| PostgreSQL 9.5.25 Documentation | |||
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ecpg can be run in a so-called Informix compatibility mode. If this mode is active, it tries to behave as if it were the Informix precompiler for Informix E/SQL. Generally spoken this will allow you to use the dollar sign instead of the EXEC SQL primitive to introduce embedded SQL commands:
$int j = 3; $CONNECT TO :dbname; $CREATE TABLE test(i INT PRIMARY KEY, j INT); $INSERT INTO test(i, j) VALUES (7, :j); $COMMIT;
Note: There must not be any white space between the $ and a following preprocessor directive, that is, include, define, ifdef, etc. Otherwise, the preprocessor will parse the token as a host variable.
There are two compatibility modes: INFORMIX, INFORMIX_SE
When linking programs that use this compatibility mode, remember to link against libcompat that is shipped with ECPG.
Besides the previously explained syntactic sugar, the Informix compatibility mode ports some functions for input, output and transformation of data as well as embedded SQL statements known from E/SQL to ECPG.
Informix compatibility mode is closely connected to the pgtypeslib library of ECPG. pgtypeslib maps SQL data types to data types within the C host program and most of the additional functions of the Informix compatibility mode allow you to operate on those C host program types. Note however that the extent of the compatibility is limited. It does not try to copy Informix behavior; it allows you to do more or less the same operations and gives you functions that have the same name and the same basic behavior but it is no drop-in replacement if you are using Informix at the moment. Moreover, some of the data types are different. For example, PostgreSQL's datetime and interval types do not know about ranges like for example YEAR TO MINUTE so you won't find support in ECPG for that either.
The Informix-special "string" pseudo-type for storing right-trimmed character string data is now supported in Informix-mode without using typedef. In fact, in Informix-mode, ECPG refuses to process source files that contain typedef sometype string;
EXEC SQL BEGIN DECLARE SECTION; string userid; /* this variable will contain trimmed data */ EXEC SQL END DECLARE SECTION; EXEC SQL FETCH MYCUR INTO :userid;
This statement closes the current connection. In fact, this is a synonym for ECPG's DISCONNECT CURRENT:
$CLOSE DATABASE; /* close the current connection */ EXEC SQL CLOSE DATABASE;
Due to the differences how ECPG works compared to Informix's ESQL/C (i.e., which steps are purely grammar transformations and which steps rely on the underlying run-time library) there is no FREE cursor_name statement in ECPG. This is because in ECPG, DECLARE CURSOR doesn't translate to a function call into the run-time library that uses to the cursor name. This means that there's no run-time bookkeeping of SQL cursors in the ECPG run-time library, only in the PostgreSQL server.
FREE statement_name is a synonym for DEALLOCATE PREPARE statement_name.
Informix-compatible mode supports a different structure than the one described in Section 33.7.2. See below:
struct sqlvar_compat
{
short sqltype;
int sqllen;
char *sqldata;
short *sqlind;
char *sqlname;
char *sqlformat;
short sqlitype;
short sqlilen;
char *sqlidata;
int sqlxid;
char *sqltypename;
short sqltypelen;
short sqlownerlen;
short sqlsourcetype;
char *sqlownername;
int sqlsourceid;
char *sqlilongdata;
int sqlflags;
void *sqlreserved;
};
struct sqlda_compat
{
short sqld;
struct sqlvar_compat *sqlvar;
char desc_name[19];
short desc_occ;
struct sqlda_compat *desc_next;
void *reserved;
};
typedef struct sqlvar_compat sqlvar_t;
typedef struct sqlda_compat sqlda_t;
The global properties are:
The number of fields in the SQLDA descriptor.
Pointer to the per-field properties.
Unused, filled with zero-bytes.
Size of the allocated structure.
Pointer to the next SQLDA structure if the result set contains more than one record.
Unused pointer, contains NULL. Kept for Informix-compatibility.
The per-field properties are below, they are stored in the sqlvar array:
Type of the field. Constants are in sqltypes.h
Length of the field data.
Pointer to the field data. The pointer is of char * type, the data pointed by it is in a binary format. Example:
int intval;
switch (sqldata->sqlvar[i].sqltype)
{
case SQLINTEGER:
intval = *(int *)sqldata->sqlvar[i].sqldata;
break;
...
