sql: Internal Executor does not work properly with Virtual Index

[jackcwu]

Problem
When including the INDEX field when defining virtual schema tables in crdb_internal.go and calling it through a built-in, it causes a panic

To Reproduce

1. Apply this diff

diff --git a/pkg/sql/crdb_internal.go b/pkg/sql/crdb_internal.go
index 28502a8986..0ab8504bd0 100644
--- a/pkg/sql/crdb_internal.go
+++ b/pkg/sql/crdb_internal.go
@@ -2243,7 +2243,8 @@ CREATE TABLE crdb_internal.create_type_statements (
   descriptor_id      INT,
   descriptor_name    STRING,
   create_statement   STRING,
-  enum_members       STRING[] -- populated only for ENUM types
+  enum_members       STRING[], -- populated only for ENUM types
+INDEX (descriptor_id)
 )
 `,
     populate: func(ctx context.Context, p *planner, db catalog.DatabaseDescriptor, addRow func(...tree.Datum) error) error {

2. start a server
3. run create type greeting as enum ('hi');
4. run SHOW CREATE ALL TYPES;

Expected behavior
This should not panic since the enums are being properly populated

Additional data / screenshots

• ERROR: [n1,client=127.0.0.1:64058,hostssl,user=demo,intExec=crdb_internal.show_create_all_types] a panic has occurred!
• runtime error: index out of range [0] with length 0
• (1) attached stack trace
• -- stack trace:
• | runtime.gopanic
• | /usr/local/opt/go/libexec/src/runtime/panic.go:1038
• | runtime.goPanicIndex
• | /usr/local/opt/go/libexec/src/runtime/panic.go:90
• | github.com/cockroachdb/cockroach/pkg/sql.virtualSchemaTable.getIndex
• | /Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/sql/virtual_schema.go:220
• | github.com/cockroachdb/cockroach/pkg/sql.(*virtualDefEntry).makeConstrainedRowsGenerator.func1
• | /Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/sql/virtual_schema.go:628
• | github.com/cockroachdb/cockroach/pkg/sql.setupGenerator.func3
• | /Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/sql/virtual_table.go:120
• | github.com/cockroachdb/cockroach/pkg/util/stop.(*Stopper).RunAsyncTaskEx.func2
• | /Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/util/stop/stopper.go:491
• | runtime.goexit
• | /usr/local/opt/go/libexec/src/runtime/asm_amd64.s:1581
• Wraps: (2) runtime error: index out of range [0] with length 0
• Error types: (1) *withstack.withStack (2) runtime.boundsError

panic: runtime error: index out of range [0] with length 0 [recovered]
panic: runtime error: index out of range [0] with length 0

goroutine 7396 [running]:
github.com/cockroachdb/cockroach/pkg/util/stop.(*Stopper).Recover(0xc0009ec090, {0x99ef238, 0xc001288740})
/Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/util/stop/stopper.go:254 +0xaa
panic({0x80e4e40, 0xc001568360})
/usr/local/opt/go/libexec/src/runtime/panic.go:1038 +0x215
github.com/cockroachdb/cockroach/pkg/sql.virtualSchemaTable.getIndex(...)
/Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/sql/virtual_schema.go:220
github.com/cockroachdb/cockroach/pkg/sql.(*virtualDefEntry).makeConstrainedRowsGenerator.func1({0x99555e0, 0xc000674400})
/Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/sql/virtual_schema.go:628 +0x7f9
github.com/cockroachdb/cockroach/pkg/sql.setupGenerator.func3({0x99ef238, 0xc001288740})
/Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/sql/virtual_table.go:120 +0x130
github.com/cockroachdb/cockroach/pkg/util/stop.(*Stopper).RunAsyncTaskEx.func2()
/Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/util/stop/stopper.go:491 +0x12a
created by github.com/cockroachdb/cockroach/pkg/util/stop.(*Stopper).RunAsyncTaskEx
/Users/jackwu/go/src/github.com/cockroachdb/cockroach/pkg/util/stop/stopper.go:481 +0x445

Environment:

• CockroachDB version [e.g. 2.0.x]
• Server OS: [e.g. Linux/Distrib]
• Client app [e.g. cockroach sql, JDBC, ...]

Additional context
What was the impact?

Add any other context about the problem here.

[otan]

this isn't a bug - this is an unfinished implementation!

you need to also implement how a index works in this case:

cockroach/pkg/sql/virtual_schema.go

Line 110 in e08166a

indexes []virtualIndex

[rafiss]

looks like this actually was always broken since 0bcddba. (the INDEX was added without being implemented. there probably should be some validation that disallows that...)

confirmed that it's broken in 21.1, so i'm actually going to re-open this and fix.

root@:26257/defaultdb> create type mood as enum ('meh');
CREATE TYPE

root@:26257/defaultdb> select * from crdb_internal.create_type_statements where descriptor_id=123;
ERROR: driver: bad connection
warning: connection lost!

[otan]

ooof