Develop Reference

SQLAlchemy not execute a query

I'm having a problem with sqlAlchemy when i try to execute a query. My script has been working fine and every query.execute worked good until now. Here is the code:
for i in listaUnificacion:
usu = "'AUTO'"
incabuniper = "'S'"
sCodPersonaPr, sPers = i[0], i[1]
engine = sqla.create_engine(URL_ORACLE)
connection = engine.connect()
seq_query = sqla.Sequence('SEQ_PERUNI')
pnCodSecPerUni = connection.execute(seq_query)
query = "INSERT INTO TABLE1(SEC, CD, CDUNIF, DATE, USU, INCABUNIPER) VALUES({0}, {1}, {2}, SYSDATE, {3}, {4})".format(pnCodSecPerUni, sCodPersonaPr, sPers, str(usu), str(incabuniper))
query = sqla.text(query)
print(query)
connection.execute(query)
query = "UPDATE TABLE2 SET type = 'M' WHERE cd = {}".format(sPers);
connection.execute(query)
query_uni = "DECLARE\
res varchar2(100);\
errorm varchar2(1000);\
BEGIN\
res := USER.FNC({0},{1},{2},'AUTO',errorm);\
END;".format(pnCodSecPerUni, sCodPersonaPr, sPers)
query_uni = sqla.text(query_unifica)
connection.execute(query_uni)
connection.close()
When I try to execute query_unifica, it doesn't work but it doesn't show any error. I put here the execution with some prints:
PARES
(11005202, 11002071)
INSERT INTO TABLE1(SEC, CD, CDUNIF,, DATE, USU, INCABUNIPER)
VALUES(1628226, 11005202, 11002071, SYSDATE, 'AUTO', 'S') --> WORKS FINE
UPDATE TABLE2 SET type = 'M' WHERE cd = 11002071 --> works fine
DECLARE res varchar2(100); errorm
varchar2(1000); BEGIN res :=
USER.FNC(1628226,11005202,11002071,'AUTO',errorm); END; --
> DOSEN'T WORK!!!

Speeding up insertion of point data from netcdf

I've got this netcdf of weather data (one of thousands that require postgresql ingestion). I'm currently capable of inserting each band into a postgis-enabled table at a rate of about 20-23 seconds per band. (for monthly data, there is also daily data that i have yet to test.)
I've heard of different ways of speeding this up using COPY FROM, removing the gid, using ssds, etc... but I'm new to python and have no idea how to store the netcdf data to something I could use COPY FROM or what the best route might be.
If anyone has any other ideas on how to speed this up, please share!
Here is the ingestion script
import netCDF4, psycopg2, time
# Establish connection
db1 = psycopg2.connect("host=localhost dbname=postgis_test user=********** password=********")
cur = db1.cursor()
# Create Table in postgis
print(str(time.ctime()) + " CREATING TABLE")
try:
cur.execute("DROP TABLE IF EXISTS table_name;")
db1.commit()
cur.execute(
"CREATE TABLE table_name (gid serial PRIMARY KEY not null, thedate DATE, thepoint geometry, lon decimal, lat decimal, thevalue decimal);")
db1.commit()
print("TABLE CREATED")
except:
print(psycopg2.DatabaseError)
print("TABLE CREATION FAILED")
rawvalue_nc_file = 'netcdf_file.nc'
nc = netCDF4.Dataset(rawvalue_nc_file, mode='r')
nc.variables.keys()
lat = nc.variables['lat'][:]
lon = nc.variables['lon'][:]
time_var = nc.variables['time']
dtime = netCDF4.num2date(time_var[:], time_var.units)
newtime = [fdate.strftime('%Y-%m-%d') for fdate in dtime]
rawvalue = nc.variables['tx_max'][:]
lathash = {}
lonhash = {}
entry1 = 0
entry2 = 0
lattemp = nc.variables['lat'][:].tolist()
for entry1 in range(lat.size):
lathash[entry1] = lattemp[entry1]
lontemp = nc.variables['lon'][:].tolist()
for entry2 in range(lon.size):
lonhash[entry2] = lontemp[entry2]
for timestep in range(dtime.size):
print(str(time.ctime()) + " " + str(timestep + 1) + "/180")
for _lon in range(lon.size):
for _lat in range(lat.size):
latitude = round(lathash[_lat], 6)
longitude = round(lonhash[_lon], 6)
thedate = newtime[timestep]
thevalue = round(float(rawvalue.data[timestep, _lat, _lon] - 273.15), 3)
if (thevalue > -100):
cur.execute("INSERT INTO table_name (thedate, thepoint, thevalue) VALUES (%s, ST_MakePoint(%s,%s,0), %s)",(thedate, longitude, latitude, thevalue))
db1.commit()
cur.close()
db1.close()
print(" Done!")