}Pointer to the NULL indicator. If returned by DESCRIBE or FETCH then it's always a valid pointer. If used as input for EXECUTE ... USING sqlda; then NULL-pointer value means that the value for this field is non-NULL. Otherwise a valid pointer and sqlitype has to be properly set. Example:
if (*(int2 *)sqldata->sqlvar[i].sqlind != 0)
printf("value is NULL\n");Name of the field. 0-terminated string.
Reserved in Informix, value of PQfformat() for the field.
Type of the NULL indicator data. It's always SQLSMINT when returning data from the server. When the SQLDA is used for a parametrized query, the data is treated according to the set type.
Length of the NULL indicator data.
Extended type of the field, result of PQftype().
Unused.
It equals to sqldata if sqllen is larger than 32KB.
Example:
EXEC SQL INCLUDE sqlda.h;
sqlda_t *sqlda; /* This doesn't need to be under embedded DECLARE SECTION */
EXEC SQL BEGIN DECLARE SECTION;
char *prep_stmt = "select * from table1";
int i;
EXEC SQL END DECLARE SECTION;
...
EXEC SQL PREPARE mystmt FROM :prep_stmt;
EXEC SQL DESCRIBE mystmt INTO sqlda;
printf("# of fields: %d\n", sqlda->sqld);
for (i = 0; i < sqlda->sqld; i++)
printf("field %d: \"%s\"\n", sqlda->sqlvar[i]->sqlname);
EXEC SQL DECLARE mycursor CURSOR FOR mystmt;
EXEC SQL OPEN mycursor;
EXEC SQL WHENEVER NOT FOUND GOTO out;
while (1)
{
EXEC SQL FETCH mycursor USING sqlda;
}
EXEC SQL CLOSE mycursor;
free(sqlda); /* The main structure is all to be free(),
* sqlda and sqlda->sqlvar is in one allocated area */
For more information, see the sqlda.h header and the src/interfaces/ecpg/test/compat_informix/sqlda.pgc regression test.
decaddAdd two decimal type values.
int decadd(decimal *arg1, decimal *arg2, decimal *sum);
The function receives a pointer to the first operand of type decimal (arg1), a pointer to the second operand of type decimal (arg2) and a pointer to a value of type decimal that will contain the sum (sum). On success, the function returns 0. ECPG_INFORMIX_NUM_OVERFLOW is returned in case of overflow and ECPG_INFORMIX_NUM_UNDERFLOW in case of underflow. -1 is returned for other failures and errno is set to the respective errno number of the pgtypeslib.
deccmpCompare two variables of type decimal.
int deccmp(decimal *arg1, decimal *arg2);
The function receives a pointer to the first decimal value (arg1), a pointer to the second decimal value (arg2) and returns an integer value that indicates which is the bigger value.
1, if the value that arg1 points to is bigger than the value that var2 points to
-1, if the value that arg1 points to is smaller than the value that arg2 points to
0, if the value that arg1 points to and the value that arg2 points to are equal
deccopyCopy a decimal value.
void deccopy(decimal *src, decimal *target);
The function receives a pointer to the decimal value that should be copied as the first argument (src) and a pointer to the target structure of type decimal (target) as the second argument.
deccvascConvert a value from its ASCII representation into a decimal type.
int deccvasc(char *cp, int len, decimal *np);
The function receives a pointer to string that contains the string representation of the number to be converted (cp) as well as its length len. np is a pointer to the decimal value that saves the result of the operation.
Valid formats are for example: -2, .794, +3.44, 592.49E07 or -32.84e-4.
The function returns 0 on success. If overflow or underflow occurred, ECPG_INFORMIX_NUM_OVERFLOW or ECPG_INFORMIX_NUM_UNDERFLOW is returned. If the ASCII representation could not be parsed, ECPG_INFORMIX_BAD_NUMERIC is returned or ECPG_INFORMIX_BAD_EXPONENT if this problem occurred while parsing the exponent.
deccvdblConvert a value of type double to a value of type decimal.
int deccvdbl(double dbl, decimal *np);
The function receives the variable of type double that should be converted as its first argument (dbl). As the second argument (np), the function receives a pointer to the decimal variable that should hold the result of the operation.
