Read ERN » 文本文件 http://www.readern.com 生命不息折腾不止 Sat, 31 Dec 2011 16:18:48 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 [重发]Pro*C实现导出Oracle表为文本文件 http://www.readern.com/export-oracle-table-to-flat-text-in-proc.html http://www.readern.com/export-oracle-table-to-flat-text-in-proc.html#comments Wed, 09 Sep 2009 00:49:32 +0000 ern http://www.readern.com/?p=157 旧文重发，原文刊载于2006年6月8日。

近日工作需要，要大批量导出数据，开始用SQL*Plus的SPOOL功能。结果老是提示“xrealloc: cannot reallocate XXX bytes”。而且每次发生的时间还不同，有时候是到文件1G就出错，有时候是2G多出错。怀疑是32位Linux问题，换到Solaris 8上还是如故。客户端都是9201的，到Metalink上搜索没有结果。郁闷之余到Oracle-l上发了个邮件，收到一位高手的指点，说可能是内存泄露问题，SQL*Plus的开发人员估计也不会想到有人会导出如此大量数据。在邮件往复之间，那位高手提醒可以用UTL_FILE来导出。忽然想起Tom的两本书里都有提到用PL/SQL来导出，于是翻出书里的那个网址http://asktom.oracle.com/~tkyte/flat/index.html，进去一看，PL/SQL的效率比SQL*Plus要高，缺点是生成的文件必须在主机上。SQL*Plus可以调整arraysize来提高效率（当然经我实践大数据量时还有内存泄露之虞）。Pro*C是高效的方法，缺点是需要写程序、编译。
硬着头皮看Pro*C咯，好在Tom给了原始代码，抓下来放到一台Linux的机器上proc报错，应该是proc配置include库的问题，找到一个makefile，倒是没啥问题了，但是最后链接失败，报无法识别’sqlca’。到网上一搜，和我一样晕的人还有，要修改代码，多include进，但是看Tom的帖子似乎没提到这个问题，不知道为什么。
下面是修改后的源代码，我顺便在里面修改了会话的一些参数，以处理中文和时间格式：

#include

#include

#include

#include

#define MAX_VNAME_LEN     30

#define MAX_INAME_LEN     30

static char *   USERID = NULL;

static char *   SQLSTMT = NULL;

static char *   ARRAY_SIZE = "10";

#define vstrcpy( a, b ) \

(strcpy( a.arr, b ), a.len = strlen( a.arr ), a.arr)

EXEC SQL INCLUDE SQLCA;

EXEC SQL INCLUDE sqlda;

extern SQLDA *sqlald();

extern void   sqlclu();

static void die( char * msg )

{

fprintf( stderr, "%s\n", msg );

exit(1);

}

/*

this array contains a default mapping

I am using to constrain the

lengths of returned columns.  It is mapping,

for example, the Oracle

NUMBER type (type code = 2) to be 45 characters

long in a string.

*/

static int lengths[] =

{ -1, 0, 45, 0, 0, 0, 0, 0, 2000, 0, 0,

18, 25, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 512, 2000 };

static void process_parms( argc, argv )

int    argc;

char *    argv[];

{

int    i;

for( i = 1; i < argc; i++ )

{

if ( !strncmp( argv[i], "userid=", 7 ) )

USERID = argv[i]+7;

else

if ( !strncmp( argv[i], "sqlstmt=", 8 ) )

SQLSTMT = argv[i]+8;

else

if ( !strncmp( argv[i], "arraysize=", 10 ) )

ARRAY_SIZE = argv[i]+10;

else

{

fprintf( stderr,

"usage: %s %s %s\n",

argv[0],

"userid=xxx/xxx sqlstmt=query ",

"arraysize=\n" );

exit(1);

}

}

if ( USERID == NULL  || SQLSTMT == NULL )

{

fprintf( stderr,

"usage: %s %s %s\n",

argv[0],

"userid=xxx/xxx sqlstmt=query ",

"arraysize=\n" );

exit(1);

}

}

static void sqlerror_hard()

{

EXEC SQL WHENEVER SQLERROR CONTINUE;

fprintf(stderr,"\nORACLE error detected:");

fprintf(stderr,"\n% .70s \n", sqlca.sqlerrm.sqlerrmc);

EXEC SQL ROLLBACK WORK RELEASE;

exit(1);

}

static SQLDA * process_1(char * sqlstmt, int array_size )

{

SQLDA *    select_dp;

int     i;

int        j;

int        null_ok;

int        precision;

int        scale;

int        size = 10;

fprintf( stderr, "Unloading '%s'\n", sqlstmt );

fprintf( stderr, "Array size = %d\n", array_size );

EXEC SQL WHENEVER SQLERROR DO sqlerror_hard();

EXEC SQL PREPARE S FROM :sqlstmt;

EXEC SQL DECLARE C CURSOR FOR S;

if ((select_dp = sqlald(size,MAX_VNAME_LEN,MAX_INAME_LEN))

== NULL )

die( "Cannot allocate  memory for select descriptor." );

select_dp->N = size;

EXEC SQL DESCRIBE SELECT LIST FOR S INTO select_dp;

if ( !select_dp->F ) return NULL;

if (select_dp->F < 0)     {         size = -select_dp->F;

sqlclu( select_dp );

if ((select_dp =

sqlald (size, MAX_VNAME_LEN, MAX_INAME_LEN))