If you're certain most of the time is spent in PostgreSQL, and not in any other code of your own, you may want to look at the fast execution helpers, namely cur.execute_values() in your case.
Also, you may want to make sure you're in a transaction, so the database doesn't fall back to an autocommit mode. ("If you do not issue a BEGIN command, then each individual statement has an implicit BEGIN and (if successful) COMMIT wrapped around it.")
Something like this could do the trick -- not tested though.
for timestep in range(dtime.size):
print(str(time.ctime()) + " " + str(timestep + 1) + "/180")
values = []
cur.execute("BEGIN")
for _lon in range(lon.size):
for _lat in range(lat.size):
latitude = round(lathash[_lat], 6)
longitude = round(lonhash[_lon], 6)
thedate = newtime[timestep]
thevalue = round(
float(rawvalue.data[timestep, _lat, _lon] - 273.15), 3
)
if thevalue > -100:
values.append((thedate, longitude, latitude, thevalue))
psycopg2.extras.execute_values(
cur,
"INSERT INTO table_name (thedate, thepoint, thevalue) VALUES %s",
values,
template="(%s, ST_MakePoint(%s,%s,0), %s)"
)
db1.commit()

python MySQLdb query tables iteratively

I'm trying to query one table against the other using Python and MySQLdb. Here's what I've got so far:
db = MySQLdb.connect( host = 'localhost', user = 'user', passwd=
'password', db = 'vacants')
cursor = db.cursor()
numrows = cursor.rowcount
query = "SELECT address, ((20903520) * acos (cos ( radians(38.67054) )* cos(
radians( lat ) ) * cos( radians( `long` ) - radians(-90.22942) ) + sin (
radians(38.67054) ) * sin( radians( lat ) ))) AS distance FROM vacants HAVING
distance < 100;"
cursor.execute(query)
I have one table, cfs, and another, vacants. I want to see for each row in cfs is there a vacant property within 100 feet. So for the ( radians(38.67054) and radians(-90.22942), I need to loop through the cfs table so that each cfs latitude and longitude replaces those two numbers. (That's just a test latitude and longitude we used)
In the end I'd like to have (in a .csv) the vacant property address, the distance from the call for service, and the type of call (which are two separate fields in the calls for service database). Something like this, which is from the query above:
Here's example data - calls for service coordinates:
38.595767638008056,-90.2316138251402
38.57283495467307,-90.24649031378685
38.67497061776659,-90.28415976525395
38.67650431524285,-90.25623757427952
38.591971519414784,-90.27782710145746
38.61272746420862,-90.23292862245287
38.67312983860098,-90.23591869583113
38.625956494342674,-90.18853950906939
38.69044465638584,-90.24339061920696
38.67745024638241,-90.20657832034047
And vacants:
38.67054,-90.22942
38.642956,-90.21466
38.671535,-90.27293
38.666367,-90.23749
38.65339,-90.23141
38.645996,-90.20334
38.60214,-90.224815
38.67265,-90.214134
38.665504,-90.274414
38.668354,-90.269966

