As a follow-up question, I found some of the varchar column types, in which the histogram_bounds are not being surrounded in double quotes (" ") even in the default implementation. Ex : *c_name* column of *Customer* table
I also found histogram_bounds in which only some strings are surrounded in double quotes and some are not. Ex : *c_address *column of* Customer *table Why are there such inconsistencies? How is this determined? Thank you. On Tue, Jul 8, 2014 at 10:52 AM, Ashoke <s.ash...@gmail.com> wrote: > Hi, > > I am trying to implement a functionality that is similar to ANALYZE, but > needs to have different values (the values will be valid and is stored in > inp->str[][]) for MCV/Histogram Bounds in case the column under > consideration is varchar (C Strings). I have written a function > *dummy_update_attstats* with the following changes. Other things remain > the same as in *update_attstats* of *~/src/backend/commands/analyze.c* > > > *---* > *{* > > * ArrayType *arry; * > * if (* > *strcmp(col_type,"varchar") == 0* > * )* > * arry = construct_array(stats->stavalues[k],* > * stats->numvalues[k], * > * CSTRINGOID,* > * -2, * > * false,* > * 'c'); * > * else* > * arry = construct_array(stats->stavalues[k], * > * stats->numvalues[k],* > * stats->statypid[k], * > * stats->statyplen[k],* > * stats->statypbyval[k], * > * stats->statypalign[k]);* > * values[i++] = PointerGetDatum(arry); /* stavaluesN */ }* > --- > > and I update the hist_values in the appropriate function as: > --- > > *if (strcmp(col_type,"varchar") == 0**)* > * hist_values[i] = datumCopy(CStringGetDatum(inp->str[i][j]),* > * false,* > * -2);* > *---* > > I tried this based on the following reference : > http://www.postgresql.org/message-id/attachment/20352/vacattrstats-extend.diff > > My issue is : When I use my way for strings, the MCV/histogram_bounds in > pg_stats doesn't have double quotes (" ") surrounding string. That is, > > If normal *update_attstats* is used, histogram_bounds for *TPCH > nation(n_name)* are : *"ALGERIA ","ARGENTINA ",...* > If I use *dummy_update_attstats* as above, histogram_bounds for *TPCH > nation(n_name)* are : *ALGERIA,ARGENTINA,...* > > This becomes an issue if the string has ',' (commas), like for example in > *n_comment* column of *nation* table. > > Could someone point out the problem and suggest a solution? > > Thank you. > > -- > Regards, > Ashoke > -- Regards, Ashoke