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50 lines
1.6 KiB
50 lines
1.6 KiB
'use strict';
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function TablesExtentBackend (pgQueryRunner) {
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this.pgQueryRunner = pgQueryRunner;
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}
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module.exports = TablesExtentBackend;
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/**
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* Given a username and a list of tables it will return the estimated extent in SRID 4326 for all the tables based on
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* the_geom_webmercator (SRID 3857) column.
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*
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* @param {String} username
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* @param {Array} tableNames The named can be schema qualified, so this accepts both `schema_name.table_name` and
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* `table_name` format as valid input
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* @param {Function} callback function(err, result) {Object} result with `west`, `south`, `east`, `north`
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*/
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TablesExtentBackend.prototype.getBounds = function (username, tables, callback) {
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var estimatedExtentSQLs = tables.map(function (table) {
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return "ST_EstimatedExtent('" + table.schema_name + "', '" + table.table_name + "', 'the_geom_webmercator')";
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});
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var query = [
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'WITH ext as (' +
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'SELECT ST_Transform(ST_SetSRID(ST_Extent(ST_Union(ARRAY[',
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estimatedExtentSQLs.join(','),
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'])), 3857), 4326) geom)',
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'SELECT',
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'ST_XMin(geom) west,',
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'ST_YMin(geom) south,',
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'ST_XMax(geom) east,',
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'ST_YMax(geom) north',
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'FROM ext'
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].join(' ');
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this.pgQueryRunner.run(username, query, function handleBoundsResult (err, rows) {
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if (err) {
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var msg = err.message ? err.message : err;
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return callback(new Error('could not fetch source tables: ' + msg));
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}
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var result = null;
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if (rows.length > 0) {
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result = {
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bbox: rows[0]
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};
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}
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callback(null, result);
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});
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};
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