copy.c

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/*
 * psql - the PostgreSQL interactive terminal
 *
 * Copyright (c) 2000-2023, PostgreSQL Global Development Group
 *
 * src/bin/psql/copy.c
 */
#include "postgres_fe.h"
 
#include <signal.h>
#include <sys/stat.h>
#ifndef WIN32
#include <unistd.h>             /* for isatty */
#else
#include <io.h>                 /* I think */
#endif
 
#include "common.h"
#include "common/logging.h"
#include "copy.h"
#include "libpq-fe.h"
#include "pqexpbuffer.h"
#include "prompt.h"
#include "settings.h"
#include "stringutils.h"
 
/*
 * parse_slash_copy
 * -- parses \copy command line
 *
 * The documented syntax is:
 *  \copy tablename [(columnlist)] from|to filename [options]
 *  \copy ( query stmt ) to filename [options]
 *
 * where 'filename' can be one of the following:
 *  '<file path>' | PROGRAM '<command>' | stdin | stdout | pstdout | pstdout
 * and 'query' can be one of the following:
 *  SELECT | UPDATE | INSERT | DELETE
 *
 * An undocumented fact is that you can still write BINARY before the
 * tablename; this is a hangover from the pre-7.3 syntax.  The options
 * syntax varies across backend versions, but we avoid all that mess
 * by just transmitting the stuff after the filename literally.
 *
 * table name can be double-quoted and can have a schema part.
 * column names can be double-quoted.
 * filename can be single-quoted like SQL literals.
 * command must be single-quoted like SQL literals.
 *
 * returns a malloc'ed structure with the options, or NULL on parsing error
 */
 
struct copy_options
{
    char       *before_tofrom;  /* COPY string before TO/FROM */
    char       *after_tofrom;   /* COPY string after TO/FROM filename */
    char       *file;           /* NULL = stdin/stdout */
    bool        program;        /* is 'file' a program to popen? */
    bool        psql_inout;     /* true = use psql stdin/stdout */
    bool        from;           /* true = FROM, false = TO */
};
 
 
static void
free_copy_options(struct copy_options *ptr)
{
    if (!ptr)
        return;
    free(ptr->before_tofrom);
    free(ptr->after_tofrom);
    free(ptr->file);
    free(ptr);
}
 
 
/* concatenate "more" onto "var", freeing the original value of *var */
static void
xstrcat(char **var, const char *more)
{
    char       *newvar;
 
    newvar = psprintf("%s%s", *var, more);
    free(*var);
    *var = newvar;
}
 
 
static struct copy_options *
parse_slash_copy(const char *args)
{
    struct copy_options *result;
    char       *token;
    const char *whitespace = " \t\n\r";
    char        nonstd_backslash = standard_strings() ? 0 : '\\';
 
    if (!args)
    {
        pg_log_error("\\copy: arguments required");
        return NULL;
    }
 
    result = pg_malloc0(sizeof(struct copy_options));
 
    result->before_tofrom = pg_strdup("");  /* initialize for appending */
 
    token = strtokx(args, whitespace, ".,()", "\"",
                    0, false, false, pset.encoding);
    if (!token)
        goto error;
 
    /* The following can be removed when we drop 7.3 syntax support */
    if (pg_strcasecmp(token, "binary") == 0)
    {
        xstrcat(&result->before_tofrom, token);
        token = strtokx(NULL, whitespace, ".,()", "\"",
                        0, false, false, pset.encoding);
        if (!token)
            goto error;
    }
 
    /* Handle COPY (query) case */
    if (token[0] == '(')
    {
        int         parens = 1;
 
        while (parens > 0)
        {
            xstrcat(&result->before_tofrom, " ");
            xstrcat(&result->before_tofrom, token);
            token = strtokx(NULL, whitespace, "()", "\"'",
                            nonstd_backslash, true, false, pset.encoding);
            if (!token)
                goto error;
            if (token[0] == '(')
                parens++;
            else if (token[0] == ')')
                parens--;
        }
    }
 
    xstrcat(&result->before_tofrom, " ");
    xstrcat(&result->before_tofrom, token);
    token = strtokx(NULL, whitespace, ".,()", "\"",
                    0, false, false, pset.encoding);
    if (!token)
        goto error;
 
