Create a FETCH_COUNT parameter that causes psql to execute SELECT-like
queries via a cursor, fetching a limited number of rows at a time and therefore not risking exhausting memory. A disadvantage of the scheme is that 'aligned' output mode will align each group of rows independently leading to odd-looking output, but all the other output formats work reasonably well. Chris Mair, with some additional hacking by moi.
This commit is contained in:
Tom Lane
parent
7c5ac5ce22
commit
c2f60711d2
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.166 2006/07/27 19:52:04 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.167 2006/08/29 22:25:04 tgl Exp $
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PostgreSQL documentation
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-->
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@ -2007,6 +2007,33 @@ bar
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>FETCH_COUNT</varname></term>
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<listitem>
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<para>
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If this variable is set to an integer value > 0,
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the results of <command>SELECT</command> queries are fetched
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and displayed in groups of that many rows, rather than the
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default behavior of collecting the entire result set before
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display. Therefore only a
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limited amount of memory is used, regardless of the size of
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the result set. Settings of 100 to 1000 are commonly used
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when enabling this feature.
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Keep in mind that when using this feature, a query may
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fail after having already displayed some rows.
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</para>
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<tip>
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<para>
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Although you can use any output format with this feature,
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the default <literal>aligned</> format tends to look bad
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because each group of <varname>FETCH_COUNT</varname> rows
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will be formatted separately, leading to varying column
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widths across the row groups. The other output formats work better.
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</para>
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</tip>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>HISTCONTROL</varname></term>
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<listitem>
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@ -3,7 +3,7 @@
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*
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* Copyright (c) 2000-2006, PostgreSQL Global Development Group
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*
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* $PostgreSQL: pgsql/src/bin/psql/common.c,v 1.126 2006/08/29 15:19:50 tgl Exp $
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* $PostgreSQL: pgsql/src/bin/psql/common.c,v 1.127 2006/08/29 22:25:07 tgl Exp $
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*/
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#include "postgres_fe.h"
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#include "common.h"
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@ -28,6 +28,7 @@
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#include "command.h"
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#include "copy.h"
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#include "mb/pg_wchar.h"
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#include "mbprint.h"
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/* Workarounds for Windows */
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@ -53,7 +54,9 @@ typedef struct _timeb TimevalStruct;
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#endif
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static bool ExecQueryUsingCursor(const char *query, double *elapsed_msec);
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static bool command_no_begin(const char *query);
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static bool is_select_command(const char *query);
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/*
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* "Safe" wrapper around strdup()
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@ -450,18 +453,15 @@ ResetCancelConn(void)
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* AcceptResult
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*
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* Checks whether a result is valid, giving an error message if necessary;
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* resets cancelConn as needed, and ensures that the connection to the backend
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* is still up.
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* and ensures that the connection to the backend is still up.
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*
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* Returns true for valid result, false for error state.
