sql/hints: add tests for statement hints cache

This commit adds a set of tests for the behavior of the hint cache.
The tests verify that the cache is correctly populated in response
to existing hints as well as new insertions and deletions.

Epic: None

Release note: None

Author: DrewKimball

pkg/BUILD.bazel

@@ -506,6 +506,7 @@ ALL_TESTS = [
     "//pkg/sql/gcjob/gcjobnotifier:gcjobnotifier_test",
     "//pkg/sql/gcjob:gcjob_test",
     "//pkg/sql/gcjob_test:gcjob_test_test",
+    "//pkg/sql/hints:hints_test",
     "//pkg/sql/idxrecommendations:idxrecommendations_test",
     "//pkg/sql/idxusage:idxusage_test",
     "//pkg/sql/importer:importer_test",
@@ -2066,6 +2067,7 @@ GO_TARGETS = [
     "//pkg/sql/gcjob:gcjob_test",
     "//pkg/sql/gcjob_test:gcjob_test_test",
     "//pkg/sql/hints:hints",
+    "//pkg/sql/hints:hints_test",
     "//pkg/sql/idxrecommendations:idxrecommendations",
     "//pkg/sql/idxrecommendations:idxrecommendations_test",
     "//pkg/sql/idxusage:idxusage",

pkg/sql/hints/BUILD.bazel

@@ -1,6 +1,6 @@
 load("@rules_proto//proto:defs.bzl", "proto_library")
 load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
-load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "hints",
@@ -59,3 +59,32 @@ proto_library(
     visibility = ["//visibility:public"],
     deps = ["@com_github_gogo_protobuf//gogoproto:gogo_proto"],
 )
+
+go_test(
+    name = "hints_test",
+    srcs = [
+        "hint_cache_test.go",
+        "main_test.go",
+    ],
+    deps = [
+        ":hints",
+        "//pkg/base",
+        "//pkg/kv/kvclient/rangefeed",
+        "//pkg/security/securityassets",
+        "//pkg/security/securitytest",
+        "//pkg/server",
+        "//pkg/sql/catalog",
+        "//pkg/sql/catalog/descs",
+        "//pkg/sql/randgen",
+        "//pkg/sql/stats",
+        "//pkg/testutils",
+        "//pkg/testutils/serverutils",
+        "//pkg/testutils/sqlutils",
+        "//pkg/testutils/testcluster",
+        "//pkg/util/leaktest",
+        "//pkg/util/log",
+        "//pkg/util/randutil",
+        "@com_github_cockroachdb_errors//:errors",
+        "@com_github_stretchr_testify//require",
+    ],
+)

pkg/sql/hints/hint_cache.go

@@ -68,6 +68,12 @@ type StatementHintsCache struct {
 		// system.statement_hints table. Cached hints are never modified after being
 		// added to the cache, and so can be returned directly without copying.
 		hintCache *cache.UnorderedCache
+
+		// Used for testing; keeps track of how many times we actually read hints
+		// from the system table. Note that this count only includes reads used for
+		// hintCache, not for hintedHashes.
+		// TODO(drewk): consider making this a metric.
+		numInternalQueries int
 	}
 
 	// Used to start/coordinate the rangefeed.
@@ -445,6 +451,7 @@ func (c *StatementHintsCache) addCacheEntryLocked(
 		waitCond: sync.Cond{L: &c.mu},
 	}
 	c.mu.hintCache.Add(statementHash, entry)
+	c.mu.numInternalQueries++
 
 	var err error
 	func() {
@@ -535,3 +542,31 @@ func (entry *cacheEntry) getMatchingHints(statementFingerprint string) []Stateme
 	}
 	return res
 }
+
+// ============================================================================
+// Test helpers.
+// ============================================================================
+
+// TestingHashCount returns the number of hashes with hints.
+func (c *StatementHintsCache) TestingHashCount() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return len(c.mu.hintedHashes)
+}
+
+// TestingHashHasHints returns true if the given hash has any hints, and false
+// otherwise.
+func (c *StatementHintsCache) TestingHashHasHints(hash int64) bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	_, hasHints := c.mu.hintedHashes[hash]
+	return hasHints
+}
+
+// TestingNumTableReads returns the number of times hints have been read from
+// the system.statement_hints table.
+func (c *StatementHintsCache) TestingNumTableReads() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.mu.numInternalQueries
+}