Add documentation SQL API copyfrom/copyto end points,

and make small modifications arising from that task

app/controllers/copy_controller.js

@@ -114,7 +114,11 @@ CopyController.prototype.handleCopyTo = function (req, res, next) {
             pgstream.on('error', next);
             pgstream.on('end', cb);
             if (_.isString(filename)) {
-                var contentDisposition = "attachment; filename*=UTF-8''" + encodeURIComponent(filename);
+                var contentDisposition = "attachment; filename=" + encodeURIComponent(filename);
+                res.setHeader("Content-Disposition", contentDisposition);
+            } else {
+                filename = 'carto-sql-copyto.dmp';
+                var contentDisposition = "attachment; filename=" + encodeURIComponent(filename);
                 res.setHeader("Content-Disposition", contentDisposition);
             }
             res.setHeader("Content-Type", "application/octet-stream");

doc/API.md

@@ -17,6 +17,7 @@ Remember that in order to access, read or modify data in private tables, you wil
 * [Making calls to the SQL API](making_calls.md)
 * [Creating Tables with the SQL API](creating_tables.md)
 * [Batch Queries](batch_queries.md)
+* [Copy Queries](copy_queries.md)
 * [Handling Geospatial Data](handling_geospatial_data.md)
 * [Query Optimizations](query_optimizations.md)
 * [API Version Vumber](version.md)

