45 lines
1.7 KiB
Markdown
45 lines
1.7 KiB
Markdown
# Compress Synapse State Tables
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An experimental tool that reads in the rows from `state_groups_state` and
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`state_group_edges` tables for a particular room and calculates the changes that
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could be made that (hopefully) will significantly reduce the number of rows.
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This tool currently *does not* write to the database in any way, so should be
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safe to run. If the `-o` option is specified then SQL will be written to the
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given file that would change the tables to match the calculated state. (Note
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that if `-t` is given then each change to a particular state group is wrapped
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in a transaction)
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## Algorithm
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The algorithm works by attempting to create a tree of deltas, produced by
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appending state groups to different "levels". Each level has a maximum size, where
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each state group is appended to the lowest level that is not full.
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This produces a graph that looks approximately like the following, in the case
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of having two levels with the bottom level (L1) having a maximum size of 3:
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```
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L2 <-------------------- L2 <---------- ...
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^--- L1 <--- L1 <--- L1 ^--- L1 <--- L1 <--- L1
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```
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The sizes and number of levels used can be controlled via `-l`.
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## Example
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```
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$ synapse-compress-state -p "postgresql://localhost/synapse" -r '!some_room:example.com'
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Fetching state from DB for room '!some_room:example.com'...
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Got initial state from database. Checking for any missing state groups...
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Number of state groups: 73904
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Number of rows in current table: 2240043
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Number of rows after compression: 165754 (7.40%)
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Compression Statistics:
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Number of forced resets due to lacking prev: 34
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Number of compressed rows caused by the above: 17092
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Number of state groups changed: 2748
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New state map matches old one
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```
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