libpq: Reset singlerow flag correctly in pipeline mode

When a query whose results were requested in single-row mode is the last
in the queue by the time those results are being read, the single-row
flag was not being reset, because we were returning early from
pqPipelineProcessQueue.  Move that stanza up so that the flag is always
reset at the end of sending that query's results.

Add a test for the situation.

Backpatch to 14.

Author: Denis Laxalde <denis.laxalde@dalibo.com>
Discussion: https://postgr.es/m/01af18c5-dacc-a8c8-07ee-aecc7650c3e8@dalibo.com

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index 0274c1b156c69be6bbfb5e9bb7101468327295fc..64701b562bf94d0c8f90a6bac61b8d984e28ea81 100644 (file)
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -3096,6 +3096,12 @@ pqPipelineProcessQueue(PGconn *conn)
            break;
    }
 
+   /*
+    * Reset single-row processing mode.  (Client has to set it up for each
+    * query, if desired.)
+    */
+   conn->singleRowMode = false;
+
    /*
     * If there are no further commands to process in the queue, get us in
     * "real idle" mode now.
@@ -3115,12 +3121,6 @@ pqPipelineProcessQueue(PGconn *conn)
    /* Initialize async result-accumulation state */
    pqClearAsyncResult(conn);
 
-   /*
-    * Reset single-row processing mode.  (Client has to set it up for each
-    * query, if desired.)
-    */
-   conn->singleRowMode = false;
-
    if (conn->pipelineStatus == PQ_PIPELINE_ABORTED &&
        conn->cmd_queue_head->queryclass != PGQUERY_SYNC)
    {

diff --git a/src/test/modules/libpq_pipeline/libpq_pipeline.c b/src/test/modules/libpq_pipeline/libpq_pipeline.c
index c609f42258984e175f1538165f3435c3ccdebbda..a37e4e250080b03bee44a7fcd11aec800e9865d9 100644 (file)
--- a/src/test/modules/libpq_pipeline/libpq_pipeline.c
+++ b/src/test/modules/libpq_pipeline/libpq_pipeline.c
@@ -1153,11 +1153,11 @@ test_singlerowmode(PGconn *conn)
    int         i;
    bool        pipeline_ended = false;
 
-   /* 1 pipeline, 3 queries in it */
    if (PQenterPipelineMode(conn) != 1)
        pg_fatal("failed to enter pipeline mode: %s",
                 PQerrorMessage(conn));
 
+   /* One series of three commands, using single-row mode for the first two. */
    for (i = 0; i < 3; i++)
    {
        char       *param[1];
@@ -1249,6 +1249,49 @@ test_singlerowmode(PGconn *conn)
            pg_fatal("didn't get expected terminating TUPLES_OK");
    }
 
+   /*
+    * Now issue one command, get its results in with single-row mode, then
+    * issue another command, and get its results in normal mode; make sure
+    * the single-row mode flag is reset as expected.
+    */
+   if (PQsendQueryParams(conn, "SELECT generate_series(0, 0)",
+                         0, NULL, NULL, NULL, NULL, 0) != 1)
+       pg_fatal("failed to send query: %s",
+                PQerrorMessage(conn));
+   if (PQsendFlushRequest(conn) != 1)
+       pg_fatal("failed to send flush request");
+   if (PQsetSingleRowMode(conn) != 1)
+       pg_fatal("PQsetSingleRowMode() failed");
+   res = PQgetResult(conn);
+   if (res == NULL)
+       pg_fatal("unexpected NULL");
+   if (PQresultStatus(res) != PGRES_SINGLE_TUPLE)
+       pg_fatal("Expected PGRES_SINGLE_TUPLE, got %s",
+                PQresStatus(PQresultStatus(res)));
+   res = PQgetResult(conn);
+   if (res == NULL)
+       pg_fatal("unexpected NULL");
+   if (PQresultStatus(res) != PGRES_TUPLES_OK)
+       pg_fatal("Expected PGRES_TUPLES_OK, got %s",
+                PQresStatus(PQresultStatus(res)));
+   if (PQgetResult(conn) != NULL)
+       pg_fatal("expected NULL result");
+
+   if (PQsendQueryParams(conn, "SELECT 1",
+                         0, NULL, NULL, NULL, NULL, 0) != 1)
+       pg_fatal("failed to send query: %s",
+                PQerrorMessage(conn));
+   if (PQsendFlushRequest(conn) != 1)
+       pg_fatal("failed to send flush request");
+   res = PQgetResult(conn);
+   if (res == NULL)
+       pg_fatal("unexpected NULL");
+   if (PQresultStatus(res) != PGRES_TUPLES_OK)
+       pg_fatal("Expected PGRES_TUPLES_OK, got %s",
+                PQresStatus(PQresultStatus(res)));
+   if (PQgetResult(conn) != NULL)
+       pg_fatal("expected NULL result");
+
    if (PQexitPipelineMode(conn) != 1)
        pg_fatal("failed to end pipeline mode: %s", PQerrorMessage(conn));
 

diff --git a/src/test/modules/libpq_pipeline/traces/singlerow.trace b/src/test/modules/libpq_pipeline/traces/singlerow.trace
index 9de99befcc1f54bab9ff0430151b016eb62bfe6a..83043e1407e855624a372f713ccc594eaee4cc81 100644 (file)
--- a/src/test/modules/libpq_pipeline/traces/singlerow.trace
+++ b/src/test/modules/libpq_pipeline/traces/singlerow.trace
@@ -36,4 +36,24 @@ B    12  DataRow  1 2 '45'
 B  12  DataRow  1 2 '46'
 B  13  CommandComplete  "SELECT 5"
 B  5   ReadyForQuery    I
+F  36  Parse    "" "SELECT generate_series(0, 0)" 0
+F  14  Bind     "" "" 0 0 1 0
+F  6   Describe     P ""
+F  9   Execute  "" 0
+F  4   Flush
+B  4   ParseComplete
+B  4   BindComplete
+B  40  RowDescription   1 "generate_series" NNNN 0 NNNN 4 -1 0
+B  11  DataRow  1 1 '0'
+B  13  CommandComplete  "SELECT 1"
+F  16  Parse    "" "SELECT 1" 0
+F  14  Bind     "" "" 0 0 1 0
+F  6   Describe     P ""
+F  9   Execute  "" 0
+F  4   Flush
+B  4   ParseComplete
+B  4   BindComplete
+B  33  RowDescription   1 "?column?" NNNN 0 NNNN 4 -1 0
+B  11  DataRow  1 1 '1'
+B  13  CommandComplete  "SELECT 1"
 F  4   Terminate