doc/copy_queries.md

@@ -0,0 +1,153 @@
+# Copy Queries
+
+Copy queries allow you to use the [PostgreSQL copy command](https://www.postgresql.org/docs/10/static/sql-copy.html) for efficient streaming of data to and from CARTO.
+
+The support for copy is split across two API end points:
+
+* `http://{username}.carto.com/api/v2/copyfrom` for uploading data to CARTO
+* `http://{username}.carto.com/api/v2/copyto` for exporting data out of CARTO
+
+## Copy From
+
+The PostgreSQL `COPY` command is extremely fast, but requires very precise inputs:
+
+* A `COPY` command that describes the table and columns of the upload file, and the format of the file.
+* An upload file that exactly matches the `COPY` command.
+
+If the `COPY` command and the target table do not match, the upload will fail.
+
+In addition, for a table to be readable by CARTO, it must have a minimum of three columns with specific data types:
+
+* `cartodb_id`, a `serial` primary key 
+* `the_geom`, a geometry in the ESPG:4326 (aka long/lat) projection
+* `the_geom_webmercator`, a geometry in the ESPG:3857 (aka web mercator) projection
+
+Creating a new CARTO table with all the right triggers and columns can is tricky, so here is an example:
+
+    -- create the table using the *required* columns and a 
+    -- couple more
+    CREATE TABLE upload_example (
+        the_geom geometry,
+        name text,
+        age integer
+    );
+
+    -- adds the 'cartodb_id' and 'the_geom_webmercator'
+    -- adds the required triggers and indexes
+    SELECT CDB_CartodbfyTable('upload_example');
+    
+Now you are read to upload your file. Suppose you have a CSV file like this:
+
+    the_geom,name,age
+    SRID=4326;POINT(-126 54),North West,89
+    SRID=4326;POINT(-96 34),South East,99
+    SRID=4326;POINT(-6 -25),Souther Easter,124
+
+The `COPY` command to upload this file needs to specify the file format (CSV), the fact that there is a header line before the actual data begins, and enumerate the columns that are in the file so they can be matched to the table columns.
+
+    COPY upload_example (the_geom, name, age) 
+    FROM STDIN WITH (FORMAT csv, HEADER true)
+
+The `FROM STDIN` option tells the database that the input will come from a data stream, and the SQL API will read our uploaded file and use it to feed the stream.
+
+To actually run upload, you will need a tool or script that can generate a `multipart/form-data` POST, so here are a few examples in different languages.
+
+### CURL Example
+
+The [curl](https://curl.haxx.se/) utility makes it easy to run web requests from the commandline, and supports multi-part file upload, so it can feed the `copyfrom` end point.
+
+Assuming that you have already created the table, and that the CSV file is named "upload_example.csv":
+
+    curl \
+      --form sql="COPY upload_example (the_geom, name, age) FROM STDIN WITH (FORMAT csv, HEADER true)" \
+      --form file=@upload_example.csv \
+      http://{username}.carto.com/api/v2/copyfrom?api_key={api_key}
+
+**Important:** When supplying the "sql" parameter as a form field, it must come **before** the "file" parameter, or the upload will fail. Alternatively, you can supply the "sql" parameter on the URL line.
+
+### Python Example
+
+The [Requests](http://docs.python-requests.org/en/master/user/quickstart/) library for HTTP makes doing a file upload relatively terse. 
+
+    import requests
+
+    api_key = {api_key}
+    username = {api_key}
+    upload_file = 'upload_example.csv'
+    sql = "COPY upload_example (the_geom, name, age) FROM STDIN WITH (FORMAT csv, HEADER true)"
+
+    url = "http://%s.carto.com/api/v2/copyfrom" % username    
+    with open(upload_file, 'rb') as f:
+        r = requests.post(url, params={'api_key':api_key, 'sql':sql}, files={'file': f})
+        if r.status_code != 200:
+            print r.text
+        else:
+            status = r.json()
+            print "Success: %s rows imported" % status['total_rows']
+
+A slightly more sophisticated script could read the headers from the CSV and compose the `COPY` command on the fly.
+
+### Response Format
+
+A successful upload will return with status code 200, and a small JSON with information about the upload.
+
+    {"time":0.046,"total_rows":10}
+
+A failed upload will return with status code 400 and a larger JSON with the PostgreSQL error string, and a stack trace from the SQL API.
+
+    {"error":["Unexpected field"],
+     "stack":"Error: Unexpected field
+        at makeError (/repos/CartoDB-SQL-API/node_modules/multer/lib/make-error.js:12:13)
+        at wrappedFileFilter (/repos/CartoDB-SQL-API/node_modules/multer/index.js:39:19)
+        ...
+        at emitMany (events.js:127:13)
+        at SBMH.emit (events.js:201:7)"}
+    
+## Copy To
+
+Using the `copyto` end point to extract data bypasses the usual JSON formatting applied by the SQL API, so it can dump more data, faster. However, it has the restriction that it will only output in a handful of formats:
+
+* PgSQL [text format](https://www.postgresql.org/docs/10/static/sql-copy.html#id-1.9.3.52.9.2),
+* [CSV](https://www.postgresql.org/docs/10/static/sql-copy.html#id-1.9.3.52.9.3), and
+* PgSQL [binary format](https://www.postgresql.org/docs/10/static/sql-copy.html#id-1.9.3.52.9.4).
+
+"Copy to" is a simple HTTP GET end point, so any tool or language can be easily used to download data, supplying the following parameters in the URL:
+
+* `sql`, the "COPY" command to extract the data.
+* `filename`, the filename to put in the "Content-disposition" HTTP header. Useful for tools that automatically save the download to a file name.
+* `api_key`, your API key for reading non-public tables.
+
+
+### CURL Example
+
+    curl \
+        --output upload_example_dl.csv \
+        "http://{username}.carto.com/api/v2/copyfrom?sql=COPY+upload_example+TO+stdout+WITH(FORMAT+csv,HEADER+true)&api_key={api_key}"
+
+### Python Example
+
+    import requests
+    import re
+
+    api_key = {api_key}
+    username = {api_key}
+    download_file = 'upload_example_dl.csv'
+    sql = "COPY upload_example (the_geom, name, age) TO stdout WITH (FORMAT csv, HEADER true)"
+
+    # request the download, specifying desired file name
+    url = "http://%s.carto.com/api/v2/copyto" % username    
+    r = requests.get(url, params={'api_key':api_key, 'sql':sql, 'filename':download_file})
+    r.raise_for_status()
+
+    # read save file name from response headers
+    d = r.headers['content-disposition']
+    savefilename = re.findall("filename=(.+)", d)
+
+    if len(savefilename) > 0:
+        with open(savefilename[0], 'wb') as handle:
+            for block in r.iter_content(1024):
+                handle.write(block)        
+        print "Downloaded to: %s" % savefilename
+    else:
+        print "Error: could not find read file name from headers"
+