    /*
     * strtokx() will not have returned a multi-character token starting with
     * '.', so we don't need strcmp() here.  Likewise for '(', etc, below.
     */
    if (token[0] == '.')
    {
        /* handle schema . table */
        xstrcat(&result->before_tofrom, token);
        token = strtokx(NULL, whitespace, ".,()", "\"",
                        0, false, false, pset.encoding);
        if (!token)
            goto error;
        xstrcat(&result->before_tofrom, token);
        token = strtokx(NULL, whitespace, ".,()", "\"",
                        0, false, false, pset.encoding);
        if (!token)
            goto error;
    }
 
    if (token[0] == '(')
    {
        /* handle parenthesized column list */
        for (;;)
        {
            xstrcat(&result->before_tofrom, " ");
            xstrcat(&result->before_tofrom, token);
            token = strtokx(NULL, whitespace, "()", "\"",
                            0, false, false, pset.encoding);
            if (!token)
                goto error;
            if (token[0] == ')')
                break;
        }
        xstrcat(&result->before_tofrom, " ");
        xstrcat(&result->before_tofrom, token);
        token = strtokx(NULL, whitespace, ".,()", "\"",
                        0, false, false, pset.encoding);
        if (!token)
            goto error;
    }
 
    if (pg_strcasecmp(token, "from") == 0)
        result->from = true;
    else if (pg_strcasecmp(token, "to") == 0)
        result->from = false;
    else
        goto error;
 
    /* { 'filename' | PROGRAM 'command' | STDIN | STDOUT | PSTDIN | PSTDOUT } */
    token = strtokx(NULL, whitespace, ";", "'",
                    0, false, false, pset.encoding);
    if (!token)
        goto error;
 
    if (pg_strcasecmp(token, "program") == 0)
    {
        int         toklen;
 
        token = strtokx(NULL, whitespace, ";", "'",
                        0, false, false, pset.encoding);
        if (!token)
            goto error;
 
        /*
         * The shell command must be quoted. This isn't fool-proof, but
         * catches most quoting errors.
         */
        toklen = strlen(token);
        if (token[0] != '\'' || toklen < 2 || token[toklen - 1] != '\'')
            goto error;
 
        strip_quotes(token, '\'', 0, pset.encoding);
 
        result->program = true;
        result->file = pg_strdup(token);
    }
    else if (pg_strcasecmp(token, "stdin") == 0 ||
             pg_strcasecmp(token, "stdout") == 0)
    {
        result->file = NULL;
    }
    else if (pg_strcasecmp(token, "pstdin") == 0 ||
             pg_strcasecmp(token, "pstdout") == 0)
    {
        result->psql_inout = true;
        result->file = NULL;
    }
    else
    {
        /* filename can be optionally quoted */
        strip_quotes(token, '\'', 0, pset.encoding);
        result->file = pg_strdup(token);
        expand_tilde(&result->file);
    }
 
    /* Collect the rest of the line (COPY options) */
    token = strtokx(NULL, "", NULL, NULL,
                    0, false, false, pset.encoding);
    if (token)
        result->after_tofrom = pg_strdup(token);
 
    return result;
 
error:
    if (token)
        pg_log_error("\\copy: parse error at \"%s\"", token);
    else
        pg_log_error("\\copy: parse error at end of line");
    free_copy_options(result);
 
    return NULL;
}
 
 
/*
 * Execute a \copy command (frontend copy). We have to open a file (or execute
 * a command), then submit a COPY query to the backend and either feed it data
 * from the file or route its response into the file.
 */
bool
do_copy(const char *args)
{
    PQExpBufferData query;
    FILE       *copystream;
    struct copy_options *options;
    bool        success;
 
    /* parse options */
    options = parse_slash_copy(args);
 
    if (!options)
        return false;
 
