PostgreSQL C String to CHARACTER internal representation -

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I am trying to convert a C string to an internal representation of the character of PostgreSQL. I am using the varchar.c function in the bpcharin function. There are two arguments for this function: C string datum and atttypmod . It has been mentioned that the atttypmod type plus is the declared length of VARHDRSZ.

My conversion function is: 

  result = directfunction call 2 (bpcirin, csrringGetDatum (str), VARHDRSZ +?);   
 My string  str  value will be one of the columns datatype of my table. Therefore, I need the declared column data type length. This information is stored in the  character_maximum_length  in the  information_schema.column  view.  
 My question is, how do I get  character_maximum_length ? In C code?  
 Thank you.   
 
 
 Unless you are using the  char  data type You need  bpchar   CodeTringGetDatum  (for typed values ​​for  cstring ) or typed  CStringGetTextDatum  ( text ) Enough values) is enough.  
 
 It looks like you're   using  char (n) , that is,  bpchar . Frankly, the best thing to do  is not to do this ; This is a quirky type that should be replaced with a plain  text  or  varchar  in almost all cases.  
 If you should use it ... well, take a look at us at  pg_cast :  
  regress = & gt; C. *, From Tfrom.typname, f.proname pg_cast to c cctctunf = c on cg.procame, c on cachesource c txtom c.castource = tfrom.oid internally included pg_type tto c.casttarget = tto.oid left on the outer included pg_proc F. .oid where tto.typname = 'bpchar'; Hairdresser | Racial targets Castfunk | Castanetext | Consumption | Typname | | Proname ------------ + ------------ + ---------- + ------------ - + ------------ + --------- + --------- 25 | 1042 | 0 | I B Text | 1043 | 1042 | 0 | I B Varchar | | 18 | 1042 | 860 | One | F | Four Bept 19 1042 | 408 | One | F | Name | Bipcher 650 | 1042 | 730 | One | F | Cedar | Lesson 869 | 1042 | 730 | One | F | Inet | | Text16 | 1042 | 2971 | One | F | Bull | Lesson 142 | 1042 | 0 | One | B Xml | 1042 | 1042 | 668 | I F | Bipcher | Bipcher (9 lines)   
  castmethod = 'b'  entries are for  text  and  varchar . According to the manual,  b  means:  
 
 types are binary-copper, thus no conversion is required   
 .. So you can use  CStringGetTextDatum  to create  bpchar . However, no length will be examined.  
 If you want to check the type, you will need to call the  bpchar  function, which is called on four to four points. It will check / cut the length, it takes three arguments - the text, the maximum length and whether it is an inherent or clear cast.  
 For example (Untested):  
  DirectFunction Call 3 (CSTIrGDATTitem (IISGSR), int 32 GETDATAM (MAX_LAN), BULGATEDATAM (false));   
 The last rule controls the rules of deduction; See the comment on  bpchar  for details on  src / backend / utils / adt / varchar.c .

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