sql: fix gist decoding in foreign DB

When a gist is exported and decoded in a foreign DB it should still
decode w/o panic. If a table scan result columns are fed into a
group by column the group by column code expects the result columns to
be in tact and panics. Fix this by making fake "unknown" result columns
so we can print the plan.

Making this change led to an unintended change in gists_tpce, this is
because the catalog was shared between the test files and I added a
table.  Fix this for the future by creating a new catalog for each file.
But with this change the table ids encoded in the gists_tpce got
smaller.

Epic: None
Fixes: #110964
Release note (bug fix): Fixed panic when decoding gist in DB without the
table referred to by the gist.

pkg/sql/opt/exec/explain/plan_gist_test.go

@@ -118,6 +118,8 @@ func TestPlanGistBuilder(t *testing.T) {
 	}
 	// RFC: should I move this to opt_tester?
 	datadriven.RunTest(t, datapathutils.TestDataPath(t, "gists"), testGists)
+	// Reset the catalog for the next test.
+	catalog = testcat.New()
 	datadriven.RunTest(t, datapathutils.TestDataPath(t, "gists_tpce"), testGists)
 }
 

pkg/sql/opt/exec/explain/result_columns.go

@@ -11,6 +11,8 @@
 package explain
 
 import (
+	"fmt"
+
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/colinfo"
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/descpb"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/cat"
@@ -255,6 +257,12 @@ func tableColumns(table cat.Table, ordinals exec.TableColumnOrdinalSet) colinfo.
 				Name: string(col.ColName()),
 				Typ:  col.DatumType(),
 			})
+		} else {
+			// Give downstream operators something to chew on so that they don't panic.
+			cols = append(cols, colinfo.ResultColumn{
+				Name: fmt.Sprintf("unknownCol-%d", i),
+				Typ:  types.Unknown,
+			})
 		}
 	}
 	return cols

pkg/sql/opt/exec/explain/testdata/gists

@@ -1122,3 +1122,47 @@ explain(shape):
   syntax: "select 123"
 explain(gist):
 • show completions
+
+exec-ddl
+CREATE TABLE ts (a int, b STRING)
+----
+
+gist-explain-roundtrip
+SELECT max(a), b FROM ts WHERE a = 1 AND b LIKE '$ internal%' GROUP BY b
+----
+hash: 6959966538333657501
+plan-gist: AgF0AgADAAAAAwsCBgQ=
+explain(shape):
+• group (hash)
+│ group by: b
+│
+└── • filter
+    │ filter: (a = _) AND (b LIKE _)
+    │
+    └── • scan
+          table: ts@ts_pkey
+          spans: FULL SCAN
+explain(gist):
+• group (hash)
+│ group by: a
+│
+└── • filter
+    │
+    └── • scan
+          table: ts@ts_pkey
+          spans: FULL SCAN
+
+# The above query produces this gist when run via EXPLAIN (GIST) in a real DB and when
+# run in a DB w/o that table panics, this tests that the panic is fixed.  Essentially we're
+# exercising the "unknown" table code.
+explain-plan-gist
+AgHQAQIAAwAAAAMLAgYE
+----
+• group (hash)
+│ group by: unknownCol-0
+│
+└── • filter
+    │
+    └── • scan
+          table: ?@?
+          spans: FULL SCAN

pkg/sql/opt/exec/explain/testdata/gists_tpce

@@ -22,7 +22,7 @@ GROUP BY b_name
 ORDER BY 2 DESC
 ----
 hash: 14732118561700026222
-plan-gist: AgGUAQQAPAAAAAGqAQQAAwIAABQAogEEAgAUAJgBBAIAFACsAQQCAAkAAgIAARQAhgECAgEHBAsCBwQRBgQ=
+plan-gist: AgGKAQQAPAAAAAGgAQQAAwIAABQAmAEEAgAUAI4BBAIAFACiAQQCAAkAAgIAARQAfAICAQcECwIHBBEGBA==
 explain(shape):
 • sort
 │ order: -sum
@@ -116,7 +116,7 @@ LEFT JOIN last_trade      ON lt_s_symb = hs_s_symb
     LIMIT 10;
 ----
 hash: 10378570089558454947
-plan-gist: AgF4BAAFAgAAE3gCFAGAAQICABQBpAECAgEHBgsCBwYYBgY=
+plan-gist: AgFuBAAFAgAAE24CFAF2AgIAFAGaAQICAQcGCwIHBhgGBg==
 explain(shape):
 • top-k
 │ order: +"coalesce"
@@ -211,7 +211,7 @@ update_trade_submitted AS (
 SELECT * FROM request_list;
 ----
 hash: 7096273538769246907
-plan-gist: AgGkAQIAHwIAAAcQBRAhpAEAAAcCMAGUAQIAHwAAAAMHCDAxBQIUAJQBAgIBBQgHCAUII5QBAAcCMDEFAgcGBQYwH5IBADEFAhQFkAECAgEqMQUCFAWwAQICASoHAjAxBQIUAJABAgIBBRwHIAUgMCGQAQAAMQUCFAWwAQICASoHAjAxBQgGCA==
+plan-gist: AgGaAQIAHwIAAAcQBRAhmgEAAAcCMAGKAQIAHwAAAAMHCDAxBQIUAIoBAgIBBQgHCAUII4oBAAcCMDEFAgcGBQYwH4gBADEFAhQFhgECAgEqMQUCFAWmAQICASoHAjAxBQIUAIYBAgIBBRwHIAUgMCGGAQAAMQUCFAWmAQICASoHAjAxBQgGCA==
 explain(shape):
 • root
 │