    /* prepare to read or write the target file */
    if (options->file && !options->program)
        canonicalize_path(options->file);
 
    if (options->from)
    {
        if (options->file)
        {
            if (options->program)
            {
                fflush(NULL);
                errno = 0;
                copystream = popen(options->file, PG_BINARY_R);
            }
            else
                copystream = fopen(options->file, PG_BINARY_R);
        }
        else if (!options->psql_inout)
            copystream = pset.cur_cmd_source;
        else
            copystream = stdin;
    }
    else
    {
        if (options->file)
        {
            if (options->program)
            {
                fflush(NULL);
                disable_sigpipe_trap();
                errno = 0;
                copystream = popen(options->file, PG_BINARY_W);
            }
            else
                copystream = fopen(options->file, PG_BINARY_W);
        }
        else if (!options->psql_inout)
            copystream = pset.queryFout;
        else
            copystream = stdout;
    }
 
    if (!copystream)
    {
        if (options->program)
            pg_log_error("could not execute command \"%s\": %m",
                         options->file);
        else
            pg_log_error("%s: %m",
                         options->file);
        free_copy_options(options);
        return false;
    }
 
    if (!options->program)
    {
        struct stat st;
        int         result;
 
        /* make sure the specified file is not a directory */
        if ((result = fstat(fileno(copystream), &st)) < 0)
            pg_log_error("could not stat file \"%s\": %m",
                         options->file);
 
        if (result == 0 && S_ISDIR(st.st_mode))
            pg_log_error("%s: cannot copy from/to a directory",
                         options->file);
 
        if (result < 0 || S_ISDIR(st.st_mode))
        {
            fclose(copystream);
            free_copy_options(options);
            return false;
        }
    }
 
    /* build the command we will send to the backend */
    initPQExpBuffer(&query);
    printfPQExpBuffer(&query, "COPY ");
    appendPQExpBufferStr(&query, options->before_tofrom);
    if (options->from)
        appendPQExpBufferStr(&query, " FROM STDIN ");
    else
        appendPQExpBufferStr(&query, " TO STDOUT ");
    if (options->after_tofrom)
        appendPQExpBufferStr(&query, options->after_tofrom);
 
    /* run it like a user command, but with copystream as data source/sink */
    pset.copyStream = copystream;
    success = SendQuery(query.data);
    pset.copyStream = NULL;
    termPQExpBuffer(&query);
 
    if (options->file != NULL)
    {
        if (options->program)
        {
            int         pclose_rc = pclose(copystream);
 
            if (pclose_rc != 0)
            {
                if (pclose_rc < 0)
                    pg_log_error("could not close pipe to external command: %m");
                else
                {
                    char       *reason = wait_result_to_str(pclose_rc);
 
                    pg_log_error("%s: %s", options->file,
                                 reason ? reason : "");
                    free(reason);
                }
                success = false;
            }
            SetShellResultVariables(pclose_rc);
            restore_sigpipe_trap();
        }
        else
        {
            if (fclose(copystream) != 0)
            {
                pg_log_error("%s: %m", options->file);
                success = false;
            }
        }
    }
    free_copy_options(options);
    return success;
}
 
 
/*
 * Functions for handling COPY IN/OUT data transfer.
 *
 * If you want to use COPY TO STDOUT/FROM STDIN in your application,
 * this is the code to steal ;)
 */
 
/*
 * handleCopyOut
 * receives data as a result of a COPY ... TO STDOUT command
 *
 * conn should be a database connection that you just issued COPY TO on
 * and got back a PGRES_COPY_OUT result.
 *
 * copystream is the file stream for the data to go to.
 * copystream can be NULL to eat the data without writing it anywhere.
 *
 * The final status for the COPY is returned into *res (but note
 * we already reported the error, if it's not a success result).
 *
 * result is true if successful, false if not.
 */
bool
handleCopyOut(PGconn *conn, FILE *copystream, PGresult **res)
{
    bool        OK = true;
    char       *buf;
    int         ret;
 
    for (;;)
    {
        ret = PQgetCopyData(conn, &buf, 0);
 
        if (ret < 0)
            break;              /* done or server/connection error */
 
        if (buf)
        {
            if (OK && copystream && fwrite(buf, 1, ret, copystream) != ret)
            {
                pg_log_error("could not write COPY data: %m");
                /* complain only once, keep reading data from server */
                OK = false;
            }
            PQfreemem(buf);
        }
    }
 
    if (OK && copystream && fflush(copystream))
    {
        pg_log_error("could not write COPY data: %m");
        OK = false;
    }
 
    if (ret == -2)
    {
        pg_log_error("COPY data transfer failed: %s", PQerrorMessage(conn));
        OK = false;
    }
 
