Restructure libpq code to remove some duplicity

There was some duplicate code to run SHOW transaction_read_only to
determine whether the server is read-write or read-only.  Reduce it by
adding another state to the state machine.

Author: Hari Babu Kommi
Reviewed-by: Takayuki Tsunakawa, Álvaro Herrera
Discussion: https://postgr.es/m/CAJrrPGe_qgdbbN+yBgEVpd+YLHXXjTruzk6RmTMhqrFig+32ag@mail.gmail.com

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index f03d43376c5961fcd2224606aed7eb042c30ef47..8ba0159313cb826507e42552b6c3dcb42b454e7d 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -170,7 +170,7 @@ typedef struct _internalPQconninfoOption
        char       *keyword;            /* The keyword of the option                    */
        char       *envvar;                     /* Fallback environment variable name   */
        char       *compiled;           /* Fallback compiled in default value   */
-       char       *val;                        /* Option's current value, or NULL               */
+       char       *val;                        /* Option's current value, or NULL              */
        char       *label;                      /* Label for field in connect dialog    */
        char       *dispchar;           /* Indicates how to display this field in a
                                                                 * connect dialog. Values are: "" Display
@@ -3434,6 +3434,13 @@ keep_going:                                              /* We will come back to here until there is
                                        return PGRES_POLLING_WRITING;
                                }
 
+                               /* Almost there now ... */
+                               conn->status = CONNECTION_CHECK_TARGET;
+                               goto keep_going;
+                       }
+
+               case CONNECTION_CHECK_TARGET:
+                       {
                                /*
                                 * If a read-write connection is required, see if we have one.
                                 *
@@ -3476,66 +3483,36 @@ keep_going:                                             /* We will come back to here until there is
                        }
 
                case CONNECTION_SETENV:
-
-                       /*
-                        * Do post-connection housekeeping (only needed in protocol 2.0).
-                        *
-                        * We pretend that the connection is OK for the duration of these
-                        * queries.
-                        */
-                       conn->status = CONNECTION_OK;
-
-                       switch (pqSetenvPoll(conn))
                        {
-                               case PGRES_POLLING_OK:  /* Success */
-                                       break;
-
-                               case PGRES_POLLING_READING: /* Still going */
-                                       conn->status = CONNECTION_SETENV;
-                                       return PGRES_POLLING_READING;
+                               /*
+                                * Do post-connection housekeeping (only needed in protocol 2.0).
+                                *
+                                * We pretend that the connection is OK for the duration of these
+                                * queries.
+                                */
+                               conn->status = CONNECTION_OK;
 
-                               case PGRES_POLLING_WRITING: /* Still going */
-                                       conn->status = CONNECTION_SETENV;
-                                       return PGRES_POLLING_WRITING;
+                               switch (pqSetenvPoll(conn))
+                               {
+                                       case PGRES_POLLING_OK:  /* Success */
+                                               break;
 
-                               default:
-                                       goto error_return;
-                       }
+                                       case PGRES_POLLING_READING: /* Still going */
+                                               conn->status = CONNECTION_SETENV;
+                                               return PGRES_POLLING_READING;
 
-                       /*
-                        * If a read-write connection is required, see if we have one.
-                        * (This should match the stanza in the CONNECTION_AUTH_OK case
-                        * above.)
-                        *
-                        * Servers before 7.4 lack the transaction_read_only GUC, but by
-                        * the same token they don't have any read-only mode, so we may
-                        * just skip the test in that case.
-                        */
-                       if (conn->sversion >= 70400 &&
-                               conn->target_session_attrs != NULL &&
-                               strcmp(conn->target_session_attrs, "read-write") == 0)
-                       {
-                               if (!saveErrorMessage(conn, &savedMessage))
-                                       goto error_return;
+                                       case PGRES_POLLING_WRITING: /* Still going */
+                                               conn->status = CONNECTION_SETENV;
+                                               return PGRES_POLLING_WRITING;
 
-                               conn->status = CONNECTION_OK;
-                               if (!PQsendQuery(conn,
-                                                                "SHOW transaction_read_only"))
-                               {
-                                       restoreErrorMessage(conn, &savedMessage);
-                                       goto error_return;
+                                       default:
+                                               goto error_return;
                                }
-                               conn->status = CONNECTION_CHECK_WRITABLE;
-                               restoreErrorMessage(conn, &savedMessage);
-                               return PGRES_POLLING_READING;
-                       }
-
-                       /* We can release the address list now. */
-                       release_conn_addrinfo(conn);
 
-                       /* We are open for business! */
-                       conn->status = CONNECTION_OK;
-                       return PGRES_POLLING_OK;
+                               /* Almost there now ... */
+                               conn->status = CONNECTION_CHECK_TARGET;
+                               goto keep_going;
+                       }
 
                case CONNECTION_CONSUME:
                        {

diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index 22c4954f2b71535c29721422348d6c3028723c92..5f65db30e4f3de723c86d37053ce308c43ab20b8 100644 (file)
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -67,7 +67,8 @@ typedef enum
                                                                 * connection. */
        CONNECTION_CONSUME,                     /* Wait for any pending message and consume
                                                                 * them. */
-       CONNECTION_GSS_STARTUP          /* Negotiating GSSAPI. */
+       CONNECTION_GSS_STARTUP,         /* Negotiating GSSAPI. */
+       CONNECTION_CHECK_TARGET         /* Check if we have a proper target connection */
 } ConnStatusType;
 
 typedef enum