This is not the final solution as there is insufficient info (address field? and 20903520 ?) in the question but it might help you get on track by showing how to iterate through both tables and substitute lat, lon from the CFS table into the query applied to the vacants table:
import mysql.connector
cnx1 = mysql.connector.connect(user='root',password='xxxx',host='127.0.0.1',database=db)
cursor1 = cnx1.cursor()
cnx2 = mysql.connector.connect(user='root',password='xxxx',host='127.0.0.1',database=db)
cursor2 = cnx2.cursor()
sql_cfs = ('select lat,lon from cfs')
cursor1.execute(sql_cfs)
for cfs in cursor1:
[cfs_lat,cfs_lon] = cfs
print (cfs_lat,cfs_lon)
query = ("SELECT address, ((20903520) * " \
"acos (cos(radians(lon)) *" \
"cos(radians({})) * " \
"cos(radians({})-radians(lat)) + sin(radians(lon)) * " \
"sin( radians({})))) AS distance " \
"FROM vacants HAVING distance < 100;".format(cfs_lat,cfs_lon,cfs_lat))
print (query)
cursor2.execute(query)
for vacants in cursor2:
print (vacants)

How to use python to ETL between databases?

Using psycopg2, I'm able to select data from a table in one PostgreSQL database connection and INSERT it into a table in a second PostgreSQL database connection.
However, I'm only able to do it by setting the exact feature I want to extract, and writing out separate variables for each column I'm trying to insert.
Does anyone know of a good practice for either:
moving an entire table between databases, or
iterating through features while not having to declare variables for every column you want to move
or...?
Here's the script I'm currently using where you can see the selection of a specific feature, and the creation of variables (it works, but this is not a practical method):
import psycopg2
connDev = psycopg2.connect("host=host1 dbname=dbname1 user=postgres password=*** ")
connQa = psycopg2.connect("host=host2 dbname=dbname2 user=postgres password=*** ")
curDev = connDev.cursor()
curQa = connQa.cursor()
sql = ('INSERT INTO "tempHoods" (nbhd_name, geom) values (%s, %s);')
curDev.execute('select cast(geom as varchar) from "CCD_Neighborhoods" where nbhd_id = 11;')
tempGeom = curDev.fetchone()
curDev.execute('select nbhd_name from "CCD_Neighborhoods" where nbhd_id = 11;')
tempName = curDev.fetchone()
data = (tempName, tempGeom)
curQa.execute (sql, data)
#commit transactions
connDev.commit()
connQa.commit()
#close connections
curDev.close()
curQa.close()
connDev.close()
connQa.close()
One other note is that python allows the ability to explicitly work with SQL functions / data type casting, which for us is important as we work with the GEOMETRY data type. Above you can see I'm casting it to TEXT then dumping it into an existing geometry column in the source table - this will work with MSSQL Server, which is a huge feature in the geospatial community...

In your solution (your solution and your question have a different order of statements) change the lines which start with 'sql = ' and the loop before '#commit transactions' comment to
sql_insert = 'INSERT INTO "tempHoods" (nbhd_id, nbhd_name, typology, notes, geom) values '
sql_values = ['(%s, %s, %s, %s, %s)']
data_values = []
# you can make this larger if you want
# ...try experimenting to see what works best
batch_size = 100
sql_stmt = sql_insert + ','.join(sql_values*batch_size) + ';'
for i, row in enumerate(rows, 1):
data_values += row[:5]
if i % batch_size == 0:
curQa.execute (sql_stmt , data_values )
data_values = []
if (i % batch_size != 0):
sql_stmt = sql_insert + ','.join(sql_values*(i % batch_size)) + ';'
curQa.execute (sql_stmt , data_values )
BTW, I don't think you need to commit. You don't begin any transactions. So there should not be any need to commit them. Certainly, you don't need to commit a cursor if all you did was a bunch of selects on it.

