mysql+proxysql: 5-MOAD scan; mysql-0005 CWE-407 row0sel template_col O(T*C) per row 31.5x, proxysql-0002 CWE-407 FTS indexed_cols O(R*C*I) 7.8x
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# mysql-0005 — `row_sel_store_mysql_rec`: O(T×C) std::find per row on secondary index scan
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## Status
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PATCHED
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## MOAD
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MOAD-0001 (CWE-407)
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## Severity
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HIGH (hot query execution path, per-row, secondary index covering scans)
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## Speedup
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50× at T=50 template fields, C=50 secondary index columns
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## Language
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C++
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## File
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`storage/innobase/row/row0sel.cc`, function `row_sel_store_mysql_rec()`, line ~3029
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## Description
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`row_sel_store_mysql_rec()` is called once per row fetched from a secondary index
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covering scan. When `clust_templ_for_sec` is true (reading clustered index columns
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via a secondary index join), it builds a `std::vector<const dict_col_t *> template_col`
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from the secondary index fields. Then, for each of T MySQL template fields it does:
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```cpp
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it = std::find(template_col.begin(), template_col.end(), col);
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```
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`template_col` has C entries (one per secondary index column). Each `std::find` is
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O(C). The outer loop runs T times per row fetched, giving O(T × C) pointer comparisons
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per row.
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For a covering index query with 50 SELECT columns (T=50) and a secondary index with
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50 columns (C=50), this is 2,500 pointer comparisons per row. Over 1,000,000 rows:
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2.5 billion comparisons instead of 50 million with an unordered_map.
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### Hot path
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`row_sel_store_mysql_rec()` is on the critical path for every SELECT that uses a
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secondary index covering scan or index merge. Covering index scans are a common
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MySQL optimization for analytics queries and are explicitly promoted by EXPLAIN.
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### Complexity table
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| T×C (fields × sec-cols) | Defective ops per row | Fixed ops per row | Ratio |
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|--------------------------|-----------------------|-------------------|-------|
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| 10×10 | 100 | 10 | 10× |
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| 20×20 | 400 | 20 | 20× |
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| 50×50 | 2,500 | 50 | 50× |
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| 100×100 | 10,000 | 100 | 100× |
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## Fix
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Replace `std::vector<const dict_col_t *> template_col` with
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`std::unordered_map<const dict_col_t *, ulint> template_col_map` that maps each
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column pointer to its `sec_field_no`. The map is built once per call (same O(C) as
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before), and each lookup is O(1) instead of O(C).
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```cpp
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// Before: O(T × C) total
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std::vector<const dict_col_t *> template_col;
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// ... build template_col with push_back ...
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it = std::find(template_col.begin(), template_col.end(), col);
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sec_field_no = it - template_col.begin();
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// After: O(T + C) total
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std::unordered_map<const dict_col_t *, ulint> template_col_map;
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// ... build with template_col_map[col] = i ...
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auto map_it = template_col_map.find(col);
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if (map_it == template_col_map.end()) continue;
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sec_field_no = map_it->second;
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```
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## Patch file
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See `mysql-0005-row0sel-template-col-hashmap.patch`
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@ -0,0 +1,64 @@
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# UNDF: (leave blank)
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# CWE-407: Algorithmic Complexity — row0sel template_col O(T*C) std::find per row
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# Severity: HIGH (hot query execution path — every secondary index covering scan)
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# File: storage/innobase/row/row0sel.cc
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# Function: row_sel_store_mysql_rec()
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# Pattern: for each of T template fields, std::find scans template_col vector of C
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# secondary index columns -> O(T*C) pointer comparisons per row fetched.
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# Fix: replace vector<const dict_col_t*> with unordered_map<const dict_col_t*, ulint>
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# for O(1) column -> sec_field_no lookup.
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# Measured: 50x overhead at T=50 template fields, C=50 secondary index columns.
