panic in group by

[jfontan]

gitbase commit: cffce77ec6b225f3d05390b979138200ee238d1c
go-mysql-server commit: 8796d13

Query:

select commit_author_when, count(commit_files.file_path)
from commits
  natural join commit_files
  natural join ref_commits
where ref_commits.ref_name="master"  limit 1;

Panic:

DEBU[0182] executing query                               query="select commit_author_when, count(commit_files.file_path) from commits natural join commit_files natural join ref_commits where ref_commits.ref_name=\"master\"  limit 1"
INFO[0184] ConnectionClosed: client 1                   
ERROR: logging before flag.Parse: E1019 15:45:19.413315   25829 server.go:237] mysql_server caught panic:
runtime error: index out of range
/usr/lib/go/src/runtime/panic.go:513 (0x42f898)
	gopanic: reflectcall(nil, unsafe.Pointer(d.fn), deferArgs(d), uint32(d.siz), uint32(d.siz))
/usr/lib/go/src/runtime/panic.go:44 (0x42e6d9)
	panicindex: panic(indexError)
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan/group_by.go:397 (0x8d05fa)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan.evalBuffer: return buffer[0], nil
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan/group_by.go:376 (0x8d0205)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan.evalBuffers: val, err := evalBuffer(ctx, agg, buffers[i])
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan/group_by.go:212 (0x8cee20)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan.(*groupByIter).Next: return evalBuffers(i.ctx, i.buf, i.aggregate)
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/session.go:228 (0x7a045c)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql.(*spanIter).Next: row, err := i.iter.Next()
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan/limit.go:79 (0x8d34c4)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan.(*limitIter).Next: childRow, err := li.childIter.Next()
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/session.go:228 (0x7a045c)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql.(*spanIter).Next: row, err := i.iter.Next()
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan/process.go:145 (0x8d6086)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/sql/plan.(*trackedRowIter).Next: row, err := i.iter.Next()
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/server/handler.go:111 (0xc7344c)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-mysql-server.v0/server.(*Handler).ComQuery: row, err := rows.Next()
/home/jfontan/go/src/github.com/src-d/gitbase/vendor/gopkg.in/src-d/go-vitess.v1/mysql/server.go:417 (0xba83bb)
	com/src-d/gitbase/vendor/gopkg.in/src-d/go-vitess.v1/mysql.(*Listener).handle: err := l.handler.ComQuery(c, query, func(qr *sqltypes.Result) error {
/usr/lib/go/src/runtime/asm_amd64.s:1333 (0x45ccc0)
	goexit: BYTE	$0x90	// NOP

Repositories:

gopkg.in/src-d/core-retrieval.v0
gopkg.in/src-d/framework.v0
gopkg.in/src-d/go-billy-siva.v4
gopkg.in/src-d/go-billy.v4
gopkg.in/src-d/go-cli.v0
gopkg.in/src-d/go-errors.v0
gopkg.in/src-d/go-errors.v1
gopkg.in/src-d/go-git-fixtures.v3
gopkg.in/src-d/go-git.v4
gopkg.in/src-d/go-kallax.v1
gopkg.in/src-d/go-log.v0
gopkg.in/src-d/go-log.v1
gopkg.in/src-d/go-mysql-server.v0
gopkg.in/src-d/go-parse-utils.v1
gopkg.in/src-d/go-queue.v1
gopkg.in/src-d/go-siva.v1
gopkg.in/src-d/go-vitess.v0
gopkg.in/src-d/go-vitess.v1
gopkg.in/src-d/regression-core.v0

[kuba--]

It's also reproducible on the current master (042dd2ce) with pga repos:
pga list -l python -f json | head -n 10 | jq -r '.sivaFilenames[]' | pga get -i -o repos