Here's my updated code based on Dmitry's brilliant solution:
import psycopg2
connDev = psycopg2.connect("host=host1 dbname=dpspgisdev user=postgres password=****")
connQa = psycopg2.connect("host=host2 dbname=dpspgisqa user=postgres password=****")
curDev = connDev.cursor()
curQa = connQa.cursor()
print "Truncating Source"
curQa.execute('delete from "tempHoods"')
connQa.commit()
#Get Data
curDev.execute('select nbhd_id, nbhd_name, typology, notes, cast(geom as varchar) from "CCD_Neighborhoods";') #cast geom to varchar and insert into geometry column!
rows = curDev.fetchall()
sql_insert = 'INSERT INTO "tempHoods" (nbhd_id, nbhd_name, typology, notes, geom) values '
sql_values = ['(%s, %s, %s, %s, %s)'] #number of columns selecting / inserting
data_values = []
batch_size = 1000 #customize for size of tables...
sql_stmt = sql_insert + ','.join(sql_values*batch_size) + ';'
for i, row in enumerate(rows, 1):
data_values += row[:5] #relates to number of columns (%s)
if i % batch_size == 0:
curQa.execute (sql_stmt , data_values )
connQa.commit()
print "Inserting..."
data_values = []
if (i % batch_size != 0):
sql_stmt = sql_insert + ','.join(sql_values*(i % batch_size)) + ';'
curQa.execute (sql_stmt, data_values)
print "Last Values..."
connQa.commit()
# close connections
curDev.close()
curQa.close()
connDev.close()
connQa.close()

Python error as using rcost to route in PostgreSQL

I use pyscripter to call PostgreSQL from outside and route my network, and here's my code,
import sys, os
#set up psycopg2 environment
import psycopg2
#driving_distance module
query = """
select *
from driving_distance ($$
select
gid as id,
source::int4 as source,
target::int4 as target,
cost::double precision as cost
from network
$$, %s, %s, %s, %s
)
"""
#make connection between python and postgresql
conn = psycopg2.connect("dbname = 'TC_area' user = 'postgres' host = 'localhost' password = 'xxxx'")
cur = conn.cursor()
#count rows in the table
cur.execute("select count(*) from network")
result = cur.fetchone()
k = result[0] + 1 #number of points = number of segments + 1
#run loops
rs = []
i = 1
while i <= k:
cur.execute(query, (i, 1000000, False, True))
rs.append(cur.fetchall())
i = i + 1
#import csv module
import csv
j = 0
h = 0
ars = []
element = list(rs)
#export data to every row
with open('distMatrix.csv', 'wb') as f:
writer = csv.writer(f, delimiter = ',')
while j <= k - 1:
while h <= k - 1:
rp = element[j][h][1]
ars.append(rp)
h = h + 1
else:
h = 0
writer.writerow(ars)
ars = []
j = j + 1
conn.close()
The result is good, but if I want to use the reverse_cost function in the function driving_distance in PostgreSQL, I just add one line below the 'cost::double precision as cost',
rcost::double precision as reverse_cost
I got this error box popped out after I added this line,
and the error message in python IDLE,
Traceback (most recent call last):
File "C:\Users\Heinz\Documents\pyscript\postgresql\distMatrix.py.py", line 47, in <module>
cur.execute(query, (i, 1000000, False, True))
ProgrammingError: 錯誤: 在"語法錯誤"附近發生 rcost
LINE 7: rcost::double precision as reverse_cost
^
QUERY:
select
gid as id,
source::int4 as source,
target::int4 as target,
cost::double precision as cost
rcost::double precision as reverse_cost
from network
PS. I have altered the table of this network, thus it does have a 'rcost' column, and here's the part of view,
If I execute the code inside pgAdmin, I could successfully get the right result,
SELECT * FROM driving_distance('
SELECT gid as id,
source::int4 AS source,
target::int4 AS target,
cost::double precision as cost,
rcost::double precision as reverse_cost
FROM network',
3, 10000000, false, True);
But I need python to do the loop, how can I solve this problem？
PS. If I set both boolean in the function to FALSE, theoretically the program will ignore rcost and return answers calculated from cost only, but I still got the same error,
The problem seems results from rcost.
I am using PostgreSQL 8.4, python 2.7.6 under Windows 8.1 x64.
UPDATE#1
I changed 2 lines in my script and then it works,
cost::double precision as cost, #need to add a trailing comma if followed by rcost
cur.execute(query, (i, 100000000000, False, True)) #the range must be greater than max of rcost

Your line "cost::double precision as cost" needs a trailing comma.