400 19.050780, 52.147400 19.050780, 52.146542 19.050557))',4326)
escaped_name = name.replace('"",'""')
curs.execute('INSERT INTO "%s"(name, url, id, point_geom, poly_geom) VALUES (ST_GeomFromText(%%s,%%s));' % escaped_name, params)

看看我如何直接插入名称以生成查询字符串:

INSERT INTO my_table(name, url, id, point_geom, poly_geom) VALUES (ST_GeomFromText(%s,%s));

(通过%替换%%转换为普通%).然后我将该查询与定义的字符串POLYGON和另一个参数ST_GeomFromText作为查询参数一起使用.

我没有测试过这个,但它应该给你正确的想法并帮助解释什么是错的.

在进行这样的字符串插值时非常小心,这是SQL注入的一个简单途径.我在上面显示的代码中做了非常粗略的引用,但是如果你的客户端库提供了一个,我想要使用正确的标识符引用功能.