SERVER-22078 Remove term list limits for text index in FCV 4.2

3 files changed, 119 insertions, 13 deletions

diff --git a/jstests/core/text_index_limits.js b/jstests/core/text_index_limits.js
new file mode 100644
index 00000000000..4779c58b939
--- /dev/null
+++ b/jstests/core/text_index_limits.js
@@ -0,0 +1,42 @@
+// There is no limit for the total size or the number of unique terms for text index.
+(function() {
+    "use strict";
+
+    var t = db.text_index_limits;
+    t.drop();
+
+    assert.commandWorked(t.createIndex({comments: "text"}));
+
+    // 1. Test number of unique terms exceeds 400,000
+    let commentsWithALotOfUniqueWords = "";
+    // 26^4 = 456,976 > 400,000
+    for (let ch1 = 97; ch1 < 123; ch1++) {
+        for (let ch2 = 97; ch2 < 123; ch2++) {
+            for (let ch3 = 97; ch3 < 123; ch3++) {
+                for (let ch4 = 97; ch4 < 123; ch4++) {
+                    let word = String.fromCharCode(ch1, ch2, ch3, ch4);
+                    commentsWithALotOfUniqueWords += word + " ";
+                }
+            }
+        }
+    }
+    assert.commandWorked(db.runCommand(
+        {insert: t.getName(), documents: [{_id: 1, comments: commentsWithALotOfUniqueWords}]}));
+
+    // 2. Test total size of index keys for unique terms exceeds 4MB
+
+    // 26^3 = 17576 < 400,000
+    let prefix = "a".repeat(400);
+    let commentsWithWordsOfLargeSize = "";
+    for (let ch1 = 97; ch1 < 123; ch1++) {
+        for (let ch2 = 97; ch2 < 123; ch2++) {
+            for (let ch3 = 97; ch3 < 123; ch3++) {
+                let word = String.fromCharCode(ch1, ch2, ch3);
+                commentsWithWordsOfLargeSize += prefix + word + " ";
+            }
+        }
+    }
+    assert.commandWorked(db.runCommand(
+        {insert: t.getName(), documents: [{_id: 2, comments: commentsWithWordsOfLargeSize}]}));
+
+}());
diff --git a/jstests/multiVersion/text_index_limits.js b/jstests/multiVersion/text_index_limits.js
new file mode 100644
index 00000000000..5860d5b0726
--- /dev/null
+++ b/jstests/multiVersion/text_index_limits.js
@@ -0,0 +1,53 @@
+// TODO SERVER-36440: Remove this test
+(function() {
+    "use strict";
+
+    load("jstests/libs/feature_compatibility_version.js");
+
+    // Start the node with FCV 4.0
+    let conn = MongoRunner.runMongod({binVersion: "latest"});
+    assert.commandWorked(conn.adminCommand({setFeatureCompatibilityVersion: "4.0"}));
+    var db = conn.getDB('test');
+    var t = db.text_index_limits;
+    t.drop();
+
+    assert.commandWorked(t.createIndex({comments: "text"}));
+
+    // 1. Test number of unique terms exceeds 400,000
+    let commentsWithALotOfUniqueWords = "";
+    // 26^4 = 456,976 > 400,000
+    for (let ch1 = 97; ch1 < 123; ch1++) {
+        for (let ch2 = 97; ch2 < 123; ch2++) {
+            for (let ch3 = 97; ch3 < 123; ch3++) {
+                for (let ch4 = 97; ch4 < 123; ch4++) {
+                    let word = String.fromCharCode(ch1, ch2, ch3, ch4);
+                    commentsWithALotOfUniqueWords += word + " ";
+                }
+            }
+        }
+    }
+    assert.commandFailedWithCode(
+        db.runCommand(
+            {insert: t.getName(), documents: [{_id: 1, comments: commentsWithALotOfUniqueWords}]}),
+        16732);
+
+    // 2. Test total size of index keys for unique terms exceeds 4MB
+
+    // 26^3 = 17576 < 400,000
+    let prefix = "a".repeat(400);
+    let commentsWithWordsOfLargeSize = "";
+    for (let ch1 = 97; ch1 < 123; ch1++) {
+        for (let ch2 = 97; ch2 < 123; ch2++) {
+            for (let ch3 = 97; ch3 < 123; ch3++) {
+                let word = String.fromCharCode(ch1, ch2, ch3);
+                commentsWithWordsOfLargeSize += prefix + word + " ";
+            }
+        }
+    }
+    assert.commandFailedWithCode(
+        db.runCommand(
+            {insert: t.getName(), documents: [{_id: 2, comments: commentsWithWordsOfLargeSize}]}),
+        16733);
+
+    MongoRunner.stopMongod(conn);
+}());
diff --git a/src/mongo/db/fts/fts_index_format.cpp b/src/mongo/db/fts/fts_index_format.cpp
index 770930e90c1..2b0477a5d31 100644
--- a/src/mongo/db/fts/fts_index_format.cpp
+++ b/src/mongo/db/fts/fts_index_format.cpp
@@ -36,6 +36,7 @@
 #include "mongo/db/bson/dotted_path_support.h"
 #include "mongo/db/fts/fts_index_format.h"
 #include "mongo/db/fts/fts_spec.h"
+#include "mongo/db/server_options.h"
 #include "mongo/util/hex.h"
 #include "mongo/util/md5.hpp"
 #include "mongo/util/mongoutils/str.h"
@@ -160,12 +161,17 @@ void FTSIndexFormat::getKeys(const FTSSpec& spec, const BSONObj& obj, BSONObjSet
     // create index keys from raw scores
     // only 1 per string
 
-    uassert(16732,
-            mongoutils::str::stream() << "too many unique keys for a single document to"
-                                      << " have a text index, max is "
-                                      << term_freqs.size()
-                                      << obj["_id"],
-            term_freqs.size() <= 400000);
+    // TODO SERVER-36440: Completely remove this limit in 4.3.
+    if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+        serverGlobalParams.featureCompatibility.getVersion() ==
+            ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo40) {
+        uassert(16732,
+                mongoutils::str::stream() << "too many unique keys for a single document to"
+                                          << " have a text index, max is "
+                                          << term_freqs.size()
+                                          << obj["_id"],
+                term_freqs.size() <= 400000);
+    }
 
     long long keyBSONSize = 0;
     const int MaxKeyBSONSizeMB = 4;
@@ -194,13 +200,18 @@ void FTSIndexFormat::getKeys(const FTSSpec& spec, const BSONObj& obj, BSONObjSet
         keys->insert(res);
         keyBSONSize += res.objsize();
 
-        uassert(16733,
-                mongoutils::str::stream()
-                    << "trying to index text where term list is too big, max is "
-                    << MaxKeyBSONSizeMB
-                    << "mb "
-                    << obj["_id"],
-                keyBSONSize <= (MaxKeyBSONSizeMB * 1024 * 1024));
+        // TODO SERVER-36440: Completely remove this limit in 4.3.
+        if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+            serverGlobalParams.featureCompatibility.getVersion() ==
+                ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo40) {
+            uassert(16733,
+                    mongoutils::str::stream()
+                        << "trying to index text where term list is too big, max is "
+                        << MaxKeyBSONSizeMB
+                        << "mb "
+                        << obj["_id"],
+                    keyBSONSize <= (MaxKeyBSONSizeMB * 1024 * 1024));
+        }
     }
 }