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Refactor SQL query for DMs History modal

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The ORDER BY timestamp on the DMs Username History endpoint was causing
SQLite to do a full table scan by timestamp instead of indexing on
channel ID. So, instead, we fetch the distinct channel IDs for the
current user and add them to an IN clause on the main query (instead of
a LIKE clause), which causes the index to use the channel_id instead of
timestamp. This may improve CPU performance and speed on this endpoint.
This commit is contained in:
Noah 2025-03-16 11:31:29 -07:00
parent ce47fc18c2
commit 89dd40f77f
1 changed files with 76 additions and 31 deletions
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107
pkg/models/direct_messages.go
View File

@ -5,6 +5,7 @@ import (
"fmt"
"math"
"sort"
"strings"
"time"
"git.kirsle.net/apps/barertc/pkg/config"
@ -261,25 +262,47 @@ func PaginateUsernames(fromUsername, sort string, page, perPage int) ([]string,
orderBy = "timestamp DESC"
}
// Get all our distinct channel IDs to filter the query down: otherwise doing an ORDER BY timestamp
// causes a full table scan index which is very inefficient!
channelIDs, err := GetDistinctChannelIDs(fromUsername)
if err != nil {
return nil, 0, 0, err
}
// No channel IDs = no response to fetch.
if len(channelIDs) == 0 {
return nil, 0, 0, errors.New("you have no direct messages stored on this chat server")
}
var (
cidPlaceholders = "?" + strings.Repeat(",?", len(channelIDs)-1)
params = []interface{}{}
)
for _, cid := range channelIDs {
params = append(params, cid)
}
// Note: for some reason, the SQLite driver doesn't allow a parameterized
// query for ORDER BY (e.g. "ORDER BY ?") - so, since we have already
// whitelisted acceptable orders, use a Sprintf to interpolate that
// directly into the query.
queryStr := fmt.Sprintf(`
SELECT distinct(username)
FROM direct_messages
WHERE channel_id IN (%s)
AND username <> ?
ORDER BY %s
LIMIT ?
OFFSET ?`,
cidPlaceholders,
orderBy,
)
params = append(params, fromUsername, perPage, offset)
// fmt.Println(queryStr)
// fmt.Printf("%v\n", params)
rows, err := DB.Query(
// Note: for some reason, the SQLite driver doesn't allow a parameterized
// query for ORDER BY (e.g. "ORDER BY ?") - so, since we have already
// whitelisted acceptable orders, use a Sprintf to interpolate that
// directly into the query.
fmt.Sprintf(`
SELECT distinct(username)
FROM direct_messages
WHERE (
channel_id LIKE ?
OR channel_id LIKE ?
)
AND username <> ?
ORDER BY %s
LIMIT ?
OFFSET ?`,
orderBy,
),
channelIDs[0], channelIDs[1], fromUsername, perPage, offset,
queryStr,
params...,
)
if err != nil {
return nil, 0, 0, err
@ -296,19 +319,8 @@ func PaginateUsernames(fromUsername, sort string, page, perPage int) ([]string,
result = append(result, username)
}
// Get a total count of usernames.
row := DB.QueryRow(`
SELECT COUNT(distinct(username))
FROM direct_messages
WHERE (
channel_id LIKE ?
OR channel_id LIKE ?
)
AND username <> ?
`, channelIDs[0], channelIDs[1], fromUsername)
if err := row.Scan(&count); err != nil {
return nil, 0, 0, err
}
// The count of distinct channel IDs earlier.
count = len(channelIDs)
pages = int(math.Ceil(float64(count) / float64(perPage)))
if pages < 1 {
@ -318,6 +330,39 @@ func PaginateUsernames(fromUsername, sort string, page, perPage int) ([]string,
return result, count, pages, nil
}
// GetDistinctChannelIDs collects all of the conversation thread IDs the current user is a party to.
func GetDistinctChannelIDs(username string) ([]string, error) {
var (
result = []string{}
channelIDs = []string{
fmt.Sprintf(`@%s:%%`, username),
fmt.Sprintf(`%%:@%s`, username),
}
)
rows, err := DB.Query(`
SELECT distinct(channel_id)
FROM direct_messages
WHERE (
channel_id LIKE ?
OR channel_id LIKE ?
)
`, channelIDs[0], channelIDs[1])
if err != nil {
return nil, err
}
for rows.Next() {
var channelID string
if err := rows.Scan(&channelID); err != nil {
return nil, err
}
result = append(result, channelID)
}
return result, nil
}
// CreateChannelID returns a deterministic channel ID for a direct message conversation.
//
// The usernames (passed in any order) are sorted alphabetically and composed into the channel ID.