db: fix CSV escaping by switching to jackc/pgx

lib/pq has been in maintenance mode for a while, and issue timescale#61 appears
to have run into one of its idiosyncrasies: its COPY implementation
assumes that you're using a query generated via pq.CopyIn(), which uses
the default TEXT format, so it runs all of the incoming data through an
additional escaping layer.

Our code uses CSV by default (and there appears to be no way to use TEXT
format, since we're using the old COPY syntax), which means that
incoming CSV containing its own escapes will be double-escaped and
corrupted. This is most visible with bytea columns, but the tests
currently document additional problems with tab and backslash
characters, and there are probably other problematic cases too.

To fix, switch from lib/pq over to jackc/pgx, and reimplement
db.CopyFromLines() using the PgConn.CopyFrom() API. We were already
depending on a part of this library before, so the new dependency isn't
as big of a change as it would have been otherwise, but the switch isn't
free. The compiled binary gains roughly 1.5 MB in size -- likely due to
jackc's extensive type conversion system, which is unfortunate because
we're not using it. Further optimization could probably be done, at the
expense of having most of the DB logic go through the low-level APIs
rather than database/sql.

We make use of the new sql.Conn.Raw() method to easily drop down to the
lowest API level, so bump our minimum Go version to 1.13. (1.12 has been
EOL for about three years now.) This escaping fix is a breaking change
for anyone who may have already worked around this problem, so bump the
utility's version to 0.4.0.

README.md

@@ -5,7 +5,7 @@ PostgreSQL's built-in `COPY` functionality for bulk inserting data
 into [TimescaleDB.](//github.com/timescale/timescaledb/)
 
 ### Getting started
-You need the Go runtime (1.6+) installed, then simply `go get` this repo:
+You need the Go runtime (1.13+) installed, then simply `go get` this repo:
 ```bash
 $ go install github.com/timescale/timescaledb-parallel-copy/cmd/timescaledb-parallel-copy@latest
 ```

cmd/timescaledb-parallel-copy/main.go

@@ -12,13 +12,14 @@ import (
 	"sync/atomic"
 	"time"
 
-	_ "github.com/lib/pq"
+	_ "github.com/jackc/pgx/v4/stdlib"
+
 	"github.com/timescale/timescaledb-parallel-copy/internal/db"
 )
 
 const (
 	binName    = "timescaledb-parallel-copy"
-	version    = "0.3.0"
+	version    = "0.4.0-dev"
 	tabCharStr = "\\t"
 )
 

go.mod

@@ -1,11 +1,11 @@
 module github.com/timescale/timescaledb-parallel-copy
 
-go 1.12
+go 1.13
 
 require (
-	github.com/jackc/pgconn v1.1.0
+	github.com/jackc/pgconn v1.12.1
+	github.com/jackc/pgx/v4 v4.16.1
 	github.com/jmoiron/sqlx v1.2.0
-	github.com/lib/pq v1.2.0
-	golang.org/x/crypto v0.0.0-20190911031432-227b76d455e7 // indirect
+	github.com/lib/pq v1.10.6 // indirect
 	google.golang.org/appengine v1.6.5 // indirect
 )