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*/
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static bool
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AcceptResult(const PGresult *result, const char *query)
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AcceptResult(const PGresult *result)
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{
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bool OK = true;
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ResetCancelConn();
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if (!result)
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OK = false;
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else
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@ -560,7 +560,9 @@ PSQLexec(const char *query, bool start_xact)
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res = PQexec(pset.db, query);
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if (!AcceptResult(res, query) && res)
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ResetCancelConn();
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if (!AcceptResult(res))
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{
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PQclear(res);
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res = NULL;
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@ -602,6 +604,7 @@ PrintQueryTuples(const PGresult *results)
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/* write output to \g argument, if any */
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if (pset.gfname)
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{
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/* keep this code in sync with ExecQueryUsingCursor */
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FILE *queryFout_copy = pset.queryFout;
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bool queryFoutPipe_copy = pset.queryFoutPipe;
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@ -782,11 +785,10 @@ bool
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SendQuery(const char *query)
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{
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PGresult *results;
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TimevalStruct before,
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after;
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PGTransactionStatusType transaction_status;
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double elapsed_msec = 0;
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bool OK,
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on_error_rollback_savepoint = false;
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PGTransactionStatusType transaction_status;
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static bool on_error_rollback_warning = false;
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if (!pset.db)
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@ -869,20 +871,38 @@ SendQuery(const char *query)
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}
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}
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if (pset.timing)
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GETTIMEOFDAY(&before);
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if (pset.fetch_count <= 0 || !is_select_command(query))
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{
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/* Default fetch-it-all-and-print mode */
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TimevalStruct before,
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after;
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results = PQexec(pset.db, query);
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if (pset.timing)
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GETTIMEOFDAY(&before);
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/* these operations are included in the timing result: */
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OK = (AcceptResult(results, query) && ProcessCopyResult(results));
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results = PQexec(pset.db, query);
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if (pset.timing)
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GETTIMEOFDAY(&after);
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/* these operations are included in the timing result: */
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ResetCancelConn();
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OK = (AcceptResult(results) && ProcessCopyResult(results));
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/* but printing results isn't: */
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if (OK)
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OK = PrintQueryResults(results);
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if (pset.timing)
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{
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GETTIMEOFDAY(&after);
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elapsed_msec = DIFF_MSEC(&after, &before);
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}
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/* but printing results isn't: */
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if (OK)
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OK = PrintQueryResults(results);
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}
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else
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{
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/* Fetch-in-segments mode */
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OK = ExecQueryUsingCursor(query, &elapsed_msec);
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ResetCancelConn();
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results = NULL; /* PQclear(NULL) does nothing */
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}
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/* If we made a temporary savepoint, possibly release/rollback */
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if (on_error_rollback_savepoint)
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@ -904,9 +924,10 @@ SendQuery(const char *query)
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* the user did RELEASE or ROLLBACK, our savepoint is gone. If
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* they issued a SAVEPOINT, releasing ours would remove theirs.
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*/
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if (strcmp(PQcmdStatus(results), "SAVEPOINT") == 0 ||
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strcmp(PQcmdStatus(results), "RELEASE") == 0 ||
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strcmp(PQcmdStatus(results), "ROLLBACK") == 0)
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if (results &&
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(strcmp(PQcmdStatus(results), "SAVEPOINT") == 0 ||
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strcmp(PQcmdStatus(results), "RELEASE") == 0 ||
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strcmp(PQcmdStatus(results), "ROLLBACK") == 0))
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svptres = NULL;
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else
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svptres = PQexec(pset.db, "RELEASE pg_psql_temporary_savepoint");
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@ -927,7 +948,7 @@ SendQuery(const char *query)
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/* Possible microtiming output */
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if (OK && pset.timing)
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printf(_("Time: %.3f ms\n"), DIFF_MSEC(&after, &before));
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printf(_("Time: %.3f ms\n"), elapsed_msec);
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/* check for events that may occur during query execution */
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@ -947,6 +968,198 @@ SendQuery(const char *query)
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}
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/*
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* ExecQueryUsingCursor: run a SELECT-like query using a cursor
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*
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* This feature allows result sets larger than RAM to be dealt with.
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*
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* Returns true if the query executed successfully, false otherwise.
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*
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* If pset.timing is on, total query time (exclusive of result-printing) is
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* stored into *elapsed_msec.
