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Only do approximate attribute deduplication when writing tiles

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Erica Fischer
2024-02-01 16:06:42 -08:00
parent 910aff8fe7
commit c42b34b498
2 changed files with 16 additions and 32 deletions
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mvt.cpp
+15 -30
View File
@@ -15,6 +15,7 @@
#include "milo/dtoa_milo.h" #include "milo/dtoa_milo.h"
#include "errors.hpp" #include "errors.hpp"
#include "serial.hpp" #include "serial.hpp"
#include "text.hpp"
mvt_geometry::mvt_geometry(int nop, long long nx, long long ny) { mvt_geometry::mvt_geometry(int nop, long long nx, long long ny) {
this->op = nop; this->op = nop;
@@ -592,41 +593,25 @@ std::string mvt_value::toString() const {
} }
void mvt_layer::tag(mvt_feature &feature, std::string const &key, mvt_value const &value) { void mvt_layer::tag(mvt_feature &feature, std::string const &key, mvt_value const &value) {
size_t ko, vo; size_t key_hash = std::hash<std::string>()(key) % dedup.size();
if (dedup[key_hash] >= 0 &&
// initialize lazily the first time anyone tags an attribute dedup[key_hash] < (ssize_t) keys.size() &&
// to save the time of doing it in decode, which never actually matters. keys[dedup[key_hash]] == key) {
// only tile writers actually need this. } else {
if (key_map.size() == 0) { dedup[key_hash] = keys.size();
for (size_t i = 0; i < keys.size(); i++) {
key_map.emplace(keys[i], i);
}
for (size_t i = 0; i < values.size(); i++) {
value_map.emplace(values[i], i);
}
}
std::unordered_map<std::string, size_t>::iterator ki = key_map.find(key);
std::unordered_map<mvt_value, size_t>::iterator vi = value_map.find(value);
if (ki == key_map.end()) {
ko = keys.size();
keys.push_back(key); keys.push_back(key);
key_map.emplace(key, ko);
} else {
ko = ki->second;
} }
feature.tags.push_back(dedup[key_hash]);
if (vi == value_map.end()) { size_t value_hash = std::hash<mvt_value>()(value) % dedup.size();
vo = values.size(); if (dedup[value_hash] >= 0 &&
dedup[value_hash] < (ssize_t) values.size() &&
values[dedup[value_hash]] == value) {
} else {
dedup[value_hash] = values.size();
values.push_back(value); values.push_back(value);
value_map.emplace(value, vo);
} else {
vo = vi->second;
} }
feature.tags.push_back(dedup[value_hash]);
feature.tags.push_back(ko);
feature.tags.push_back(vo);
} }
bool is_integer(const char *s, long long *v) { bool is_integer(const char *s, long long *v) {
mvt.hpp
+1 -2
View File
@@ -174,8 +174,7 @@ struct mvt_layer {
void tag(mvt_feature &feature, std::string const &key, mvt_value const &value); void tag(mvt_feature &feature, std::string const &key, mvt_value const &value);
// For tracking the key-value constants already used in this layer // For tracking the key-value constants already used in this layer
std::unordered_map<std::string, size_t> key_map{}; std::vector<ssize_t> dedup = std::vector<ssize_t>(65536, -1);
std::unordered_map<mvt_value, size_t> value_map{};
}; };
struct mvt_tile { struct mvt_tile {