The function returns 0 on success and a negative value if the conversion failed.
deccvintConvert a value of type int to a value of type decimal.
int deccvint(int in, decimal *np);
The function receives the variable of type int that should be converted as its first argument (in). As the second argument (np), the function receives a pointer to the decimal variable that should hold the result of the operation.
The function returns 0 on success and a negative value if the conversion failed.
deccvlongConvert a value of type long to a value of type decimal.
int deccvlong(long lng, decimal *np);
The function receives the variable of type long that should be converted as its first argument (lng). As the second argument (np), the function receives a pointer to the decimal variable that should hold the result of the operation.
The function returns 0 on success and a negative value if the conversion failed.
decdivDivide two variables of type decimal.
int decdiv(decimal *n1, decimal *n2, decimal *result);
The function receives pointers to the variables that are the first (n1) and the second (n2) operands and calculates n1/n2. result is a pointer to the variable that should hold the result of the operation.
On success, 0 is returned and a negative value if the division fails. If overflow or underflow occurred, the function returns ECPG_INFORMIX_NUM_OVERFLOW or ECPG_INFORMIX_NUM_UNDERFLOW respectively. If an attempt to divide by zero is observed, the function returns ECPG_INFORMIX_DIVIDE_ZERO.
decmulMultiply two decimal values.
int decmul(decimal *n1, decimal *n2, decimal *result);
The function receives pointers to the variables that are the first (n1) and the second (n2) operands and calculates n1*n2. result is a pointer to the variable that should hold the result of the operation.
On success, 0 is returned and a negative value if the multiplication fails. If overflow or underflow occurred, the function returns ECPG_INFORMIX_NUM_OVERFLOW or ECPG_INFORMIX_NUM_UNDERFLOW respectively.
decsubSubtract one decimal value from another.
int decsub(decimal *n1, decimal *n2, decimal *result);
The function receives pointers to the variables that are the first (n1) and the second (n2) operands and calculates n1-n2. result is a pointer to the variable that should hold the result of the operation.
On success, 0 is returned and a negative value if the subtraction fails. If overflow or underflow occurred, the function returns ECPG_INFORMIX_NUM_OVERFLOW or ECPG_INFORMIX_NUM_UNDERFLOW respectively.
dectoascConvert a variable of type decimal to its ASCII representation in a C char* string.
int dectoasc(decimal *np, char *cp, int len, int right)
The function receives a pointer to a variable of type decimal (np) that it converts to its textual representation. cp is the buffer that should hold the result of the operation. The parameter right specifies, how many digits right of the decimal point should be included in the output. The result will be rounded to this number of decimal digits. Setting right to -1 indicates that all available decimal digits should be included in the output. If the length of the output buffer, which is indicated by len is not sufficient to hold the textual representation including the trailing zero byte, only a single * character is stored in the result and -1 is returned.
The function returns either -1 if the buffer cp was too small or ECPG_INFORMIX_OUT_OF_MEMORY if memory was exhausted.
dectodblConvert a variable of type decimal to a double.
int dectodbl(decimal *np, double *dblp);
The function receives a pointer to the decimal value to convert (np) and a pointer to the double variable that should hold the result of the operation (dblp).
On success, 0 is returned and a negative value if the conversion failed.
dectointConvert a variable to type decimal to an integer.
int dectoint(decimal *np, int *ip);
The function receives a pointer to the decimal value to convert (np) and a pointer to the integer variable that should hold the result of the operation (ip).
On success, 0 is returned and a negative value if the conversion failed. If an overflow occurred, ECPG_INFORMIX_NUM_OVERFLOW is returned.
Note that the ECPG implementation differs from the Informix implementation. Informix limits an integer to the range from -32767 to 32767, while the limits in the ECPG implementation depend on the architecture (-INT_MAX .. INT_MAX).
dectolongConvert a variable to type decimal to a long integer.
int dectolong(decimal *np, long *lngp);
The function receives a pointer to the decimal value to convert (np) and a pointer to the long variable that should hold the result of the operation (lngp).
