Improve function naming for getting jsonb and label value

Change function names to val() and jsonb() for getting
the label value from an id and the jsonb from a label array.

Change the type name for a label array from label_ids to
label_array for consistency.

Fix places where a connection pool was started before a
migration to start after. This doen't work if a migration alters
database to change gucs because pool connection started before
the migrate won't pick up the change. This lead to test flakiness
and could produce real bugs too.

cmd/timescale-prometheus/main.go

@@ -137,19 +137,22 @@ func main() {
 
 	http.Handle(cfg.telemetryPath, promhttp.Handler())
 
+	elector = initElector(cfg)
+
+	// migrate has to happen after elector started
+	if cfg.migrate {
+		migrate(&cfg.pgmodelCfg)
+	}
+
+	// client has to be initiated after migrate since migrate
+	// can change database GUC settings
 	client, err := pgclient.NewClient(&cfg.pgmodelCfg)
 	if err != nil {
 		log.Error(err)
 		os.Exit(1)
 	}
 	defer client.Close()
 
-	elector = initElector(cfg)
-
-	if cfg.migrate {
-		migrate(&cfg.pgmodelCfg)
-	}
-
 	http.Handle("/write", timeHandler("write", write(client)))
 	http.Handle("/read", timeHandler("read", read(client)))
 	http.Handle("/healthz", health(client))

docs/sql_schema.md

@@ -24,8 +24,8 @@ simply `cpu_usage` view). The view contains a the following column:
  - labels - The array of label ids
  - plus a column for each label name's id in the metric's label set
 
-A label value can be retrieved from the label name id using the `get_label_value`
-function. A full json for the series can be retrieved with `label_array_to_jsonb(labels)`.
+A label value can be retrieved from the label name id using the `val`
+function. A full json for the series can be retrieved with `jsonb(labels)`.
 
 For example:
 ```
@@ -42,12 +42,15 @@ For example:
 ```
 
 Example query for single point with their labels:
+
+```
 SELECT
-    label_array_to_jsonb(labels) as labels,
+    jsonb(labels) as labels,
     value
 FROM cpu_usage
 WHERE time < now();
-
+```
+Results:
 ```
                      labels                   | value
 ----------------------------------------------+-------
@@ -59,12 +62,15 @@ WHERE time < now();
 
 Example query for a rollup:
 
+```
 SELECT
-   get_label_value(node_id) as node,
+   val(node_id) as node,
    avg(value)
 FROM cpu_usage
 WHERE time < now()
 GROUP BY node_id
+```
+Results:
 