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*/
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static bool
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ExecQueryUsingCursor(const char *query, double *elapsed_msec)
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{
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bool OK = true;
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PGresult *results;
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PQExpBufferData buf;
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printQueryOpt my_popt = pset.popt;
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FILE *queryFout_copy = pset.queryFout;
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bool queryFoutPipe_copy = pset.queryFoutPipe;
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bool started_txn = false;
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bool did_pager = false;
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int ntuples;
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char fetch_cmd[64];
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TimevalStruct before,
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after;
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*elapsed_msec = 0;
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/* initialize print options for partial table output */
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my_popt.topt.start_table = true;
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my_popt.topt.stop_table = false;
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my_popt.topt.prior_records = 0;
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if (pset.timing)
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GETTIMEOFDAY(&before);
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/* if we're not in a transaction, start one */
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if (PQtransactionStatus(pset.db) == PQTRANS_IDLE)
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{
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results = PQexec(pset.db, "BEGIN");
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OK = AcceptResult(results) &&
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(PQresultStatus(results) == PGRES_COMMAND_OK);
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PQclear(results);
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if (!OK)
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return false;
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started_txn = true;
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}
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/* Send DECLARE CURSOR */
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initPQExpBuffer(&buf);
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appendPQExpBuffer(&buf, "DECLARE _psql_cursor NO SCROLL CURSOR FOR\n%s",
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query);
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results = PQexec(pset.db, buf.data);
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OK = AcceptResult(results) &&
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(PQresultStatus(results) == PGRES_COMMAND_OK);
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PQclear(results);
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termPQExpBuffer(&buf);
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if (!OK)
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goto cleanup;
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if (pset.timing)
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{
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GETTIMEOFDAY(&after);
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*elapsed_msec += DIFF_MSEC(&after, &before);
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}
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snprintf(fetch_cmd, sizeof(fetch_cmd),
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"FETCH FORWARD %d FROM _psql_cursor",
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pset.fetch_count);
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/* prepare to write output to \g argument, if any */
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if (pset.gfname)
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{
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/* keep this code in sync with PrintQueryTuples */
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pset.queryFout = stdout; /* so it doesn't get closed */
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/* open file/pipe */
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if (!setQFout(pset.gfname))
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{
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pset.queryFout = queryFout_copy;
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pset.queryFoutPipe = queryFoutPipe_copy;
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OK = false;
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goto cleanup;
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}
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}
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for (;;)
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{
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if (pset.timing)
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GETTIMEOFDAY(&before);
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/* get FETCH_COUNT tuples at a time */
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results = PQexec(pset.db, fetch_cmd);
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OK = AcceptResult(results) &&
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(PQresultStatus(results) == PGRES_TUPLES_OK);
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if (pset.timing)
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{
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GETTIMEOFDAY(&after);
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*elapsed_msec += DIFF_MSEC(&after, &before);
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}
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if (!OK)
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{
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PQclear(results);
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break;
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}
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ntuples = PQntuples(results);
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if (ntuples < pset.fetch_count)
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{
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/* this is the last result set, so allow footer decoration */
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my_popt.topt.stop_table = true;
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}
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else if (pset.queryFout == stdout && !did_pager)
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||||
{
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||||
/*
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||||
* If query requires multiple result sets, hack to ensure that
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||||
* only one pager instance is used for the whole mess
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*/
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||||
pset.queryFout = PageOutput(100000, my_popt.topt.pager);
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||||
did_pager = true;
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||||
}
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||||
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printQuery(results, &my_popt, pset.queryFout, pset.logfile);
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||||
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/* after the first result set, disallow header decoration */
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my_popt.topt.start_table = false;
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||||
my_popt.topt.prior_records += ntuples;
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||||
|
||||
PQclear(results);
|
||||
|
||||
if (ntuples < pset.fetch_count || cancel_pressed)
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||||
break;
|
||||
}
|
||||
|
||||
/* close \g argument file/pipe, restore old setting */
|
||||
if (pset.gfname)
|
||||
{
|
||||
/* keep this code in sync with PrintQueryTuples */
|
||||
setQFout(NULL);
|
||||
|
||||
pset.queryFout = queryFout_copy;
|
||||
pset.queryFoutPipe = queryFoutPipe_copy;
|
||||
|
||||
free(pset.gfname);
|
||||
pset.gfname = NULL;
|
||||
}
|
||||
else if (did_pager)
|
||||
{
|
||||
ClosePager(pset.queryFout);
|
||||
pset.queryFout = queryFout_copy;
|
||||
pset.queryFoutPipe = queryFoutPipe_copy;
|
||||
}
|
||||
|
||||
cleanup:
|
||||
if (pset.timing)
|
||||
GETTIMEOFDAY(&before);
|
||||
|
||||
/*
|
||||
* We try to close the cursor on either success or failure, but on
|
||||
* failure ignore the result (it's probably just a bleat about
|
||||
* being in an aborted transaction)
|
||||
*/
|
||||
results = PQexec(pset.db, "CLOSE _psql_cursor");
|
||||
if (OK)
|
||||
{
|
||||
OK = AcceptResult(results) &&
|
||||
(PQresultStatus(results) == PGRES_COMMAND_OK);
|
||||
}
|
||||
PQclear(results);
|
||||
|
||||
if (started_txn)
|
||||
{
|
||||
results = PQexec(pset.db, OK ? "COMMIT" : "ROLLBACK");
|
||||
OK &= AcceptResult(results) &&
|
||||
(PQresultStatus(results) == PGRES_COMMAND_OK);
|
||||
PQclear(results);
|
||||
}
|
||||
|
||||
if (pset.timing)
|
||||
{
|
||||
GETTIMEOFDAY(&after);
|
||||
*elapsed_msec += DIFF_MSEC(&after, &before);
|
||||
}
|
||||
|
||||
return OK;
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Advance the given char pointer over white space and SQL comments.
