perf(plan): cache bounded legacy TEXT syntax evidence

pkg/sql/plan/legacy_tinytext.go

@@ -106,7 +106,7 @@ func recoverLegacyTinyText(
 	if !containsLegacyTextFamily(lowerCreateSQL) && !strings.Contains(lowerCreateSQL, "like") {
 		return nil
 	}
-	evidence, err := parseLegacyTinyTextEvidence(ctx, tableDef.Createsql)
+	evidence, err := parseCachedLegacyTinyTextEvidence(ctx, tableDef.Createsql)
 	if err != nil {
 		return nil
 	}

pkg/sql/plan/legacy_tinytext_cache.go

@@ -0,0 +1,113 @@
+// Copyright 2026 Matrix Origin
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package plan
+
+import (
+	"context"
+	"strings"
+	"sync"
+)
+
+const (
+	legacyTextCacheEntries    = 32
+	legacyTextCacheSQLBytes   = 16 << 10
+	legacyTextCacheColumns    = 256
+	legacyTextCacheEntryBytes = 64 << 10
+)
+
+type legacyTextParseCacheEntry struct {
+	createSQL string
+	evidence  legacyTinyTextCreateEvidence
+}
+
+// Cache syntax evidence only. Identity, Seqnum and CREATE LIKE resolution must
+// still be checked against the current transaction on every recovery. Entries
+// own detached immutable strings/slices, never ASTs or catalog definitions.
+// Round-robin eviction bounds retained payload to 2MiB plus fixed headers.
+type legacyTextParseCache struct {
+	mu      sync.RWMutex
+	entries [legacyTextCacheEntries]legacyTextParseCacheEntry
+	next    int
+}
+
+var legacyTextEvidenceCache legacyTextParseCache
+
+func (cache *legacyTextParseCache) get(createSQL string) (legacyTinyTextCreateEvidence, bool) {
+	if len(createSQL) == 0 || len(createSQL) > legacyTextCacheSQLBytes {
+		return legacyTinyTextCreateEvidence{}, false
+	}
+	cache.mu.RLock()
+	defer cache.mu.RUnlock()
+	for _, entry := range cache.entries {
+		if entry.createSQL == createSQL {
+			return entry.evidence, true
+		}
+	}
+	return legacyTinyTextCreateEvidence{}, false
+}
+
+func (cache *legacyTextParseCache) put(createSQL string, evidence legacyTinyTextCreateEvidence) {
+	if len(createSQL) == 0 || len(createSQL) > legacyTextCacheSQLBytes || len(evidence.columns) > legacyTextCacheColumns {
+		return
+	}
+	// The conservative per-column allowance includes the slice element storage.
+	remaining := legacyTextCacheEntryBytes - len(createSQL) - 64*len(evidence.columns)
+	for _, text := range []string{evidence.likeDB, evidence.likeName} {
+		if len(text) > remaining {
+			return
+		}
+		remaining -= len(text)
+	}
+	for _, column := range evidence.columns {
+		if len(column.name) > remaining {
+			return
+		}
+		remaining -= len(column.name)
+	}
+
+	owned := legacyTinyTextCreateEvidence{
+		likeDB: strings.Clone(evidence.likeDB), likeName: strings.Clone(evidence.likeName),
+	}
+	if evidence.columns != nil {
+		owned.columns = make([]legacyTinyTextColumn, len(evidence.columns))
+		copy(owned.columns, evidence.columns)
+		for i := range owned.columns {
+			owned.columns[i].name = strings.Clone(owned.columns[i].name)
+		}
+	}
+	key := strings.Clone(createSQL)
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+	// Concurrent misses parse independently outside the lock. Do not evict an
+	// unrelated entry when another caller has already stored the same evidence.
+	for _, entry := range cache.entries {
+		if entry.createSQL == createSQL {
+			return
+		}
+	}
+	cache.entries[cache.next] = legacyTextParseCacheEntry{createSQL: key, evidence: owned}
+	cache.next = (cache.next + 1) % len(cache.entries)
+}
+
+func parseCachedLegacyTinyTextEvidence(ctx context.Context, createSQL string) (legacyTinyTextCreateEvidence, error) {
+	if evidence, ok := legacyTextEvidenceCache.get(createSQL); ok {
+		return evidence, nil
+	}
+	evidence, err := parseLegacyTinyTextEvidence(ctx, createSQL)
+	if err == nil {
+		legacyTextEvidenceCache.put(createSQL, evidence)
+	}
+	return evidence, err
+}