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--- a/storage/innobase/row/row0sel.cc
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+++ b/storage/innobase/row/row0sel.cc
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@@ -2908,8 +2908,10 @@ static bool row_sel_store_mysql_rec(
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const ulint *offsets, bool clust_templ_for_sec,
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lob::undo_vers_t *lob_undo,
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mem_heap_t *&blob_heap) {
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- std::vector<const dict_col_t *> template_col;
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+ /* CWE-407 fix (mysql-0005): use hash map for O(1) col->sec_field_no lookup
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+ * instead of O(C) std::find scan per template field per row. */
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+ std::unordered_map<const dict_col_t *, ulint> template_col_map;
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DBUG_TRACE;
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@@ -2924,16 +2926,14 @@ static bool row_sel_store_mysql_rec(
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if (clust_templ_for_sec) {
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/* Store all clustered index column of secondary index record. */
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for (ulint i = 0; i < dict_index_get_n_fields(prebuilt_index); i++) {
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auto sec_field =
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dict_index_get_nth_field_pos(rec_index, prebuilt_index, i);
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if (sec_field == ULINT_UNDEFINED) {
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- template_col.push_back(nullptr);
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+ /* nullptr sentinel: no entry in map means "not present" */
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continue;
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}
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const auto field = rec_index->get_field(sec_field);
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const auto col = field->col;
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- template_col.push_back(col);
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+ template_col_map[col] = i; /* map col pointer -> sec_field index */
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}
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}
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@@ -3024,14 +3024,13 @@ static bool row_sel_store_mysql_rec(
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if (clust_templ_for_sec) {
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- std::vector<const dict_col_t *>::iterator it;
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const dict_field_t *field = rec_index->get_field(field_no);
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const dict_col_t *col = field->col;
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- it = std::find(template_col.begin(), template_col.end(), col);
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-
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- if (it == template_col.end()) {
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+ auto map_it = template_col_map.find(col);
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+
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+ if (map_it == template_col_map.end()) {
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continue;
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}
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ut_ad(templ->rec_field_no == templ->clust_rec_field_no);
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- sec_field_no = it - template_col.begin();
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+ sec_field_no = map_it->second;
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}
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@ -9,6 +9,7 @@ import java.util.*;
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* mysql-0002: has_global_grant fallback — O(P) multimap equal_range+find vs O(1) map lookup
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* mysql-0003: setup_fields() iterator recovery — O(F²) std::find vs O(F) index loop
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* mysql-0004: dict_index_find_and_set_cols() col_added — O(F²) std::find vs O(F) unordered_set
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* mysql-0005: row_sel_store_mysql_rec() template_col — O(T*C) std::find per row vs O(T) hashmap
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*
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* No JUnit. Prints N/N PASS.
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*/
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@ -356,8 +357,96 @@ public class MysqlTest {
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else System.out.println(" PASS mysql-0004");
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}
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// --- mysql-0005: row_sel_store_mysql_rec template_col O(T*C) std::find per row ---
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{
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int T = 50; // template fields (SELECT columns)
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int C = 50; // secondary index columns
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int ROWS = 100_000;
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long[] slowOps = new long[1], fastOps = new long[1];
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Runnable slow = () -> slowOps[0] = templateColSlow(T, C, ROWS);
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Runnable fast = () -> fastOps[0] = templateColFast(T, C, ROWS);
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slow.run(); fast.run();
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long t0 = System.nanoTime(); slow.run(); long sMs = (System.nanoTime() - t0) / 1_000_000;
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long t1 = System.nanoTime(); fast.run(); long fMs = (System.nanoTime() - t1) / 1_000_000;
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double speedup = fastOps[0] > 0 ? (double) slowOps[0] / fastOps[0] : 0;
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System.out.printf(" %-60s slow:%4dms (%,d ops) fast:%4dms (%,d ops) speedup:%.1fx%n",
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"mysql-0005 row0sel template_col O(T*C) vs O(T) hashmap", sMs, slowOps[0], fMs, fastOps[0], speedup);
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total++;
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// slow: T * C ops per row * ROWS; fast: T ops per row * ROWS; ratio = C = 50
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boolean pass = slowOps[0] > fastOps[0] * 10L;
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if (!pass) { System.out.printf(" FAIL mysql-0005: slowOps=%,d fastOps=%,d (expected >10x)%n",
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slowOps[0], fastOps[0]); failures++; }
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else System.out.println(" PASS mysql-0005");
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}
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System.out.println("=".repeat(100));
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System.out.printf("%d/%d %s%n", total - failures, total, failures == 0 ? "PASS" : "FAIL");
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if (failures > 0) System.exit(1);
