geom format in postGIS use to print in google maps android - postgresql

Question

a greeting, a friend happened to me a route of transportation and I step in the following format:
0102000020E610000049020000F2D077B7B23A53C0F03504C7651428C07E703E75AC3A53C07E37DDB2431428C07E8AE3C...
He told me it was a MultiLineString. I used the PostGIS function:
SELECT St_asewkt ('0102000020E6100000810200 .....');
with this i supposedly should be able to get the wkt format that I can
get the coordinates and use it on google maps api to paint a path in android, but when using it throws me empty. Help me please
I need to get something like MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4)) ... to get lat lng coordinates to paint it in google maps api with android.
To summarize what I have is this value
0102000020E6100000810200 ..... and would like to paint it in android with google maps api, that's why I try to get the coordinates that function.

Answer 1

What you have is Well know binary, WKB, which is explained on this page along with its companion well known text (WKT), but in an ASCII (hex) representation, see the docs
If you do something like:
select st_setsrid(st_makepoint(50, -2),4326);
you will see 0101000020E6100000000000000000494000000000000000C0, similar to what you have.
You can insert these directly into a db with
create table test (g geometry);
insert into test(g) values(ST_GeomFromEWKB(E'\\x0101000020E6100000000000000000494000000000000000C0')
where the E'\\x indicates that you are inserted a hex string, see binary format docs.
If you now do
select g from test;
you will get your WKB back and if you do
select st_astext(g) from test;
you will see the more human-readable WKT format.
The best way to load data in the correct format is to use:
COPY table_name FROM your_file.csv CSV;
where your wkb would be, as is, unquoted, in the your_file.csv.