# Performance regression in version 0.2.18

**URL:** <https://discuss.hail.is/t/performance-regression-in-version-0-2-18/1026>\
**Category:** Updates\
**Created:** [August 1, 2019, 7:11pm UTC](https://discuss.hail.is/t/performance-regression-in-version-0-2-18/1026 "2019-08-01T19:11:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![tpoterba](https://yyz2.discourse-cdn.com/flex036/user_avatar/discuss.hail.is/tpoterba/32/61_2.png) [@tpoterba](https://discuss.hail.is/u/tpoterba)\
**Post date:** [August 1, 2019, 7:11pm UTC](https://discuss.hail.is/t/performance-regression-in-version-0-2-18/1026/1 "2019-08-01T19:11:42Z")

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We are in the unfortunate situation of finding and fixing a severe performance regression in back-to-back releases of Hail. In 0.2.19, we fixed a problem that only existed in 0.2.18 and led to extremely slow Table/MatrixTable read steps (large hang time before read started) **for tables written in 0.2.18**.

Please update to 0.2.19, released today, and see the [change log](https://hail.is/docs/0.2/change_log.html) for full patch notes.

_ **Edit for clarification** _: files generated in 0.2.18 are perfectly usable in 0.2.19 or later. The problem was the reader code in 0.2.18, not the files themselves.

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**Author:** ![tpoterba](https://yyz2.discourse-cdn.com/flex036/user_avatar/discuss.hail.is/tpoterba/32/61_2.png) [@tpoterba](https://discuss.hail.is/u/tpoterba)\
**Post date:** [August 1, 2019, 7:11pm UTC](https://discuss.hail.is/t/performance-regression-in-version-0-2-18/1026/2 "2019-08-01T19:11:56Z")

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