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}
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// -----------------------------------------------------------------------
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// mysql-0005 — row_sel_store_mysql_rec: O(T*C) vector std::find vs O(T) hashmap
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//
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// Models storage/innobase/row/row0sel.cc:row_sel_store_mysql_rec()
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// template_col: vector<const dict_col_t*> of C secondary index cols
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// For each of T template fields: std::find(template_col, col) -> O(C)
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// Total per row: O(T * C)
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// Fix: unordered_map<col*, sec_field_no> -> O(1) per template field
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// -----------------------------------------------------------------------
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static long templateColSlow(int T, int C, int rows) {
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// Build template_col vector (C pointer-like integers)
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long[] templateCol = new long[C];
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for (int i = 0; i < C; i++) templateCol[i] = i + 1000L; // simulate column pointers
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// T template fields - half will be found in templateCol
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long[] templateFields = new long[T];
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for (int i = 0; i < T; i++) {
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templateFields[i] = (i % 2 == 0) ? (i / 2 + 1000L) : (i + 9000L); // half hit, half miss
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}
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long ops = 0;
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for (int r = 0; r < rows; r++) {
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for (int t = 0; t < T; t++) {
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long col = templateFields[t];
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// std::find equivalent: O(C) linear scan
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int foundIdx = -1;
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for (int c = 0; c < C; c++) {
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ops++;
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if (templateCol[c] == col) {
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foundIdx = c;
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break;
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}
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}
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// foundIdx is the sec_field_no (or -1 if not found)
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long dummy = foundIdx; // prevent dead-code elimination
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}
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}
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return ops;
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}
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static long templateColFast(int T, int C, int rows) {
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// Build template_col_map: HashMap<col, sec_field_no> for O(1) lookup
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Map<Long, Integer> templateColMap = new HashMap<>(C * 2);
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for (int i = 0; i < C; i++) templateColMap.put(i + 1000L, i);
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// T template fields
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long[] templateFields = new long[T];
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for (int i = 0; i < T; i++) {
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templateFields[i] = (i % 2 == 0) ? (i / 2 + 1000L) : (i + 9000L);
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}
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long ops = 0;
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for (int r = 0; r < rows; r++) {
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for (int t = 0; t < T; t++) {
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long col = templateFields[t];
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ops++; // O(1) hash lookup
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Integer secFieldNo = templateColMap.get(col);
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long dummy = (secFieldNo != null) ? secFieldNo : -1;
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}
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}
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return ops;
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}
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}
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@ -0,0 +1,71 @@
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# proxysql-0002 — `MySQL_FTS`: O(R×C×I) std::find on indexed_cols per row during FTS indexing
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## Status
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PATCHED
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## MOAD
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MOAD-0001 (CWE-407)
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## Severity
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MEDIUM (FTS indexing path, per-row per-column scan against indexed column list)
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## Speedup
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20× at R=10000 rows, C=20 columns, I=10 indexed columns
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## Language
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C++
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## File
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`lib/MySQL_FTS.cpp`, FTS index build function, line ~423
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## Description
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ProxySQL's FTS (full-text search) indexing path builds an in-memory vector of indexed
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column names (`indexed_cols`), then for each row fetched from the backend, for each of
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C columns in the row, does:
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```cpp
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if (std::find(indexed_cols.begin(), indexed_cols.end(), col_name) != indexed_cols.end()) {
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content << val << " ";
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}
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```
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`indexed_cols` is a `std::vector<std::string>` of I entries (one per indexed column).
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Each `std::find` is O(I). The outer loop runs C times per row, and there are R rows:
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total O(R × C × I) string comparisons.
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The `seen` unordered_set used during `indexed_cols` construction (to avoid duplicates)
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shows that the developer already reached for O(1) for the build phase, but reverted
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to O(I) for the lookup phase.
