Require ZSTD 1.1.3+ to use dictionary trainer (#4295)

Summary:
ZSTD's dynamic library exports `ZDICT_trainFromBuffer` symbol since v1.1.3, and its static library exports it since v0.6.1. We don't know whether linkage is static or dynamic, so just require v1.1.3 to use dictionary trainer.

Fixes the issue reported here: https://jira.mariadb.org/browse/MDEV-16525.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4295

Differential Revision: D9417183

Pulled By: ajkr

fbshipit-source-id: 0e89d2f48d9e7f6eee73e7f4572660a9f7122db8

HISTORY.md

@@ -8,6 +8,7 @@
 ### Public API Change
 * The merge operands are passed to `MergeOperator::ShouldMerge` in the reversed order relative to how they were merged (passed to FullMerge or FullMergeV2) for performance reasons 
 * GetAllKeyVersions() to take an extra argument of `max_num_ikeys`.
+* Using ZSTD dictionary trainer (i.e., setting `CompressionOptions::zstd_max_train_bytes` to a nonzero value) now requires ZSTD version 1.1.3 or later.
 
 ### New Features
 * Changes the format of index blocks by delta encoding the index values, which are the block handles. This saves the encoding of BlockHandle::offset of the non-head index entries in each restart interval. The feature is backward compatible but not forward compatible. It is disabled by default unless format_version 4 or above is used.

util/compression.h

@@ -36,9 +36,9 @@
 
 #if defined(ZSTD)
 #include <zstd.h>
-#if ZSTD_VERSION_NUMBER >= 800  // v0.8.0+
+#if ZSTD_VERSION_NUMBER >= 10103  // v1.1.3+
 #include <zdict.h>
-#endif  // ZSTD_VERSION_NUMBER >= 800
+#endif  // ZSTD_VERSION_NUMBER >= 10103
 namespace rocksdb {
 // Need this for the context allocation override
 // On windows we need to do this explicitly
@@ -1065,9 +1065,10 @@ inline char* ZSTD_Uncompress(const UncompressionContext& ctx,
 inline std::string ZSTD_TrainDictionary(const std::string& samples,
                                         const std::vector<size_t>& sample_lens,
                                         size_t max_dict_bytes) {
-  // Dictionary trainer is available since v0.6.1, but ZSTD was marked stable
+  // Dictionary trainer is available since v0.6.1 for static linking, but not
-  // only since v0.8.0. For now we enable the feature in stable versions only.
+  // available for dynamic linking until v1.1.3. For now we enable the feature
-#if ZSTD_VERSION_NUMBER >= 800  // v0.8.0+
+  // in v1.1.3+ only.
+#if ZSTD_VERSION_NUMBER >= 10103  // v1.1.3+
   std::string dict_data(max_dict_bytes, '\0');
   size_t dict_len = ZDICT_trainFromBuffer(
       &dict_data[0], max_dict_bytes, &samples[0], &sample_lens[0],
@@ -1078,13 +1079,13 @@ inline std::string ZSTD_TrainDictionary(const std::string& samples,
   assert(dict_len <= max_dict_bytes);
   dict_data.resize(dict_len);
   return dict_data;
-#else   // up to v0.7.x
+#else   // up to v1.1.2
   assert(false);
   (void)samples;
   (void)sample_lens;
   (void)max_dict_bytes;
   return "";
-#endif  // ZSTD_VERSION_NUMBER >= 800
+#endif  // ZSTD_VERSION_NUMBER >= 10103
 }
 
 inline std::string ZSTD_TrainDictionary(const std::string& samples,
@@ -1092,18 +1093,18 @@ inline std::string ZSTD_TrainDictionary(const std::string& samples,
                                         size_t max_dict_bytes) {
   // Dictionary trainer is available since v0.6.1, but ZSTD was marked stable
   // only since v0.8.0. For now we enable the feature in stable versions only.
-#if ZSTD_VERSION_NUMBER >= 800  // v0.8.0+
+#if ZSTD_VERSION_NUMBER >= 10103  // v1.1.3+
   // skips potential partial sample at the end of "samples"
   size_t num_samples = samples.size() >> sample_len_shift;
   std::vector<size_t> sample_lens(num_samples, size_t(1) << sample_len_shift);
   return ZSTD_TrainDictionary(samples, sample_lens, max_dict_bytes);
-#else   // up to v0.7.x
+#else   // up to v1.1.2
   assert(false);
   (void)samples;
   (void)sample_len_shift;
   (void)max_dict_bytes;
   return "";
-#endif  // ZSTD_VERSION_NUMBER >= 800
+#endif  // ZSTD_VERSION_NUMBER >= 10103
 }
 
 }  // namespace rocksdb