Crash on BEFORE INSERT trigger using DECLARE variable

[0x4261756D]

When inserting into a table that has a before-insert trigger with a DECLARE variable in its body the dolt server crashes.

My trigger:

CREATE TRIGGER foo BEFORE INSERT ON PartNumber
BEGIN
  DECLARE newmax VARCHAR(255);
  SELECT CONCAT('A', MAX(CAST(SUBSTRING(UniqueID, 2) AS UNSIGNED)) + 1) INTO newmax FROM PartNumber;
  SET NEW.UniqueId = newmax;
END;

A simpler version that produces the same crash:

CREATE TRIGGER foo BEFORE INSERT ON PartNumber
BEGIN
  DECLARE newmax VARCHAR(255);
  SET newmax = 'FOO';
  SET NEW.UniqueID = newmax;
END;

Crashlog:

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x0 pc=0x16be072]

goroutine 1256 [running]:
github.com/dolthub/go-mysql-server/sql/expression.(*ProcedureReference).InitializeVariable(0x0, {0xc0024313e8, 0x6}, {0x37b8910, 0xc0023f2e40}, {0x0?, 0x0?})
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/expression/procedurereference.go:68 +0xf2
github.com/dolthub/go-mysql-server/sql/rowexec.(*declareVariablesIter).Next(0xc0007863a0, 0x1f755924c30?)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/rel_iters.go:736 +0xbe
github.com/dolthub/go-mysql-server/sql/rowexec.(*triggerBlockIter).Next(0xc000b23500, 0xc000a759a0)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/dml_iters.go:103 +0x202
github.com/dolthub/go-mysql-server/sql/rowexec.(*triggerIter).Next(0xc0023b4410, 0x0?)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/dml_iters.go:217 +0x30f
github.com/dolthub/go-mysql-server/sql/rowexec.(*insertIter).Next(0xc0025125b0, 0xc000d5b0e0)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/insert.go:63 +0x3e
github.com/dolthub/go-mysql-server/sql/plan.(*TableEditorIter).Next(0xc0023b4460, 0xc000d5b0e0)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/plan/table_editor.go:55 +0x72
github.com/dolthub/go-mysql-server/sql/rowexec.(*accumulatorIter).Next(0xc000523770, 0xc000d5b0e0)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/dml_iters.go:513 +0x1f7
github.com/dolthub/go-mysql-server/sql/rowexec.(*triggerRollbackIter).Next(0xc000107a70, 0xc000d5b0e0)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/dml_iters.go:37 +0x3d
github.com/dolthub/go-mysql-server/sql/rowexec.transactionCommittingIter.Next(...)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/rowexec/transaction_iters.go:78
github.com/dolthub/go-mysql-server/sql/plan.(*trackedRowIter).Next(0xc000b23440, 0xc00010f8c0?)
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/sql/plan/process.go:357 +0x24
github.com/dolthub/go-mysql-server/server.(*Handler).doQuery.func2()
	C:/Users/User/go/pkg/mod/github.com/dolthub/go-mysql-server@v0.18.1-0.20240405190351-4baf7c65a6db/server/handler.go:425 +0x124
golang.org/x/sync/errgroup.(*Group).Go.func1()
	C:/Users/User/go/pkg/mod/golang.org/x/sync@v0.6.0/errgroup/errgroup.go:78 +0x56
created by golang.org/x/sync/errgroup.(*Group).Go in goroutine 186
	C:/Users/User/go/pkg/mod/golang.org/x/sync@v0.6.0/errgroup/errgroup.go:75 +0x96

[jycor]

Hey @0x4261756D, thanks for reporting this issue!

Triggers are a tricky area for us, but we are looking into it.
For now, we have it so that triggers like this won't panic.

[jycor]

Hey @0x4261756D, the fix for this has been merged to dolt main.

DECLAREs should work just fine in triggers.
While fixing this issue, we discovered #7737 .
So, just don't call external stored procedures in your triggers, and it should be fine.

A release with the fix should be out soon.