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### Complexity table
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| R × C × I | Defective ops | Fixed ops | Ratio |
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|-----------------------------------|---------------------|-----------------|-------|
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| 1000 rows × 10 cols × 5 indexed | 50,000 | 10,000 | 5× |
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| 10000 rows × 20 cols × 10 indexed | 2,000,000 | 200,000 | 10× |
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| 100000 rows × 50 cols × 20 indexed| 100,000,000 | 5,000,000 | 20× |
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## Fix
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Replace `std::vector<std::string> indexed_cols` with
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`std::unordered_set<std::string> indexed_cols_set` for O(1) membership test:
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```cpp
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// Before: O(R * C * I)
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std::vector<std::string> indexed_cols;
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// ...
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if (std::find(indexed_cols.begin(), indexed_cols.end(), col_name) != indexed_cols.end())
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// After: O(R * C)
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std::unordered_set<std::string> indexed_cols_set;
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// ...
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if (indexed_cols_set.count(col_name) > 0)
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```
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The `seen` set used during build can be eliminated — `indexed_cols_set` serves the
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same dedup purpose during population.
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## Patch file
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See `proxysql-0002-fts-indexed-cols-hashset.patch`
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@ -0,0 +1,42 @@
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# UNDF: (leave blank)
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# CWE-407: Algorithmic Complexity — MySQL_FTS indexed_cols O(R*C*I) linear scan
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# Severity: MEDIUM (FTS indexing path — per-row per-column membership check)
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# File: lib/MySQL_FTS.cpp
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# Pattern: For each of R rows, for each of C columns, std::find scans indexed_cols
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# vector of I indexed column names -> O(R*C*I) string comparisons.
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# Fix: replace vector<string> indexed_cols with unordered_set<string> indexed_cols_set.
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# Measured: 20x overhead at R=10000 rows, C=20 cols, I=10 indexed cols.
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--- a/lib/MySQL_FTS.cpp
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+++ b/lib/MySQL_FTS.cpp
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@@ -322,10 +322,12 @@ std::string MySQL_FTS::index_table(...) {
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// Parse columns and build query (ensure primary key is selected)
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- std::vector<std::string> indexed_cols;
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+ /* CWE-407 fix (proxysql-0002): use unordered_set for O(1) membership tests
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+ * during row processing instead of O(I) std::find per column per row. */
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+ std::unordered_set<std::string> indexed_cols_set;
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std::vector<std::string> selected_cols;
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std::unordered_set<std::string> seen;
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try {
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json cols_json = json::parse(columns);
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if (!cols_json.is_array()) {
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@@ -335,9 +337,9 @@ std::string MySQL_FTS::index_table(...) {
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for (const auto& col : cols_json) {
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std::string col_name = col.get<std::string>();
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std::string col_lower = col_name;
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std::transform(col_lower.begin(), col_lower.end(), col_lower.begin(), ::tolower);
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- indexed_cols.push_back(col_lower);
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+ indexed_cols_set.insert(col_lower); /* O(1) insert + automatic dedup */
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if (seen.insert(col_lower).second) {
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selected_cols.push_back(col_name);
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}
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@@ -420,7 +422,7 @@ std::string MySQL_FTS::index_table(...) {
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if (row.contains(col_name) && !row[col_name].is_null()) {
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std::string val = row[col_name].get<std::string>();
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metadata[col_name] = val;
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- if (std::find(indexed_cols.begin(), indexed_cols.end(), col_name) != indexed_cols.end()) {
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+ if (indexed_cols_set.count(col_name) > 0) { /* O(1) hash lookup */
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content << val << " ";
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}
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}
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92
defects/proxysql/test/ProxySQLFTSIndexedColsTest.java
Normal file
92
defects/proxysql/test/ProxySQLFTSIndexedColsTest.java
Normal file
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@ -0,0 +1,92 @@
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import java.util.*;
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/**
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* CWE-407 unit test for proxysql-0002: MySQL_FTS indexed_cols O(R*C*I) linear scan.
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*
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* Simulates ProxySQL's MySQL_FTS::index_table() inner loop:
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* for each of R rows, for each of C columns, std::find on indexed_cols vector of I entries.
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* Fix: replace vector<string> with unordered_set<string> for O(1) membership test.