On success, 0 is returned and a negative value if the conversion failed. If an overflow occurred, ECPG_INFORMIX_NUM_OVERFLOW is returned.
Note that the ECPG implementation differs from the Informix implementation. Informix limits a long integer to the range from -2,147,483,647 to 2,147,483,647, while the limits in the ECPG implementation depend on the architecture (-LONG_MAX .. LONG_MAX).
rdatestrConverts a date to a C char* string.
int rdatestr(date d, char *str);
The function receives two arguments, the first one is the date to convert (d) and the second one is a pointer to the target string. The output format is always yyyy-mm-dd, so you need to allocate at least 11 bytes (including the zero-byte terminator) for the string.
The function returns 0 on success and a negative value in case of error.
Note that ECPG's implementation differs from the Informix implementation. In Informix the format can be influenced by setting environment variables. In ECPG however, you cannot change the output format.
rstrdateParse the textual representation of a date.
int rstrdate(char *str, date *d);
The function receives the textual representation of the date to convert (str) and a pointer to a variable of type date (d). This function does not allow you to specify a format mask. It uses the default format mask of Informix which is mm/dd/yyyy. Internally, this function is implemented by means of rdefmtdate. Therefore, rstrdate is not faster and if you have the choice you should opt for rdefmtdate which allows you to specify the format mask explicitly.
The function returns the same values as rdefmtdate.
rtodayGet the current date.
void rtoday(date *d);
The function receives a pointer to a date variable (d) that it sets to the current date.
Internally this function uses the PGTYPESdate_today function.
rjulmdyExtract the values for the day, the month and the year from a variable of type date.
int rjulmdy(date d, short mdy[3]);
The function receives the date d and a pointer to an array of 3 short integer values mdy. The variable name indicates the sequential order: mdy[0] will be set to contain the number of the month, mdy[1] will be set to the value of the day and mdy[2] will contain the year.
The function always returns 0 at the moment.
Internally the function uses the PGTYPESdate_julmdy function.
rdefmtdateUse a format mask to convert a character string to a value of type date.
int rdefmtdate(date *d, char *fmt, char *str);
The function receives a pointer to the date value that should hold the result of the operation (d), the format mask to use for parsing the date (fmt) and the C char* string containing the textual representation of the date (str). The textual representation is expected to match the format mask. However you do not need to have a 1:1 mapping of the string to the format mask. The function only analyzes the sequential order and looks for the literals yy or yyyy that indicate the position of the year, mm to indicate the position of the month and dd to indicate the position of the day.
The function returns the following values:
0 - The function terminated successfully.
ECPG_INFORMIX_ENOSHORTDATE - The date does not contain delimiters between day, month and year. In this case the input string must be exactly 6 or 8 bytes long but isn't.
ECPG_INFORMIX_ENOTDMY - The format string did not correctly indicate the sequential order of year, month and day.
ECPG_INFORMIX_BAD_DAY - The input string does not contain a valid day.
ECPG_INFORMIX_BAD_MONTH - The input string does not contain a valid month.
ECPG_INFORMIX_BAD_YEAR - The input string does not contain a valid year.
Internally this function is implemented to use the PGTYPESdate_defmt_asc function. See the reference there for a table of example input.
rfmtdateConvert a variable of type date to its textual representation using a format mask.
int rfmtdate(date d, char *fmt, char *str);
The function receives the date to convert (d), the format mask (fmt) and the string that will hold the textual representation of the date (str).
On success, 0 is returned and a negative value if an error occurred.
Internally this function uses the PGTYPESdate_fmt_asc function, see the reference there for examples.
rmdyjulCreate a date value from an array of 3 short integers that specify the day, the month and the year of the date.
int rmdyjul(short mdy[3], date *d);
The function receives the array of the 3 short integers (mdy) and a pointer to a variable of type date that should hold the result of the operation.
Currently the function returns always 0.
Internally the function is implemented to use the function PGTYPESdate_mdyjul.
rdayofweekReturn a number representing the day of the week for a date value.
int rdayofweek(date d);
The function receives the date variable d as its only argument and returns an integer that indicates the day of the week for this date.
