python - Why is Spark's show() function very slow? -


i have

df.select("*").filter(df.itemid==itemid).show()

and never terminated, if do

print df.select("*").filter(df.itemid==itemid)

it prints in less second. why this?

that's because select , filter building execution instructions, aren't doing data. then, when call show executes instructions. if isn't terminating, i'd review logs see if there errors or connection issues. or maybe dataset still large - try taking 5 see if comes quick.


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