|
||||
*/
|
||||
|
|
@ -1158,6 +1371,43 @@ command_no_begin(const char *query)
|
|||
}
|
||||
|
||||
|
||||
/*
|
||||
* Check whether the specified command is a SELECT (or VALUES).
|
||||
*/
|
||||
static bool
|
||||
is_select_command(const char *query)
|
||||
{
|
||||
int wordlen;
|
||||
|
||||
/*
|
||||
* First advance over any whitespace, comments and left parentheses.
|
||||
*/
|
||||
for (;;)
|
||||
{
|
||||
query = skip_white_space(query);
|
||||
if (query[0] == '(')
|
||||
query++;
|
||||
else
|
||||
break;
|
||||
}
|
||||
|
||||
/*
|
||||
* Check word length (since "selectx" is not "select").
|
||||
*/
|
||||
wordlen = 0;
|
||||
while (isalpha((unsigned char) query[wordlen]))
|
||||
wordlen += PQmblen(&query[wordlen], pset.encoding);
|
||||
|
||||
if (wordlen == 6 && pg_strncasecmp(query, "select", 6) == 0)
|
||||
return true;
|
||||
|
||||
if (wordlen == 6 && pg_strncasecmp(query, "values", 6) == 0)
|
||||
return true;
|
||||
|
||||
return false;
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Test if the current user is a database superuser.
|
||||
*
|
||||
|
|
|
|||
1030
src/bin/psql/print.c
1030
src/bin/psql/print.c
File diff suppressed because it is too large
Load Diff
|
|
@ -3,7 +3,7 @@
|
|||
*
|
||||
* Copyright (c) 2000-2006, PostgreSQL Global Development Group
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/bin/psql/print.h,v 1.31 2006/03/05 15:58:51 momjian Exp $
|
||||
* $PostgreSQL: pgsql/src/bin/psql/print.h,v 1.32 2006/08/29 22:25:07 tgl Exp $
|
||||
*/
|
||||
#ifndef PRINT_H
|
||||
#define PRINT_H
|
||||
|
|
@ -12,6 +12,7 @@
|
|||
|
||||
|
||||
extern FILE *PageOutput(int lines, unsigned short int pager);
|
||||
extern void ClosePager(FILE *pagerpipe);
|
||||
|
||||
extern void html_escaped_print(const char *in, FILE *fout);
|
||||
|
||||
|
|
@ -32,11 +33,14 @@ typedef struct _printTableOpt
|
|||
enum printFormat format; /* one of the above */
|
||||
bool expanded; /* expanded/vertical output (if supported by
|
||||
* output format) */
|
||||
unsigned short int border; /* Print a border around the table. 0=none,
|
||||
* 1=dividing lines, 2=full */
|
||||
unsigned short int pager; /* use pager for output (if to stdout and
|
||||
* stdout is a tty) 0=off 1=on 2=always */
|
||||
bool tuples_only; /* don't output headers, row counts, etc. */
|
||||
unsigned short int border; /* Print a border around the table. 0=none,
|
||||
* 1=dividing lines, 2=full */
|
||||
bool start_table; /* print start decoration, eg <table> */
|
||||
bool stop_table; /* print stop decoration, eg </table> */
|
||||
