From 69c2cf11d3f964e2488927e3341e375e15413751 Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Tue, 12 Apr 2022 18:38:13 +0800
Subject: [PATCH] ehn(query): return the performance_schema db when "show
 databases" sql statement issued.

---
 include/util/tdef.h                 |  1 +
 source/dnode/mnode/impl/src/mndDb.c | 25 +++++++++++++++++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/include/util/tdef.h b/include/util/tdef.h
index 263c90c0f8..246c3e2eaa 100644
--- a/include/util/tdef.h
+++ b/include/util/tdef.h
@@ -95,6 +95,7 @@ extern const int32_t TYPE_BYTES[15];
 #define TSDB_TIME_PRECISION_NANO_STR  "ns"
 
 #define TSDB_INFORMATION_SCHEMA_DB            "information_schema"
+#define TSDB_PERFORMANCE_SCHEMA_DB            "performance_schema"
 #define TSDB_INS_TABLE_DNODES                 "dnodes"
 #define TSDB_INS_TABLE_MNODES                 "mnodes"
 #define TSDB_INS_TABLE_MODULES                "modules"
diff --git a/source/dnode/mnode/impl/src/mndDb.c b/source/dnode/mnode/impl/src/mndDb.c
index 49e9ccaba6..f82e381715 100644
--- a/source/dnode/mnode/impl/src/mndDb.c
+++ b/source/dnode/mnode/impl/src/mndDb.c
@@ -1486,6 +1486,18 @@ static void setInformationSchemaDbCfg(SDbObj *pDbObj) {
   pDbObj->cfg.precision = TSDB_TIME_PRECISION_MILLI;
 }
 
+static void setPerfSchemaDbCfg(SDbObj* pDbObj) {
+  ASSERT(pDbObj != NULL);
+  strncpy(pDbObj->name, TSDB_PERFORMANCE_SCHEMA_DB, tListLen(pDbObj->name));
+
+  pDbObj->createdTime = 0;
+  pDbObj->cfg.numOfVgroups = 0;
+  pDbObj->cfg.quorum = 1;
+  pDbObj->cfg.replications = 1;
+  pDbObj->cfg.update = 1;
+  pDbObj->cfg.precision = TSDB_TIME_PRECISION_MILLI;
+}
+
 static bool mndGetTablesOfDbFp(SMnode *pMnode, void *pObj, void *p1, void *p2, void *p3) {
   SVgObj  *pVgroup = pObj;
   int32_t *numOfTables = p1;
@@ -1515,10 +1527,15 @@ static int32_t mndRetrieveDbs(SNodeMsg *pReq, SShowObj *pShow, char *data, int32
   }
 
   // Append the information_schema database into the result.
-  if (numOfRows < rowsCapacity) {
-    SDbObj dummyISDb = {0};
-    setInformationSchemaDbCfg(&dummyISDb);
-    dumpDbInfoToPayload(data, &dummyISDb, pShow, numOfRows, rowsCapacity, 14);
+  if (numOfRows  + 2 < rowsCapacity) {
+    SDbObj infoschemaDb = {0};
+    setInformationSchemaDbCfg(&infoschemaDb);
+    dumpDbInfoToPayload(data, &infoschemaDb, pShow, numOfRows, rowsCapacity, 14);
+    numOfRows += 1;
+
+    SDbObj perfschemaDb = {0};
+    setPerfSchemaDbCfg(&perfschemaDb);
+    dumpDbInfoToPayload(data, &perfschemaDb, pShow, numOfRows, rowsCapacity, 14);
     numOfRows += 1;
   }
 
-- 
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