0 - Sunday
1 - Monday
2 - Tuesday
3 - Wednesday
4 - Thursday
5 - Friday
6 - Saturday
Internally the function is implemented to use the function PGTYPESdate_dayofweek.
dtcurrentRetrieve the current timestamp.
void dtcurrent(timestamp *ts);
The function retrieves the current timestamp and saves it into the timestamp variable that ts points to.
dtcvascParses a timestamp from its textual representation into a timestamp variable.
int dtcvasc(char *str, timestamp *ts);
The function receives the string to parse (str) and a pointer to the timestamp variable that should hold the result of the operation (ts).
The function returns 0 on success and a negative value in case of error.
Internally this function uses the PGTYPEStimestamp_from_asc function. See the reference there for a table with example inputs.
dtcvfmtascParses a timestamp from its textual representation using a format mask into a timestamp variable.
dtcvfmtasc(char *inbuf, char *fmtstr, timestamp *dtvalue)
The function receives the string to parse (inbuf), the format mask to use (fmtstr) and a pointer to the timestamp variable that should hold the result of the operation (dtvalue).
This function is implemented by means of the PGTYPEStimestamp_defmt_asc function. See the documentation there for a list of format specifiers that can be used.
The function returns 0 on success and a negative value in case of error.
dtsubSubtract one timestamp from another and return a variable of type interval.
int dtsub(timestamp *ts1, timestamp *ts2, interval *iv);
The function will subtract the timestamp variable that ts2 points to from the timestamp variable that ts1 points to and will store the result in the interval variable that iv points to.
Upon success, the function returns 0 and a negative value if an error occurred.
dttoascConvert a timestamp variable to a C char* string.
int dttoasc(timestamp *ts, char *output);
The function receives a pointer to the timestamp variable to convert (ts) and the string that should hold the result of the operation (output). It converts ts to its textual representation according to the SQL standard, which is be YYYY-MM-DD HH:MM:SS.
Upon success, the function returns 0 and a negative value if an error occurred.
dttofmtascConvert a timestamp variable to a C char* using a format mask.
int dttofmtasc(timestamp *ts, char *output, int str_len, char *fmtstr);
The function receives a pointer to the timestamp to convert as its first argument (ts), a pointer to the output buffer (output), the maximal length that has been allocated for the output buffer (str_len) and the format mask to use for the conversion (fmtstr).
Upon success, the function returns 0 and a negative value if an error occurred.
Internally, this function uses the PGTYPEStimestamp_fmt_asc function. See the reference there for information on what format mask specifiers can be used.
intoascConvert an interval variable to a C char* string.
int intoasc(interval *i, char *str);
The function receives a pointer to the interval variable to convert (i) and the string that should hold the result of the operation (str). It converts i to its textual representation according to the SQL standard, which is be YYYY-MM-DD HH:MM:SS.
Upon success, the function returns 0 and a negative value if an error occurred.
rfmtlongConvert a long integer value to its textual representation using a format mask.
int rfmtlong(long lng_val, char *fmt, char *outbuf);
The function receives the long value lng_val, the format mask fmt and a pointer to the output buffer outbuf. It converts the long value according to the format mask to its textual representation.
The format mask can be composed of the following format specifying characters:
* (asterisk) - if this position would be blank otherwise, fill it with an asterisk.
& (ampersand) - if this position would be blank otherwise, fill it with a zero.
# - turn leading zeroes into blanks.
< - left-justify the number in the string.
, (comma) - group numbers of four or more digits into groups of three digits separated by a comma.
. (period) - this character separates the whole-number part of the number from the fractional part.
- (minus) - the minus sign appears if the number is a negative value.
+ (plus) - the plus sign appears if the number is a positive value.
( - this replaces the minus sign in front of the negative number. The minus sign will not appear.
) - this character replaces the minus and is printed behind the negative value.