    /*
     * Check command status and return to normal libpq state.
     *
     * If for some reason libpq is still reporting PGRES_COPY_OUT state, we
     * would like to forcibly exit that state, since our caller would be
     * unable to distinguish that situation from reaching the next COPY in a
     * command string that happened to contain two consecutive COPY TO STDOUT
     * commands.  However, libpq provides no API for doing that, and in
     * principle it's a libpq bug anyway if PQgetCopyData() returns -1 or -2
     * but hasn't exited COPY_OUT state internally.  So we ignore the
     * possibility here.
     */
    *res = PQgetResult(conn);
    if (PQresultStatus(*res) != PGRES_COMMAND_OK)
    {
        pg_log_info("%s", PQerrorMessage(conn));
        OK = false;
    }
 
    return OK;
}
 
/*
 * handleCopyIn
 * sends data to complete a COPY ... FROM STDIN command
 *
 * conn should be a database connection that you just issued COPY FROM on
 * and got back a PGRES_COPY_IN result.
 * copystream is the file stream to read the data from.
 * isbinary can be set from PQbinaryTuples().
 * The final status for the COPY is returned into *res (but note
 * we already reported the error, if it's not a success result).
 *
 * result is true if successful, false if not.
 */
 
/* read chunk size for COPY IN - size is not critical */
#define COPYBUFSIZ 8192
 
bool
handleCopyIn(PGconn *conn, FILE *copystream, bool isbinary, PGresult **res)
{
    bool        OK;
    char        buf[COPYBUFSIZ];
    bool        showprompt;
 
    /*
     * Establish longjmp destination for exiting from wait-for-input. (This is
     * only effective while sigint_interrupt_enabled is TRUE.)
     */
    if (sigsetjmp(sigint_interrupt_jmp, 1) != 0)
    {
        /* got here with longjmp */
 
        /* Terminate data transfer */
        PQputCopyEnd(conn,
                     (PQprotocolVersion(conn) < 3) ? NULL :
                     _("canceled by user"));
 
        OK = false;
        goto copyin_cleanup;
    }
 
    /* Prompt if interactive input */
    if (isatty(fileno(copystream)))
    {
        showprompt = true;
        if (!pset.quiet)
            puts(_("Enter data to be copied followed by a newline.\n"
                   "End with a backslash and a period on a line by itself, or an EOF signal."));
    }
    else
        showprompt = false;
 
    OK = true;
 
    if (isbinary)
    {
        /* interactive input probably silly, but give one prompt anyway */
        if (showprompt)
        {
            const char *prompt = get_prompt(PROMPT_COPY, NULL);
 
            fputs(prompt, stdout);
            fflush(stdout);
        }
 
        for (;;)
        {
            int         buflen;
 
            /* enable longjmp while waiting for input */
            sigint_interrupt_enabled = true;
 
            buflen = fread(buf, 1, COPYBUFSIZ, copystream);
 
            sigint_interrupt_enabled = false;
 
            if (buflen <= 0)
                break;
 
            if (PQputCopyData(conn, buf, buflen) <= 0)
            {
                OK = false;
                break;
            }
        }
    }
    else
    {
        bool        copydone = false;
        int         buflen;
        bool        at_line_begin = true;
 
        /*
         * In text mode, we have to read the input one line at a time, so that
         * we can stop reading at the EOF marker (\.).  We mustn't read beyond
         * the EOF marker, because if the data was inlined in a SQL script, we
         * would eat up the commands after the EOF marker.
         */
        buflen = 0;
        while (!copydone)
        {
            char       *fgresult;
 
            if (at_line_begin && showprompt)
            {
                const char *prompt = get_prompt(PROMPT_COPY, NULL);
 
                fputs(prompt, stdout);
                fflush(stdout);
            }
 
            /* enable longjmp while waiting for input */
            sigint_interrupt_enabled = true;
 
            fgresult = fgets(&buf[buflen], COPYBUFSIZ - buflen, copystream);
 
            sigint_interrupt_enabled = false;
 
            if (!fgresult)
                copydone = true;
            else
            {
                int         linelen;
 
                linelen = strlen(fgresult);
                buflen += linelen;
 
