Prevent concurrent table creation errors for long metric name

Previously, when two metrics with really long names were created
concurrently, postgres could throw errors due to name collision
violations when it created constraint names as well as type names
for the type corresponding to the table.

Constraint names was fixed by explicitly assigning a unique constraint
name instead of having PG autogenerate one.

Types are a bit trickier. Turns out for every table X, PG assigns
an array type '_X' (makeArrayTypeName() in PG source). That can
also collide and cause erroors. The fix was for us to change the
max length of the table names we geneate from 63 chars to 62 chars,
thus reserving one char for the underscore.

pkg/pgmodel/end_to_end_tests/concurrent_sql_test.go

@@ -6,6 +6,7 @@ package end_to_end_tests
 import (
 	"context"
 	"fmt"
+	"strings"
 	"sync"
 	"testing"
 
@@ -135,21 +136,50 @@ func TestConcurrentSQL(t *testing.T) {
 				t.Fatalf("ids aren't equal: %d != %d", id1, id2)
 			}
 
-			wg.Add(2)
+			/* test creating tables with same long name */
+			wg.Add(3)
+			go func() {
+				defer wg.Done()
+				_, err := db.Exec(context.Background(), "CALL _prom_catalog.finalize_metric_creation()")
+				if err != nil {
+					t.Fatal(err)
+				}
+			}()
+			metric := fmt.Sprintf("test1"+strings.Repeat("long_name_", 10)+"goc_metric_%d", i)
 			go func() {
 				defer wg.Done()
-				id1 = testConcurrentGOCMetricTable(t, db, fmt.Sprintf("goc_metric_%d", i))
+				id1 = testConcurrentGOCMetricTable(t, db, metric)
 			}()
 			go func() {
 				defer wg.Done()
-				id2 = testConcurrentGOCMetricTable(t, db, fmt.Sprintf("goc_metric_%d", i))
+				id2 = testConcurrentGOCMetricTable(t, db, metric)
 			}()
 			wg.Wait()
 
 			if id1 != id2 {
 				t.Fatalf("ids aren't equal: %d != %d", id1, id2)
 			}
 
+			/* test creating tables with long names and different suffixes */
+			wg.Add(3)
+			go func() {
+				defer wg.Done()
+				_, err := db.Exec(context.Background(), "CALL _prom_catalog.finalize_metric_creation()")
+				if err != nil {
+					t.Fatal(err)
+				}
+			}()
+			metric = fmt.Sprintf("test2"+strings.Repeat("long_name_", 10)+"goc_metric_%d", i)
+			go func() {
+				defer wg.Done()
+				id1 = testConcurrentGOCMetricTable(t, db, metric)
+			}()
+			go func() {
+				defer wg.Done()
+				id2 = testConcurrentGOCMetricTable(t, db, metric+"_diff")
+			}()
+			wg.Wait()
+
 			wg.Add(2)
 			go func() {
 				defer wg.Done()

pkg/pgmodel/migrations/sql/1_base_schema.up.sql

@@ -282,8 +282,8 @@ BEGIN
             labels SCHEMA_PROM.label_array NOT NULL,
             CHECK(labels[1] = %2$L AND labels[1] IS NOT NULL),
             CHECK(metric_id = %3$L),
-            UNIQUE(labels) INCLUDE (id),
-            PRIMARY KEY(id)
+            CONSTRAINT series_labels_id_%3$s UNIQUE(labels) INCLUDE (id),
+            CONSTRAINT series_pkey_%3$s PRIMARY KEY(id)
         )
     $$, NEW.table_name, label_id, NEW.id);
 
@@ -307,12 +307,12 @@ CREATE TRIGGER make_metric_table_trigger
 
 -- Return a table name built from a full_name and a suffix.
 -- The full name is truncated so that the suffix could fit in full.
--- name size will always be exactly 63 chars.
+-- name size will always be exactly 62 chars.
 CREATE OR REPLACE FUNCTION SCHEMA_CATALOG.pg_name_with_suffix(
         full_name text, suffix text)
     RETURNS name
 AS $func$
-    SELECT (substring(full_name for 63-(char_length(suffix)+1)) || '_' || suffix)::name
+    SELECT (substring(full_name for 62-(char_length(suffix)+1)) || '_' || suffix)::name
 $func$
 LANGUAGE SQL IMMUTABLE PARALLEL SAFE;
 GRANT EXECUTE ON FUNCTION SCHEMA_CATALOG.pg_name_with_suffix(text, text) TO prom_reader;
@@ -322,14 +322,18 @@ GRANT EXECUTE ON FUNCTION SCHEMA_CATALOG.pg_name_with_suffix(text, text) TO prom
 -- full name doesn't fit, generates a new unique name.
 -- Note that there cannot be a collision betweeen a user
 -- defined name and a name with a suffix because user
--- defined names of length 63 always get a suffix and
--- conversely, all names with a suffix are length 63.
+-- defined names of length 62 always get a suffix and
+-- conversely, all names with a suffix are length 62.
+
+-- We use a max name length of 62 not 63 because table creation creates an
+-- array type named `_tablename`. We need to ensure that this name is
+-- unique as well, so have to reserve a space for the underscore.
 CREATE OR REPLACE FUNCTION SCHEMA_CATALOG.pg_name_unique(
         full_name_arg text, suffix text)
     RETURNS name
 AS $func$
     SELECT CASE
-        WHEN char_length(full_name_arg) < 63 THEN
+        WHEN char_length(full_name_arg) < 62 THEN
             full_name_arg::name
         ELSE
             SCHEMA_CATALOG.pg_name_with_suffix(

pkg/pgmodel/pgx.go

@@ -372,6 +372,10 @@ func (p *pgxInserter) createMetricTable(metric string) (string, error) {
 	var tableName string
 	defer res.Close()
 	if !res.Next() {
+		err = res.Err()
+		if err != nil {
+			return "", err
+		}
 		return "", errMissingTableName
 	}