== NULL )

die( "Cannot allocate  memory for descriptor." );

EXEC SQL DESCRIBE SELECT LIST FOR S INTO select_dp;

}

select_dp->N = select_dp->F;

for (i = 0; i < select_dp->N; i++)

select_dp->I[i] = (short *) malloc(sizeof(short) *

array_size );

for (i = 0; i < select_dp->F; i++)

{

sqlnul (&(select_dp->T[i]),

&(select_dp->T[i]), &null_ok);

if ( select_dp->T[i] <                      sizeof(lengths)/sizeof(lengths[0]) )         {             if ( lengths[select_dp->T[i]] )

select_dp->L[i]  = lengths[select_dp->T[i]];

else select_dp->L[i] += 5;

}

else select_dp->L[i] += 5;

select_dp->T[i] = 5;

select_dp->V[i] = (char *)malloc( select_dp->L[i] *

array_size );

for( j = MAX_VNAME_LEN-1;

j > 0 && select_dp->S[i][j] == ' ';

j--);

fprintf (stderr,

"%s%.*s", i?",":"", j+1, select_dp->S[i]);

}

fprintf( stderr, "\n" );

EXEC SQL OPEN C;

return select_dp;

}

static void process_2( SQLDA * select_dp, int array_size )

{

int    last_fetch_count;

int        row_count = 0;

short    ind_value;

char    * char_ptr;

int    i,

j;

for ( last_fetch_count = 0;

;

last_fetch_count = sqlca.sqlerrd[2] )

{

EXEC SQL FOR :array_size FETCH C

USING DESCRIPTOR select_dp;

for( j=0; j < sqlca.sqlerrd[2]-last_fetch_count; j++ )

{

for (i = 0; i < select_dp->F; i++)

{

ind_value = *(select_dp->I[i]+j);

char_ptr  = select_dp->V[i] +

(j*select_dp->L[i]);

printf( "%s%s", i?",":"",

ind_value?"(null)":char_ptr );

}

row_count++;

printf( "\n" );

}

if ( sqlca.sqlcode > 0 ) break;

}

sqlclu(select_dp);

EXEC SQL CLOSE C;

EXEC SQL COMMIT WORK;

fprintf( stderr, "%d rows extracted\n", row_count );

}

main( argc, argv )

int    argc;

char *    argv[];

{

EXEC SQL BEGIN DECLARE SECTION;

VARCHAR   oracleid[50];

EXEC SQL END DECLARE SECTION;

SQLDA    * select_dp;

process_parms( argc, argv );

/* Connect to ORACLE. */

vstrcpy( oracleid, USERID );

EXEC SQL WHENEVER SQLERROR DO sqlerror_hard();

EXEC SQL CONNECT :o racleid;

fprintf(stderr, "\nConnected to ORACLE as user: %s\n\n",

oracleid.arr);

EXEC SQL ALTER SESSION

SET NLS_DATE_FORMAT = 'YYYYMMDDHH24:MI:SS';

EXEC SQL ALTER SESSION

SET NLS_LANGUAGE = "SIMPLIFIED CHINESE";

select_dp = process_1( SQLSTMT, atoi(ARRAY_SIZE) );

process_2( select_dp , atoi(ARRAY_SIZE));

/* Disconnect from ORACLE. */

EXEC SQL COMMIT WORK RELEASE;

exit(0);

}

顺便附上我的makefile，在RHEL AS3上用的：

CC=gcc
LD=ld
OBJ=obj/

##########数据库编译选项###########
PROCFLAGS=unsafe_null=yes dynamic=ansi mode=oracle dbms=V8 parse=full\
release_cursor=no sqlcheck=SEMANTICS ireclen=512 include=./.\
sys_include=/usr/include sys_include=/usr/lib/gcc-lib/i386-redhat-linux/3.2.3/include \
def_sqlcode=yes

INCL=-I/usr/include -I./. -I${ORACLE_HOME}/precomp/public
BIN_LIBS= -lc -L${ORACLE_HOME}/lib -lclntsh

##########编译规则################
.SUFFIXES: .pc .o .c
.c.o:
${CC} -g -c $*.c ${INCL}

.pc.o:
proc $(PROCFLAGS) iname=$*.pc
$(CC) -g -c $*.c ${INCL}
rm -f $*.c $*.lis

all:unload

unload:unload.o
rm -f $@
${CC} -o $@ unload.o  \
$(BIN_LIBS)

#########################################################
#编译公用目标文件
#########################################################

########清理目标文件###########################
clean:
rm -f *.o *.lis

编译以后生成unload程序，执行如下：

unload userid=XXX/XXX sqlstmt='select * from dual' arraysize=100>XXX.DAT

这样DAT文件里就是数据了。

经我测试，在数据库主机上，30分钟导出了7GB的文件，强啊！效率上可以调整的一个是arraysize参数，这个一般100-200都可以，更大的除非你IO超强，不然也没有意义；另一个是所谓并行，其实这个C程序也就是执行SELECT语句，因此将原表改为PARALLEL就可以充分利用系统资源了^_^。

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