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MBTiles: chunk histogram scans by tile_column #93

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Merged
yuiseki merged 2 commits into from
Jan 20, 2026
Merged

MBTiles: chunk histogram scans by tile_column #93

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272f955
Chunk MBTiles histogram scans by tile column
yuiseki Jan 20, 2026
94b20d2
Merge branch 'main' into feat/inspect-histogram-chunking
yuiseki Jan 20, 2026
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143 changes: 124 additions & 19 deletions src/mbtiles.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1227,7 +1227,13 @@ fn build_histogram(
};
let range = (max_len - min_len).max(1);
let bucket_size = ((range as f64) / buckets as f64).ceil() as u64;
let tile_source = tiles_source_clause(&conn)?;
let allow_column_chunk = sample.is_none() && tile_source == "tiles";
let chunk_count = (rayon::current_num_threads() as u64)
.saturating_mul(4)
.max(1);
let query = select_zoom_length_by_zoom_query(&conn)?;
let query_with_column_range = select_zoom_length_by_zoom_and_column_range_query(&conn)?;
let zoom_counts = fetch_zoom_counts(&conn)?;
let zooms = if let Some(target) = zoom {
vec![target]
Expand All @@ -1237,13 +1243,38 @@ fn build_histogram(
let processed = Arc::new(AtomicU64::new(0));
let progress = progress.clone();

let (counts, bytes) = zooms
let mut tasks = Vec::new();
for zoom in &zooms {
if allow_column_chunk && *zoom >= 12 {
if let Some(ranges) = tile_column_chunks(*zoom, chunk_count) {
for range in ranges {
tasks.push((*zoom, Some(range)));
}
} else {
tasks.push((*zoom, None));
}
} else {
tasks.push((*zoom, None));
}
}

let (counts, bytes) = tasks
.into_par_iter()
.map(|zoom| -> Result<(Vec<u64>, Vec<u64>)> {
.map(|(zoom, range)| -> Result<(Vec<u64>, Vec<u64>)> {
let conn = open_readonly_mbtiles(path)?;
apply_read_pragmas(&conn)?;
let mut stmt = conn.prepare(&query).context("prepare histogram scan")?;
let mut rows = stmt.query([zoom]).context("query histogram scan")?;
let mut stmt = if range.is_some() {
conn.prepare(&query_with_column_range)
.context("prepare histogram scan (column range)")?
} else {
conn.prepare(&query).context("prepare histogram scan")?
};
let mut rows = if let Some((col_min, col_max)) = range {
stmt.query(params![zoom, col_min, col_max])
.context("query histogram scan (column range)")?
} else {
stmt.query([zoom]).context("query histogram scan")?
};

let total_tiles_db = *zoom_counts.get(&zoom).unwrap_or(&0);
let mut index: u64 = 0;
Expand Down Expand Up @@ -1384,7 +1415,13 @@ fn build_zoom_histograms(
bar.set_message("building zoom histograms");
bar
};
let tile_source = tiles_source_clause(&conn)?;
let allow_column_chunk = sample.is_none() && tile_source == "tiles";
let chunk_count = (rayon::current_num_threads() as u64)
.saturating_mul(4)
.max(1);
let query = select_zoom_length_by_zoom_query(&conn)?;
let query_with_column_range = select_zoom_length_by_zoom_and_column_range_query(&conn)?;

#[derive(Clone, Copy)]
struct ZoomConfig {
Expand Down Expand Up @@ -1418,18 +1455,41 @@ fn build_zoom_histograms(
}

let zooms = configs.keys().copied().collect::<Vec<_>>();
let mut tasks = Vec::new();
for zoom in &zooms {
if allow_column_chunk && *zoom >= 12 {
if let Some(ranges) = tile_column_chunks(*zoom, chunk_count) {
for range in ranges {
tasks.push((*zoom, Some(range)));
}
} else {
tasks.push((*zoom, None));
}
} else {
tasks.push((*zoom, None));
}
}
let processed = Arc::new(AtomicU64::new(0));
let progress = progress.clone();