                /* current line is done? */
                if (buf[buflen - 1] == '\n')
                {
                    /* check for EOF marker, but not on a partial line */
                    if (at_line_begin)
                    {
                        /*
                         * This code erroneously assumes '\.' on a line alone
                         * inside a quoted CSV string terminates the \copy.
                         * https://www.postgresql.org/message-id/E1TdNVQ-0001ju-GO@wrigleys.postgresql.org
                         *
                         * https://www.postgresql.org/message-id/bfcd57e4-8f23-4c3e-a5db-2571d09208e2@beta.fastmail.com
                         */
                        if ((linelen == 3 && memcmp(fgresult, "\\.\n", 3) == 0) ||
                            (linelen == 4 && memcmp(fgresult, "\\.\r\n", 4) == 0))
                        {
                            copydone = true;
                        }
                    }
 
                    if (copystream == pset.cur_cmd_source)
                    {
                        pset.lineno++;
                        pset.stmt_lineno++;
                    }
                    at_line_begin = true;
                }
                else
                    at_line_begin = false;
            }
 
            /*
             * If the buffer is full, or we've reached the EOF, flush it.
             *
             * Make sure there's always space for four more bytes in the
             * buffer, plus a NUL terminator.  That way, an EOF marker is
             * never split across two fgets() calls, which simplifies the
             * logic.
             */
            if (buflen >= COPYBUFSIZ - 5 || (copydone && buflen > 0))
            {
                if (PQputCopyData(conn, buf, buflen) <= 0)
                {
                    OK = false;
                    break;
                }
 
                buflen = 0;
            }
        }
    }
 
    /* Check for read error */
    if (ferror(copystream))
        OK = false;
 
    /*
     * Terminate data transfer.  We can't send an error message if we're using
     * protocol version 2.  (libpq no longer supports protocol version 2, but
     * keep the version checks just in case you're using a pre-v14 libpq.so at
     * runtime)
     */
    if (PQputCopyEnd(conn,
                     (OK || PQprotocolVersion(conn) < 3) ? NULL :
                     _("aborted because of read failure")) <= 0)
        OK = false;
 
copyin_cleanup:
 
    /*
     * Clear the EOF flag on the stream, in case copying ended due to an EOF
     * signal.  This allows an interactive TTY session to perform another COPY
     * FROM STDIN later.  (In non-STDIN cases, we're about to close the file
     * anyway, so it doesn't matter.)  Although we don't ever test the flag
     * with feof(), some fread() implementations won't read more data if it's
     * set.  This also clears the error flag, but we already checked that.
     */
    clearerr(copystream);
 
    /*
     * Check command status and return to normal libpq state.
     *
     * We do not want to return with the status still PGRES_COPY_IN: our
     * caller would be unable to distinguish that situation from reaching the
     * next COPY in a command string that happened to contain two consecutive
     * COPY FROM STDIN commands.  We keep trying PQputCopyEnd() in the hope
     * it'll work eventually.  (What's actually likely to happen is that in
     * attempting to flush the data, libpq will eventually realize that the
     * connection is lost.  But that's fine; it will get us out of COPY_IN
     * state, which is what we need.)
     */
    while (*res = PQgetResult(conn), PQresultStatus(*res) == PGRES_COPY_IN)
    {
        OK = false;
        PQclear(*res);
        /* We can't send an error message if we're using protocol version 2 */
        PQputCopyEnd(conn,
                     (PQprotocolVersion(conn) < 3) ? NULL :
                     _("trying to exit copy mode"));
    }
    if (PQresultStatus(*res) != PGRES_COMMAND_OK)
    {
        pg_log_info("%s", PQerrorMessage(conn));
        OK = false;
    }
 
    return OK;
}