$ - the currency symbol.
rupshiftConvert a string to upper case.
void rupshift(char *str);
The function receives a pointer to the string and transforms every lower case character to upper case.
bylengReturn the number of characters in a string without counting trailing blanks.
int byleng(char *str, int len);
The function expects a fixed-length string as its first argument (str) and its length as its second argument (len). It returns the number of significant characters, that is the length of the string without trailing blanks.
ldcharCopy a fixed-length string into a null-terminated string.
void ldchar(char *src, int len, char *dest);
The function receives the fixed-length string to copy (src), its length (len) and a pointer to the destination memory (dest). Note that you need to reserve at least len+1 bytes for the string that dest points to. The function copies at most len bytes to the new location (less if the source string has trailing blanks) and adds the null-terminator.
rgetmsgint rgetmsg(int msgnum, char *s, int maxsize);
This function exists but is not implemented at the moment!
rtypalignint rtypalign(int offset, int type);
This function exists but is not implemented at the moment!
rtypmsizeint rtypmsize(int type, int len);
This function exists but is not implemented at the moment!
rtypwidthint rtypwidth(int sqltype, int sqllen);
This function exists but is not implemented at the moment!
rsetnullSet a variable to NULL.
int rsetnull(int t, char *ptr);
The function receives an integer that indicates the type of the variable and a pointer to the variable itself that is cast to a C char* pointer.
The following types exist:
CCHARTYPE - For a variable of type char or char*
CSHORTTYPE - For a variable of type short int
CINTTYPE - For a variable of type int
CBOOLTYPE - For a variable of type boolean
CFLOATTYPE - For a variable of type float
CLONGTYPE - For a variable of type long
CDOUBLETYPE - For a variable of type double
CDECIMALTYPE - For a variable of type decimal
CDATETYPE - For a variable of type date
CDTIMETYPE - For a variable of type timestamp
Here is an example of a call to this function:
$char c[] = "abc "; $short s = 17; $int i = -74874; rsetnull(CCHARTYPE, (char *) c); rsetnull(CSHORTTYPE, (char *) &s); rsetnull(CINTTYPE, (char *) &i);
risnullTest if a variable is NULL.
int risnull(int t, char *ptr);
The function receives the type of the variable to test (t) as well a pointer to this variable (ptr). Note that the latter needs to be cast to a char*. See the function rsetnull for a list of possible variable types.
Here is an example of how to use this function:
$char c[] = "abc "; $short s = 17; $int i = -74874; risnull(CCHARTYPE, (char *) c); risnull(CSHORTTYPE, (char *) &s); risnull(CINTTYPE, (char *) &i);
Note that all constants here describe errors and all of them are defined to represent negative values. In the descriptions of the different constants you can also find the value that the constants represent in the current implementation. However you should not rely on this number. You can however rely on the fact all of them are defined to represent negative values.
Functions return this value if an overflow occurred in a calculation. Internally it is defined as -1200 (the Informix definition).
Functions return this value if an underflow occurred in a calculation. Internally it is defined as -1201 (the Informix definition).
Functions return this value if an attempt to divide by zero is observed. Internally it is defined as -1202 (the Informix definition).
Functions return this value if a bad value for a year was found while parsing a date. Internally it is defined as -1204 (the Informix definition).
Functions return this value if a bad value for a month was found while parsing a date. Internally it is defined as -1205 (the Informix definition).
Functions return this value if a bad value for a day was found while parsing a date. Internally it is defined as -1206 (the Informix definition).
Functions return this value if a parsing routine needs a short date representation but did not get the date string in the right length. Internally it is defined as -1209 (the Informix definition).
Functions return this value if an error occurred during date formatting. Internally it is defined as -1210 (the Informix definition).
Functions return this value if memory was exhausted during their operation. Internally it is defined as -1211 (the Informix definition).
Functions return this value if a parsing routine was supposed to get a format mask (like mmddyy) but not all fields were listed correctly. Internally it is defined as -1212 (the Informix definition).
Functions return this value either if a parsing routine cannot parse the textual representation for a numeric value because it contains errors or if a routine cannot complete a calculation involving numeric variables because at least one of the numeric variables is invalid. Internally it is defined as -1213 (the Informix definition).
Functions return this value if a parsing routine cannot parse an exponent. Internally it is defined as -1216 (the Informix definition).
Functions return this value if a parsing routine cannot parse a date. Internally it is defined as -1218 (the Informix definition).
Functions return this value if a parsing routine is passed extra characters it cannot parse. Internally it is defined as -1264 (the Informix definition).