let accums = zooms
let accums = tasks
.into_par_iter()
.map(|zoom| -> Result<BTreeMap<u8, ZoomAccum>> {
.map(|(zoom, range)| -> Result<(u8, ZoomAccum)> {
let conn = open_readonly_mbtiles(path)?;
apply_read_pragmas(&conn)?;
let mut stmt = conn
.prepare(&query)
.context("prepare zoom histogram scan")?;
let mut rows = stmt.query([zoom]).context("query zoom histogram scan")?;
let mut stmt = if range.is_some() {
conn.prepare(&query_with_column_range)
.context("prepare zoom histogram scan (column range)")?
} else {
conn.prepare(&query)
.context("prepare zoom histogram scan")?
};
let mut rows = if let Some((col_min, col_max)) = range {
stmt.query(params![zoom, col_min, col_max])
.context("query zoom histogram scan (column range)")?
} else {
stmt.query([zoom]).context("query zoom histogram scan")?
};

let config = configs.get(&zoom).expect("zoom histogram config missing");
let mut accum = ZoomAccum {
Expand Down Expand Up @@ -1481,17 +1541,49 @@ fn build_zoom_histograms(
progress.set_position(total);
}

let mut map = BTreeMap::new();
map.insert(zoom, accum);
Ok(map)
Ok((zoom, accum))
})
.reduce(
|| Ok(BTreeMap::new()),
|left, right| -> Result<BTreeMap<u8, ZoomAccum>> {
let mut left = left?;
let right = right?;
.try_fold(
BTreeMap::new,
|mut map, item| -> Result<BTreeMap<u8, ZoomAccum>> {
let (zoom, accum) = item?;
let entry = map.entry(zoom).or_insert_with(|| ZoomAccum {
min_len: accum.min_len,
max_len: accum.max_len,
bucket_size: accum.bucket_size,
counts: vec![0u64; buckets],
bytes: vec![0u64; buckets],
used_tiles: 0,
used_bytes: 0,
});
for i in 0..buckets {
entry.counts[i] += accum.counts[i];
entry.bytes[i] += accum.bytes[i];
}
entry.used_tiles += accum.used_tiles;
entry.used_bytes += accum.used_bytes;
Ok(map)
},
)
.try_reduce(
BTreeMap::new,
|mut left, right| -> Result<BTreeMap<u8, ZoomAccum>> {
for (zoom, accum) in right {
left.insert(zoom, accum);
let entry = left.entry(zoom).or_insert_with(|| ZoomAccum {
min_len: accum.min_len,
max_len: accum.max_len,
bucket_size: accum.bucket_size,
counts: vec![0u64; buckets],
bytes: vec![0u64; buckets],
used_tiles: 0,
used_bytes: 0,
});
for i in 0..buckets {
entry.counts[i] += accum.counts[i];
entry.bytes[i] += accum.bytes[i];
}
entry.used_tiles += accum.used_tiles;
entry.used_bytes += accum.used_bytes;
}
Ok(left)
},
Expand Down Expand Up @@ -2596,6 +2688,19 @@ fn select_zoom_length_by_zoom_query(conn: &Connection) -> Result<String> {
))
}

fn select_zoom_length_by_zoom_and_column_range_query(conn: &Connection) -> Result<String> {
let source = tiles_source_clause(conn)?;
let data_expr = tiles_data_expr(conn)?;
let (zoom_col, x_col) = if source == "tiles" {
("zoom_level", "tile_column")
} else {
("map.zoom_level", "map.tile_column")
};
Ok(format!(
"SELECT LENGTH({data_expr}) FROM {source} WHERE {zoom_col} = ?1 AND {x_col} BETWEEN ?2 AND ?3",
))
}

fn select_tile_count_query(conn: &Connection, with_zoom: bool) -> Result<String> {
let source = tiles_count_source_clause(conn)?;
let zoom_col = if source == "map" {
Expand Down