unsigned long prior_records; /* start offset for record counters */
|
||||
char *fieldSep; /* field separator for unaligned text mode */
|
||||
char *recordSep; /* record separator for unaligned text mode */
|
||||
bool numericLocale; /* locale-aware numeric units separator and
|
||||
|
|
|
|||
|
|
@ -3,7 +3,7 @@
|
|||
*
|
||||
* Copyright (c) 2000-2006, PostgreSQL Global Development Group
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/bin/psql/settings.h,v 1.29 2006/08/29 15:19:51 tgl Exp $
|
||||
* $PostgreSQL: pgsql/src/bin/psql/settings.h,v 1.30 2006/08/29 22:25:07 tgl Exp $
|
||||
*/
|
||||
#ifndef SETTINGS_H
|
||||
#define SETTINGS_H
|
||||
|
|
@ -96,6 +96,7 @@ typedef struct _psqlSettings
|
|||
bool quiet;
|
||||
bool singleline;
|
||||
bool singlestep;
|
||||
int fetch_count;
|
||||
PSQL_ECHO echo;
|
||||
PSQL_ECHO_HIDDEN echo_hidden;
|
||||
PSQL_ERROR_ROLLBACK on_error_rollback;
|
||||
|
|
|
|||
|
|
@ -3,7 +3,7 @@
|
|||
*
|
||||
* Copyright (c) 2000-2006, PostgreSQL Global Development Group
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/bin/psql/startup.c,v 1.136 2006/08/29 15:19:51 tgl Exp $
|
||||
* $PostgreSQL: pgsql/src/bin/psql/startup.c,v 1.137 2006/08/29 22:25:08 tgl Exp $
|
||||
*/
|
||||
#include "postgres_fe.h"
|
||||
|
||||
|
|
@ -145,6 +145,8 @@ main(int argc, char *argv[])
|
|||
pset.popt.topt.format = PRINT_ALIGNED;
|
||||
pset.popt.topt.border = 1;
|
||||
pset.popt.topt.pager = 1;
|
||||
pset.popt.topt.start_table = true;
|
||||
pset.popt.topt.stop_table = true;
|
||||
pset.popt.default_footer = true;
|
||||
|
||||
pset.notty = (!isatty(fileno(stdin)) || !isatty(fileno(stdout)));
|
||||
|
|
@ -798,6 +800,12 @@ singlestep_hook(const char *newval)
|
|||
pset.singlestep = ParseVariableBool(newval);
|
||||
}
|
||||
|
||||
static void
|
||||
fetch_count_hook(const char *newval)
|
||||
{
|
||||
pset.fetch_count = ParseVariableNum(newval, -1, -1, false);
|
||||
}
|
||||
|
||||
static void
|
||||
echo_hook(const char *newval)
|
||||
{
|
||||
|
|
@ -899,6 +907,7 @@ EstablishVariableSpace(void)
|
|||
SetVariableAssignHook(pset.vars, "QUIET", quiet_hook);
|
||||
SetVariableAssignHook(pset.vars, "SINGLELINE", singleline_hook);
|
||||
SetVariableAssignHook(pset.vars, "SINGLESTEP", singlestep_hook);
|
||||
SetVariableAssignHook(pset.vars, "FETCH_COUNT", fetch_count_hook);
|
||||
SetVariableAssignHook(pset.vars, "ECHO", echo_hook);
|
||||
SetVariableAssignHook(pset.vars, "ECHO_HIDDEN", echo_hidden_hook);
|
||||
SetVariableAssignHook(pset.vars, "ON_ERROR_ROLLBACK", on_error_rollback_hook);
|
||||
|
|
|
|||
Loading…
Reference in New Issue