 ```
  node  | avg
@@ -143,7 +149,7 @@ FROM cpu_usage  u
 WHERE labels ? ('namepace' == 'dev') AND labels ? ('node' == 'brain')
 ```
 
-Label matchers are formed by using a qualifier of the form `labels ? (<tag_key> <operator> <pattern>)`.
+Label matchers are formed by using a qualifier of the form `labels ? (<tag_key> <operator> <pattern>)` (note: the parantheses are mandatory).
 There are four operators,
 
 - `==` match tag values that are equal to the pattern
@@ -165,7 +171,7 @@ For those coming from PromQL there are a few differences to keep in mind:
 
 The `eq` function tests exact equivalence between labels, without comparing the metric name (`__name__`) label key.
 For instance if the labels `a` is `{"__name__":"metric", "foo":"bar", "baz":"frob"}`
-then `SELECT eq(a, jsonb {"__name__":"something else", "foo":"bar", "baz":"frob"})` will evaluate to `true`, however, unlike `@>` if `SELECT eq(a, {"__name__":"metric", "foo":"bar"})` will evaluate to `false`.
+then `SELECT eq(a, jsonb {"__name__":"something else", "foo":"bar", "baz":"frob"})` will evaluate to `true`, however, unlike `@>`, the query `SELECT eq(a, {"__name__":"metric", "foo":"bar"})` will evaluate to `false`.
 Thus, it can be used to compare across metrics or within a metric.
 
 For example, to join 2 series that are scraped at the same time:

pkg/pgmodel/migrate_test.go

@@ -412,6 +412,15 @@ func TestSQLRetentionPeriod(t *testing.T) {
 	})
 }
 
+func getFingerprintFromJson(t *testing.T, jsonRes []byte) model.Fingerprint {
+	labelSetRes := make(model.LabelSet)
+	err := json.Unmarshal(jsonRes, &labelSetRes)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return labelSetRes.Fingerprint()
+}
+
 func TestSQLJsonLabelArray(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping integration test")
@@ -548,7 +557,7 @@ func TestSQLJsonLabelArray(t *testing.T) {
 						t.Fatal(err)
 					}
 					var labelArray []int
-					err = db.QueryRow(context.Background(), "SELECT * FROM prom.jsonb_to_label_array($1)", jsonOrig).Scan(&labelArray)
+					err = db.QueryRow(context.Background(), "SELECT * FROM prom.label_array($1)", jsonOrig).Scan(&labelArray)
 					if err != nil {
 						t.Fatal(err)
 					}
@@ -575,18 +584,14 @@ func TestSQLJsonLabelArray(t *testing.T) {
 						t.Fatalf("Expected label arrays to be equal: %v != %v", labelArray, labelArrayKV)
 					}
 
-					var jsonres []byte
-					err = db.QueryRow(context.Background(), "SELECT * FROM prom.label_array_to_jsonb(($1::int[]))", labelArray).Scan(&jsonres)
+					var jsonRes []byte
+					err = db.QueryRow(context.Background(), "SELECT * FROM jsonb(($1::int[]))", labelArray).Scan(&jsonRes)
 					if err != nil {
 						t.Fatal(err)
 					}
-					labelSetRes := make(model.LabelSet, len(ts.Labels))
-					err = json.Unmarshal(jsonres, &labelSetRes)
-					if err != nil {
-						t.Fatal(err)
-					}
-					if labelSet.Fingerprint() != labelSetRes.Fingerprint() {
-						t.Fatalf("Json not equal: got\n%v\nexpected\n%v", string(jsonres), string(jsonOrig))
+					fingerprintRes := getFingerprintFromJson(t, jsonRes)
+					if labelSet.Fingerprint() != fingerprintRes {
+						t.Fatalf("Json not equal: got\n%v\nexpected\n%v", string(fingerprintRes), string(jsonOrig))
 
 					}
 
@@ -626,19 +631,15 @@ func TestSQLJsonLabelArray(t *testing.T) {
 						t.Fatalf("Expected the series ids to be equal: %v != %v", seriesID, seriesIDKeyVal)
 					}
 
-					err = db.QueryRow(context.Background(), "SELECT prom.label_array_to_jsonb(labels) FROM _prom_catalog.series WHERE id=$1",
-						seriesID).Scan(&jsonres)
-					if err != nil {
-						t.Fatal(err)
-					}
-					labelSetRes = make(model.LabelSet, len(ts.Labels))
-					err = json.Unmarshal(jsonres, &labelSetRes)
+					err = db.QueryRow(context.Background(), "SELECT prom.jsonb(labels) FROM _prom_catalog.series WHERE id=$1",
+						seriesID).Scan(&jsonRes)
 					if err != nil {
 						t.Fatal(err)
 					}
+					fingerprintRes = getFingerprintFromJson(t, jsonRes)
 
-					if labelSet.Fingerprint() != labelSetRes.Fingerprint() {
-						t.Fatalf("Json not equal: got\n%v\nexpected\n%v", string(jsonres), string(jsonOrig))
+					if labelSet.Fingerprint() != fingerprintRes {
+						t.Fatalf("Json not equal: got\n%v\nexpected\n%v", string(jsonRes), string(jsonOrig))
 
 					}
 
@@ -1099,6 +1100,15 @@ func TestMain(m *testing.M) {
 func withDB(t testing.TB, DBName string, f func(db *pgxpool.Pool, t testing.TB)) {
 	testhelpers.WithDB(t, DBName, func(db *pgxpool.Pool, t testing.TB, connectURL string) {
 		performMigrate(t, DBName, connectURL)
+
+		//need to get a new pool after the Migrate to catch any GUC changes made during Migrate
+		db, err := pgxpool.Connect(context.Background(), connectURL)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer func() {
+			db.Close()
+		}()
 		f(db, t)
 	})
 }