Speed up printing of INSERT statements in pg_dump.

In --inserts and especially --column-inserts mode, we can get a useful
speedup by generating the common prefix of all a table's INSERT commands
just once, and then printing the prebuilt string for each row.  This avoids
multiple invocations of fmtId() and other minor fooling around.

David Rowley

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 769058d78b938736b04a0fa0c45c127b8926bed9..6c16b3ca49e6ad364117bf4d47c554476cd94cb5 100644 (file)
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -1550,6 +1550,7 @@ dumpTableData_insert(Archive *fout, void *dcontext)
        TableInfo  *tbinfo = tdinfo->tdtable;
        const char *classname = tbinfo->dobj.name;
        PQExpBuffer q = createPQExpBuffer();
+       PQExpBuffer insertStmt = NULL;
        PGresult   *res;
        int                     tuple;
        int                     nfields;
@@ -1591,34 +1592,57 @@ dumpTableData_insert(Archive *fout, void *dcontext)
                nfields = PQnfields(res);
                for (tuple = 0; tuple < PQntuples(res); tuple++)
                {
-                       archprintf(fout, "INSERT INTO %s ", fmtId(classname));
-                       if (nfields == 0)
+                       /*
+                        * First time through, we build as much of the INSERT statement as
+                        * possible in "insertStmt", which we can then just print for each
+                        * line. If the table happens to have zero columns then this will
+                        * be a complete statement, otherwise it will end in "VALUES(" and
+                        * be ready to have the row's column values appended.
+                        */
+                       if (insertStmt == NULL)
                        {
+                               insertStmt = createPQExpBuffer();
+                               appendPQExpBuffer(insertStmt, "INSERT INTO %s ",
+                                                                 fmtId(classname));
+
                                /* corner case for zero-column table */
-                               archprintf(fout, "DEFAULT VALUES;\n");
-                               continue;
-                       }
-                       if (column_inserts)
-                       {
-                               resetPQExpBuffer(q);
-                               appendPQExpBuffer(q, "(");
-                               for (field = 0; field < nfields; field++)
+                               if (nfields == 0)
                                {
-                                       if (field > 0)
-                                               appendPQExpBuffer(q, ", ");
-                                       appendPQExpBufferStr(q, fmtId(PQfname(res, field)));
+                                       appendPQExpBufferStr(insertStmt, "DEFAULT VALUES;\n");
+                               }
+                               else
+                               {
+                                       /* append the list of column names if required */
+                                       if (column_inserts)
+                                       {
+                                               appendPQExpBufferStr(insertStmt, "(");
+                                               for (field = 0; field < nfields; field++)
+                                               {
+                                                       if (field > 0)
+                                                               appendPQExpBufferStr(insertStmt, ", ");
+                                                       appendPQExpBufferStr(insertStmt,
+                                                                                                fmtId(PQfname(res, field)));
+                                               }
+                                               appendPQExpBufferStr(insertStmt, ") ");
+                                       }
+
+                                       appendPQExpBufferStr(insertStmt, "VALUES (");
                                }
-                               appendPQExpBuffer(q, ") ");
-                               archputs(q->data, fout);
                        }
-                       archprintf(fout, "VALUES (");
+
+                       archputs(insertStmt->data, fout);
+
+                       /* if it is zero-column table then we're done */
+                       if (nfields == 0)
+                               continue;
+
                        for (field = 0; field < nfields; field++)
                        {
                                if (field > 0)
-                                       archprintf(fout, ", ");
+                                       archputs(", ", fout);
                                if (PQgetisnull(res, tuple, field))
                                {
-                                       archprintf(fout, "NULL");
+                                       archputs("NULL", fout);
                                        continue;
                                }
 
@@ -1647,7 +1671,7 @@ dumpTableData_insert(Archive *fout, void *dcontext)
                                                        const char *s = PQgetvalue(res, tuple, field);
 
                                                        if (strspn(s, "0123456789 +-eE.") == strlen(s))
-                                                               archprintf(fout, "%s", s);
+                                                               archputs(s, fout);
                                                        else
                                                                archprintf(fout, "'%s'", s);
                                                }
@@ -1661,9 +1685,9 @@ dumpTableData_insert(Archive *fout, void *dcontext)
 
                                        case BOOLOID:
                                                if (strcmp(PQgetvalue(res, tuple, field), "t") == 0)
-                                                       archprintf(fout, "true");
+                                                       archputs("true", fout);
                                                else
-                                                       archprintf(fout, "false");
+                                                       archputs("false", fout);
                                                break;
 
                                        default:
@@ -1676,7 +1700,7 @@ dumpTableData_insert(Archive *fout, void *dcontext)
                                                break;
                                }
                        }
-                       archprintf(fout, ");\n");
+                       archputs(");\n", fout);
                }
 
                if (PQntuples(res) <= 0)
@@ -1687,11 +1711,14 @@ dumpTableData_insert(Archive *fout, void *dcontext)
                PQclear(res);
        }
 
-       archprintf(fout, "\n\n");
+       archputs("\n\n", fout);
 
        ExecuteSqlStatement(fout, "CLOSE _pg_dump_cursor");
 
        destroyPQExpBuffer(q);
+       if (insertStmt != NULL)
+               destroyPQExpBuffer(insertStmt);
+
        return 1;
 }