lua: clear page-in fingerprint TLS at each inner statement's true end

Lua stored-procedure inner statements (db:exec/db:prepare, temp table
handling) already set the page-in fingerprint thread-local correctly
via the shared get_prepared_stmt_int() chokepoint, but had no
per-inner-statement clear -- only the whole-procedure sqlite_done()
call cleared it. This let page-ins between one inner statement
finishing and the next one's own prepare bleed onto the previous
statement's fingerprint instead of falling into NO-FINGERPRINT.

Adds bdb_fingerprint_rtstats_clear() at every point an inner
statement's execution conclusively ends: donate_stmt() (the shared
terminal disposal point for exec/prepare/cursor handles -- covers
dbstmt_free, dbstmt_exec's error path, dbstmt_fetch exhaustion,
dbstmt_close, and reset_stmt's terminal branch) plus the six direct
sqlite3_finalize() sites that bypass it (create_temp_table,
dbtable_insert, dbtable_copyfrom, db_csvcopy, drop_temp_tables,
clone_temp_tables). Deliberately does not hook lua_end_step(), since
it fires multiple times against the same open statement in some paths
(db_csvcopy, once per CSV row) and would clear prematurely.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Signed-off-by: Mark Hannum <mhannum@bloomberg.net>

Author: markhannum

lua/sp.c

@@ -1146,6 +1146,8 @@ static void donate_stmt(SP sp, dbstmt_t *dbstmt)
     sqlite3_stmt *stmt = dbstmt->stmt;
     if (stmt == NULL) return;
 
+    bdb_fingerprint_rtstats_clear();
+
     if (!gbl_enable_sql_stmt_caching || !dbstmt->rec) {
         sqlite3_finalize(stmt);
     } else {
@@ -1249,6 +1251,7 @@ static struct sp_tmptbl *create_temp_table(Lua lua, const char **name)
     }
     lua_end_step(sp->clnt, sp, stmt);
     set_tmptbl(NULL);
+    bdb_fingerprint_rtstats_clear();
     sqlite3_finalize(stmt);
 
     if (rc == SQLITE_DONE) {
@@ -2240,6 +2243,7 @@ out:if (rc) {
         sql_check_errors(sp->clnt, sqldb, stmt, &errstr);
         luabb_error(lua, sp, errstr);
     }
+    bdb_fingerprint_rtstats_clear();
     sqlite3_finalize(stmt);
     lua_pushinteger(lua, rc);
     return 1;
@@ -2295,6 +2299,7 @@ static int dbtable_copyfrom(Lua lua)
     }
     lua_end_step(sp->clnt, sp, stmt);
 
+    bdb_fingerprint_rtstats_clear();
     sqlite3_finalize(stmt);
 
     lua_pushinteger(lua, 0); /* Success return code. */
@@ -2878,6 +2883,7 @@ static void drop_temp_tables(SP sp)
         do {
             rc = sqlite3_step(stmt);
         } while (rc == SQLITE_ROW);
+        bdb_fingerprint_rtstats_clear();
         sqlite3_finalize(stmt);
         if (rc != SQLITE_DONE) {
             expire = 1;
@@ -3510,8 +3516,10 @@ int db_csvcopy(Lua lua)
 done:
     if (csv.z)
         free(csv.z);
-    if (stmt)
+    if (stmt) {
+        bdb_fingerprint_rtstats_clear();
         sqlite3_finalize(stmt);
+    }
     if (fp)
         fclose(fp);
     if (rc == 0)
@@ -6481,6 +6489,7 @@ static void clone_temp_tables(SP sp)
         sqlite3_stmt *stmt;
         lua_prepare_sql_with_temp_ddl(sp, strbuf_buf(sql), &stmt);
         clone_temp_table(stmt, &tmp->tbl);
+        bdb_fingerprint_rtstats_clear();
         sqlite3_finalize(stmt);
         sp->clnt->skip_peer_chk = 0;
         strbuf_free(sql);