Do not allocate internal keys in top memory context

Since all places which use the keys first copy them into long-lived
memory we do not need to do that when allocating.

contrib/pg_tde/src/access/pg_tde_tdemap.c

@@ -123,6 +123,7 @@ RelKeyCache tde_rel_key_cache = {
 static WALKeyCacheRec *tde_wal_key_cache = NULL;
 static WALKeyCacheRec *tde_wal_key_last_rec = NULL;
 
+static InternalKey *pg_tde_get_key_from_file(const RelFileLocator *rlocator, uint32 key_type, bool no_map_ok);
 static int32 pg_tde_process_map_entry(const RelFileLocator *rlocator, uint32 key_type, char *db_map_path, off_t *offset, bool should_delete);
 static InternalKey *pg_tde_read_keydata(char *db_keydata_path, int32 key_index, TDEPrincipalKey *principal_key);
 static InternalKey *tde_decrypt_rel_key(TDEPrincipalKey *principal_key, InternalKey *enc_rel_key_data, Oid dbOid);
@@ -978,12 +979,11 @@ pg_tde_wal_last_key_set_lsn(XLogRecPtr lsn, const char *keyfile_path)
  * Reads the key of the required relation. It identifies its map entry and then simply
  * reads the key data from the keydata file.
  */
-InternalKey *
+static InternalKey *
 pg_tde_get_key_from_file(const RelFileLocator *rlocator, uint32 key_type, bool no_map_ok)
 {
 	int32		key_index = 0;
 	TDEPrincipalKey *principal_key;
-	InternalKey *rel_key_data;
 	InternalKey *enc_rel_key_data;
 	off_t		offset = 0;
 	LWLock	   *lock_pk = tde_lwlock_enc_keys();
@@ -1037,9 +1037,7 @@ pg_tde_get_key_from_file(const RelFileLocator *rlocator, uint32 key_type, bool n
 	enc_rel_key_data = pg_tde_read_keydata(db_keydata_path, key_index, principal_key);
 	LWLockRelease(lock_pk);
 
-	rel_key_data = tde_decrypt_rel_key(principal_key, enc_rel_key_data, rlocator->dbOid);
-
-	return rel_key_data;
+	return tde_decrypt_rel_key(principal_key, enc_rel_key_data, rlocator->dbOid);
 }
 
 /*

contrib/pg_tde/src/encryption/enc_tde.c

@@ -1,7 +1,6 @@
 #include "pg_tde_defines.h"
 
 #include "postgres.h"
-#include "utils/memutils.h"
 
 #include "access/pg_tde_tdemap.h"
 #include "encryption/enc_tde.h"
@@ -194,25 +193,13 @@ AesDecryptKey(const TDEPrincipalKey *principal_key, Oid dbOid, InternalKey **p_r
 {
 	unsigned char iv[16] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
 
-#ifndef FRONTEND
-	MemoryContext oldcontext;
-#endif
-
 	/* Ensure we are getting a valid pointer here */
 	Assert(principal_key);
 
 	memcpy(iv, &dbOid, sizeof(Oid));
 
-#ifndef FRONTEND
-	oldcontext = MemoryContextSwitchTo(TopMemoryContext);
-#endif
-
 	*p_rel_key_data = (InternalKey *) palloc(sizeof(InternalKey));
 
-#ifndef FRONTEND
-	MemoryContextSwitchTo(oldcontext);
-#endif
-
 	/* Fill in the structure */
 	memcpy(*p_rel_key_data, enc_rel_key_data, sizeof(InternalKey));
 	(*p_rel_key_data)->ctx = NULL;

contrib/pg_tde/src/include/access/pg_tde_tdemap.h

@@ -108,7 +108,6 @@ extern TDEPrincipalKeyInfo *pg_tde_get_principal_key_info(Oid dbOid);
 extern bool pg_tde_save_principal_key(TDEPrincipalKeyInfo *principal_key_info, bool truncate_existing, bool update_header);
 extern bool pg_tde_perform_rotate_key(TDEPrincipalKey *principal_key, TDEPrincipalKey *new_principal_key);
 extern bool pg_tde_write_map_keydata_files(off_t map_size, char *m_file_data, off_t keydata_size, char *k_file_data);
-extern InternalKey *pg_tde_get_key_from_file(const RelFileLocator *rlocator, uint32 key_type, bool no_map_ok);
 
 const char *tde_sprint_key(InternalKey *k);