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Bodobolero
75baf83fce
## Problem Customers should be able to determine the size of their workload's working set to right size their compute. Since Neon uses Local file cache (LFC) instead of shared buffers on bigger compute nodes to cache pages we need to externalize a means to determine LFC hit ratio in addition to shared buffer hit ratio. Currently the following end user documentation https://github.com/neondatabase/website/blob/fb7cd3af0e90b74bad8c2ef1166e7798bfdefe20/content/docs/manage/endpoints.md?plain=1#L137 is wrong because it describes how to right size a compute node based on shared buffer hit ratio. Note that the existing functionality in extension "neon" is NOT available to end users but only to superuser / cloud_admin. ## Summary of changes - externalize functions and views in neon extension to end users - introduce a new view `NEON_STAT_FILE_CACHE` with the following DDL ```sql CREATE OR REPLACE VIEW NEON_STAT_FILE_CACHE AS WITH lfc_stats AS ( SELECT stat_name, count FROM neon_get_lfc_stats() AS t(stat_name text, count bigint) ), lfc_values AS ( SELECT MAX(CASE WHEN stat_name = 'file_cache_misses' THEN count ELSE NULL END) AS file_cache_misses, MAX(CASE WHEN stat_name = 'file_cache_hits' THEN count ELSE NULL END) AS file_cache_hits, MAX(CASE WHEN stat_name = 'file_cache_used' THEN count ELSE NULL END) AS file_cache_used, MAX(CASE WHEN stat_name = 'file_cache_writes' THEN count ELSE NULL END) AS file_cache_writes, -- Calculate the file_cache_hit_ratio within the same CTE for simplicity CASE WHEN MAX(CASE WHEN stat_name = 'file_cache_misses' THEN count ELSE 0 END) + MAX(CASE WHEN stat_name = 'file_cache_hits' THEN count ELSE 0 END) = 0 THEN NULL ELSE ROUND((MAX(CASE WHEN stat_name = 'file_cache_hits' THEN count ELSE 0 END)::DECIMAL / (MAX(CASE WHEN stat_name = 'file_cache_hits' THEN count ELSE 0 END) + MAX(CASE WHEN stat_name = 'file_cache_misses' THEN count ELSE 0 END))) * 100, 2) END AS file_cache_hit_ratio FROM lfc_stats ) SELECT file_cache_misses, file_cache_hits, file_cache_used, file_cache_writes, file_cache_hit_ratio from lfc_values; ``` This view can be used by an end user as follows: ```sql CREATE EXTENSION NEON; SELECT * from neon. NEON_STAT_FILE_CACHE" ``` The output looks like the following: ``` select * from NEON_STAT_FILE_CACHE; file_cache_misses | file_cache_hits | file_cache_used | file_cache_writes | file_cache_hit_ratio -------------------+-----------------+-----------------+-------------------+---------------------- 2133643 | 108999742 | 607 | 10767410 | 98.08 (1 row) ``` ## Checklist before requesting a review - [x ] I have performed a self-review of my code. - [x ] If it is a core feature, I have added thorough tests. - [ ] Do we need to implement analytics? if so did you add the relevant metrics to the dashboard? - [x ] If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section. ## Checklist before merging - [ ] Do not forget to reformat commit message to not include the above checklist