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postgis_foreach.go
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postgis_foreach.go
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package postgis
import (
"context"
"fmt"
"log"
"os"
"strings"
"github.com/terranodo/tegola"
"github.com/terranodo/tegola/wkb"
)
func (p *Provider) Layer(name string) (Layer, bool) {
if name == "" {
return p.layers[p.firstlayer], true
}
plyr, ok := p.layers[name]
return plyr, ok
}
func (p *Provider) ForEachFeature(ctx context.Context, layerName string, tile tegola.Tile, fn func(layer Layer, gid uint64, geom wkb.Geometry, tags map[string]interface{}) error) error {
plyr, ok := p.Layer(layerName)
if !ok {
return fmt.Errorf("layer (%v) not found ", layerName)
}
sql, err := replaceTokens(&plyr, tile)
if err != nil {
return fmt.Errorf("error running layer (%v) SQL (%v): %v", layerName, sql, err)
}
if strings.Contains(os.Getenv("SQL_DEBUG"), "EXECUTE_SQL") {
log.Printf("SQL_DEBUG:EXECUTE_SQL for layer (%v): %v", layerName, sql)
}
// do a quick context check:
if err := ctx.Err(); err != nil {
return err
}
rows, err := p.pool.Query(sql)
if err != nil {
return fmt.Errorf("error running layer (%v) SQL (%v): %v", layerName, sql, err)
}
defer rows.Close()
// fetch rows FieldDescriptions. this gives us the OID for the data types returned to aid in decoding
fdescs := rows.FieldDescriptions()
for rows.Next() {
// do a quick context check:
if err := ctx.Err(); err != nil {
return err
}
// fetch row values
vals, err := rows.Values()
if err != nil {
return fmt.Errorf("error running layer (%v) SQL (%v): %v", layerName, sql, err)
}
gid, geobytes, tags, err := decipherFields(ctx, plyr.GeomFieldName(), plyr.IDFieldName(), fdescs, vals)
if err != nil {
switch err {
case context.Canceled:
return err
default:
return fmt.Errorf("For layer (%v) %v", plyr.Name(), err)
}
}
// decode our WKB
geom, err := wkb.DecodeBytes(geobytes)
if err != nil {
return fmt.Errorf("unable to decode layer (%v) geometry field (%v) into wkb where (%v = %v). err: %v", layerName, plyr.GeomFieldName(), plyr.IDFieldName(), gid, err)
}
if err = fn(plyr, gid, geom, tags); err != nil {
return err
}
}
return nil
}