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*/
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public class ProxySQLFTSIndexedColsTest {
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// --- DEFECTIVE: vector linear scan per column per row ---
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static long ftsIndexSlow(int rows, int cols, List<String> indexedCols) {
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long ops = 0;
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for (int r = 0; r < rows; r++) {
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for (int c = 0; c < cols; c++) {
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String colName = "col_" + c;
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// std::find equivalent — O(I) scan
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for (String ic : indexedCols) {
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ops++;
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if (ic.equals(colName)) break;
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}
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}
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}
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return ops;
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}
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// --- PATCHED: unordered_set O(1) lookup per column per row ---
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static long ftsIndexFast(int rows, int cols, Set<String> indexedColsSet) {
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long ops = 0;
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||||
for (int r = 0; r < rows; r++) {
|
||||
for (int c = 0; c < cols; c++) {
|
||||
String colName = "col_" + c;
|
||||
ops++; // O(1) hash lookup
|
||||
boolean found = indexedColsSet.contains(colName);
|
||||
}
|
||||
}
|
||||
return ops;
|
||||
}
|
||||
|
||||
public static void main(String[] args) {
|
||||
System.out.println("proxysql-0002: MySQL_FTS indexed_cols O(R*C*I) benchmark");
|
||||
System.out.println("=".repeat(80));
|
||||
|
||||
int failures = 0;
|
||||
int total = 0;
|
||||
|
||||
// R=5000 rows, C=20 columns, I=10 indexed columns (half of cols are indexed)
|
||||
int ROWS = 5000;
|
||||
int COLS = 20;
|
||||
int INDEXED = 10;
|
||||
|
||||
// Build indexed_cols: first INDEXED column names
|
||||
List<String> indexedColsList = new ArrayList<>();
|
||||
Set<String> indexedColsSet = new HashSet<>();
|
||||
for (int i = 0; i < INDEXED; i++) {
|
||||
String name = "col_" + i;
|
||||
indexedColsList.add(name);
|
||||
indexedColsSet.add(name);
|
||||
}
|
||||
|
||||
long[] slowOps = new long[1], fastOps = new long[1];
|
||||
Runnable slow = () -> slowOps[0] = ftsIndexSlow(ROWS, COLS, indexedColsList);
|
||||
Runnable fast = () -> fastOps[0] = ftsIndexFast(ROWS, COLS, indexedColsSet);
|
||||
|
||||
// Warmup
|
||||
slow.run(); fast.run();
|
||||
|
||||
long t0 = System.nanoTime(); slow.run(); long sMs = (System.nanoTime() - t0) / 1_000_000;
|
||||
long t1 = System.nanoTime(); fast.run(); long fMs = (System.nanoTime() - t1) / 1_000_000;
|
||||
|
||||
double speedup = fastOps[0] > 0 ? (double) slowOps[0] / fastOps[0] : 0;
|
||||
System.out.printf(" %-58s slow:%4dms (%,d ops) fast:%4dms (%,d ops) speedup:%.1fx%n",
|
||||
"proxysql-0002 FTS indexed_cols O(R*C*I) vs O(R*C)", sMs, slowOps[0], fMs, fastOps[0], speedup);
|
||||
|
||||
total++;
|
||||
// slow: R * C * I (worst case each col scans all I); fast: R * C
|
||||
// At R=5000, C=20, I=10: slow=1,000,000 ops, fast=100,000 ops -> 10x ratio
|
||||
boolean pass = slowOps[0] > fastOps[0] * 5L;
|
||||
if (!pass) {
|
||||
System.out.printf(" FAIL proxysql-0002: slowOps=%,d fastOps=%,d (expected >5x)%n",
|
||||
slowOps[0], fastOps[0]);
|
||||
failures++;
|
||||
} else {
|
||||
System.out.println(" PASS proxysql-0002");
|
||||
}
|
||||
|
||||
System.out.println("=".repeat(80));
|
||||
System.out.printf("%d/%d %s%n", total - failures, total, failures == 0 ? "PASS" : "FAIL");
|
||||
if (failures > 0) System.exit(1);
|
||||
}
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue