Tables Example¶

The tables client exposes a highly scalable backend for ingesting data and performing various types of queries, such as geospatial and temporal, over that data. This example creates a new table, ingests some rows, performs some basic queries, deletes some rows, shares the table with others, and then deletes the table.

The API reference for these methods and classes is at descarteslabs.tables.

import os
from tempfile import mkstemp

from descarteslabs.tables import Tables

t = Tables()


First let’s download a sample dataset in the form of a shape file so that we don’t have to create our own. We will use active fire data from NASA FIRMS (https://firms.modaps.eosdis.nasa.gov/usfs/active_fire) and assume that it was saved to a file called /tmp/modis_fire.zip. Example command to download: wget -O /tmp/modis_fire.zip https://firms.modaps.eosdis.nasa.gov/data/active_fire/modis-c6.1/shapes/zips/MODIS_C6_1_USA_contiguous_and_Hawaii_7d.zip

import requests

url = "https://cdn.descarteslabs.com/docs/MODIS_C6_1_USA_contiguous_and_Hawaii_7d.zip"
r = requests.get(url)

fd, tmpf = mkstemp(suffix=".zip")
try:
with os.fdopen(fd, mode="w+b") as f:
f.write(r.content)

################################################
# Once you have data, the next step is to create a table that supports the features in
# this shape file.  We need a schema and an SRID, and a quick way to get that is by
# using :meth:Tables.inspect_dataset <descarteslabs.tables.inspect_dataset> Note
# that this method of deriving the schema and srid should not be relied upon without
# manually inspecting the output due to the sheer amount of conversions possible. For
# example, converting a date type may not translate properly so it is encumbent on
# the user to ensure everything looks correct before creating a table.
schema, srid = t.inspect_dataset(tmpf)
print(schema, srid)

################################################
# Now let's create our table with :meth:Tables.create_table
# <descarteslabs.tables.create_table>. The table must have a primary key, which is
# either provided on creation or created by the service. We'll create one on our own
# and make it auto-increment.
from uuid import uuid4

table_name = f"fires_{uuid4().hex}"
schema["properties"]["ID"] = "auto"
t.create_table(table_name, srid=srid, schema=schema, primary_key="ID")

################################################
# Now that we've created the table, we can start inserting rows into it. We have the
# dataset from earlier, so let's just insert that using :meth:Tables.insert_rows
# <descarteslabs.tables.insert_rows>.  Like many other asynchronous client calls in
# the platform, a job ID is returned that can be used to poll the status of the job.
# :meth:Tables.wait_until_completion <descarteslabs.tables.wait_until_completion>
# can be used to halt execution of the program until the ingest job succeeds.
jobid = t.upload_file(tmpf, table_name)
t.wait_until_completion(jobid)

finally:
try:
os.remove(tmpf)
except Exception:
pass


Out:

{'properties': {'LATITUDE': 'float', 'LONGITUDE': 'float', 'BRIGHTNESS': 'float', 'SCAN': 'float', 'TRACK': 'float', 'ACQ_DATE': 'date', 'ACQ_TIME': 'str', 'SATELLITE': 'str', 'CONFIDENCE': 'int', 'VERSION': 'str', 'BRIGHT_T31': 'float', 'FRP': 'float', 'DAYNIGHT': 'str'}, 'geometry': 'Point'} 4326


Once the data has been ingested, the ibis library provides an interface for us to lazily evalute queries and retrieve them as Geo/DataFrames.

fires = t.table(table_name)
print(fires.execute())


Out:

      BRIGHT_T31 VERSION  SCAN  ...    ID BRIGHTNESS                         geom
0         284.23  6.1NRT  1.76  ...     1     302.88   POINT (-71.42392 18.14990)
1         286.31  6.1NRT  1.76  ...     2     307.28   POINT (-71.41471 18.14881)
2         290.08  6.1NRT  1.43  ...     3     312.93   POINT (-70.34927 18.92936)
3         289.21  6.1NRT  1.44  ...     4     307.17   POINT (-70.36263 18.92716)
4         267.33  6.1NRT  1.22  ...     5     300.35   POINT (-98.32987 34.66922)
...          ...     ...   ...  ...   ...        ...                          ...
2526      288.01  6.1NRT  4.57  ...  2527     310.09   POINT (-93.11199 17.84056)
2527      288.30  6.1NRT  4.57  ...  2528     304.44   POINT (-93.11552 17.85654)
2528      284.12  6.1NRT  1.26  ...  2529     303.03  POINT (-101.44954 26.88698)
2529      273.84  6.1NRT  1.40  ...  2530     302.29  POINT (-121.65136 38.13739)
2530      272.59  6.1NRT  1.40  ...  2531     302.66  POINT (-121.63574 38.13445)

[2531 rows x 15 columns]


There are many different types of queries that can be performed. For example, to select specific columns:

print(fires["ID", "LONGITUDE", "LATITUDE", "ACQ_TIME"].execute())


Out:

        ID  LONGITUDE  LATITUDE ACQ_TIME
0        1  -71.42392  18.14990     0236
1        2  -71.41471  18.14881     0236
2        3  -70.34927  18.92936     0236
3        4  -70.36263  18.92716     0236
4        5  -98.32987  34.66922     0418
...    ...        ...       ...      ...
2526  2527  -93.11199  17.84056     0718
2527  2528  -93.11552  17.85654     0718
2528  2529 -101.44954  26.88698     0852
2529  2530 -121.65136  38.13739     1028
2530  2531 -121.63574  38.13445     1028

[2531 rows x 4 columns]


A more in depth example: let’s find the first row with SATELLITE == ‘T’ whose geometry intersects with the highest confidence field. Note that you will need the ibis library to do this intersection, which is installed as a dependency of the tables client

import ibis

confidence = fires["CONFIDENCE", "geom"].execute()
confidence = confidence[confidence["CONFIDENCE"] > 90]
df_geom = fires[
(fires.SATELLITE == "T")
& fires.geom.intersects(ibis.literal(confidence.iloc[0].geom, type="point;4326"))
]
print(df_geom.execute())


Out:

   BRIGHT_T31 VERSION  SCAN  ...  ID BRIGHTNESS                        geom
0      291.59  6.1NRT  1.08  ...   7     332.13  POINT (-92.49234 17.89659)

[1 rows x 15 columns]


If we want to remove some rows from the table, we need to get a list of the primary keys associated with those rows. We can use the Tables.delete_rows method to achieve this. Let’s delete every row with < 20 confidence.

to_delete = fires[fires.CONFIDENCE < 20].ID.execute()
jobid = t.delete_rows(to_delete.to_list(), table_name)
t.wait_until_completion(jobid)


Sharing is handled by the Discover service. Therefore, we will need the Discover client to do this.

from descarteslabs.discover import Discover, Organization

d = Discover()


To share a table you own with someone as a “viewer” (i.e. read-only), use Discover.discover.table.share

d.table(table_name).share(with_=Organization("descarteslabs"), as_="viewer")


To change access to a table from viewer to editor (i.e. read/write), use Discover.discover.table.replace_shares

d.table(table_name).replace_shares(
user=Organization("descarteslabs"), from_role="viewer", to_role="editor"
)


Finally, to revoke access to a table use Discover.discover.table.revoke

d.table(table_name).revoke(from_=Organization("descarteslabs"), as_="editor")


Once you are finished with a table, you can delete the entire thing with Tables.delete_table

t.delete_table(table_name)


Total running time of the script: ( 0 minutes 18.089 seconds)

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