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Merge pull request #51 from mapbox/zxystream-statement

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Prepared statement rather than batch/offset for zxystream
This commit is contained in:
Young Hahn
2015-01-16 17:08:11 -05:00
parent f912cc5d05 62831d95bb
commit 89f2791711
2 changed files with 32 additions and 21 deletions
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50
lib/zxystream.js
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@@ -6,22 +6,13 @@ util.inherits(ZXYStream, stream.Readable);
// Readable stream of line-delimited z/x/y coordinates
// contained within the MBTiles `tiles` table/view.
//
// The `batch` option exists to allow tests to check that
// multiple calls to `_read` are handled properly. IRL the
// default offset of 1000 should be reasonably efficient
// and not worth messing with.
function ZXYStream(source, options) {
if (!source) throw new TypeError('MBTiles source required');
options = options || {};
if (options.batch !== undefined && typeof options.batch !== 'number')
throw new TypeError('options.batch must be a positive integer');
this.source = source;
this.batch = options.batch || 1000;
this.offset = 0;
stream.Readable.call(this);
}
@@ -38,15 +29,38 @@ ZXYStream.prototype._read = function() {
});
}
this.source._db.all('SELECT zoom_level AS z, tile_column AS x, tile_row AS y FROM ' + this.table + ' LIMIT ' + this.batch + ' OFFSET ' + this.offset, function(err, rows) {
if (err && err.code === 'SQLITE_ERROR' && /no such table/.test(err.message)) return stream.push(null);
if (err) return stream.emit('error', err);
if (!rows.length) return stream.push(null);
stream.offset += stream.batch;
var chunk = '';
for (var i = 0; i < rows.length; i++) chunk += toLine(rows[i]);
stream.push(chunk);
});
// Prepare sql statement
if (!stream.statement) {
stream.statement = this.source._db.prepare('SELECT zoom_level AS z, tile_column AS x, tile_row AS y FROM ' + this.table, function(err) {
if (err && err.code === 'SQLITE_ERROR' && /no such table/.test(err.message)) return stream.push(null);
return stream._read();
});
return;
}
var lines = '';
var error;
var remaining = stream.batch;
for (var i = 0; i < stream.batch; i++) stream.statement.get(afterGet);
function afterGet(err, row) {
if (err && err.code === 'SQLITE_ERROR' && /no such table/.test(err.message)) {
// no-op
} else if (err) {
error = err;
} else if (!row) {
// no-op
} else {
lines += toLine(row);
}
if (!--remaining) {
if (error) {
stream.emit('error', error);
} else {
stream.push(lines || null);
}
}
}
};
function toLine(row) {

3
test/zxystream.js
View File

@@ -17,7 +17,6 @@ tape('zxystream default batch', function(assert) {
assert.deepEqual(stream.source, source, 'sets stream.source');
assert.deepEqual(stream.batch, 1000, 'sets stream.batch = 1000');
assert.deepEqual(stream.offset, 0, 'sets stream.offset = 0');
stream.on('data', function(lines) {
assert.equal(stream.table, 'map');
@@ -50,7 +49,6 @@ tape('zxystream batch = 10', function(assert) {
assert.deepEqual(stream.source, source, 'sets stream.source');
assert.deepEqual(stream.batch, 10, 'sets stream.batch = 10');
assert.deepEqual(stream.offset, 0, 'sets stream.offset = 0');
stream.on('data', function(lines) {
assert.equal(stream.table, 'map');
@@ -90,7 +88,6 @@ tape('zxystream unindexed zxystream', function(assert) {
assert.deepEqual(stream.source, source, 'sets stream.source');
assert.deepEqual(stream.batch, 1000, 'sets stream.batch = 1000');
assert.deepEqual(stream.offset, 0, 'sets stream.offset = 0');
stream.on('data', function(lines) {
assert.equal(stream.table, 'tiles');