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create_sql_command

Location

src/bin/pgbench/pgbench.c:5585-5613

Overview

Creates and initializes a Command structure for SQL commands after filtering out comments and whitespace from the input SQL text.

Definition

structure */
	my_command = (Command *) pg_malloc(sizeof(Command));

Detailed Description

The create_sql_command function serves as a constructor for SQL Command structures in pgbench. It takes a buffer containing SQL command text and creates a fully initialized Command object ready for execution. The function first uses skip_sql_comments to remove leading whitespace and comments, returning NULL if no executable content remains. For valid SQL content, it allocates memory for a new Command structure and initializes all its fields with appropriate default values.

The function sets up the command type as SQL_COMMAND, initializes statistics tracking, and prepares the command for parameter parsing and execution. This is a critical component in pgbench's command processing pipeline, bridging the gap between raw script parsing and command execution.

Parameters / Member Variables

  • : PQExpBuffer containing the raw SQL command text collected by the parser
  • : String identifier for the source of the command (filename or builtin-script ID), used for error reporting

Dependencies

  • Functions called/Symbols referenced:
    • skip_sql_comments: Filters out comments and whitespace from SQL text
    • pg_malloc: Allocates memory for the Command structure
    • initPQExpBuffer: Initializes the command's text buffer
    • appendPQExpBufferStr: Copies the cleaned SQL text to the command buffer
    • initSimpleStats: Initializes statistics tracking for the command
    • SQL_COMMAND: Enum value indicating this is an SQL command type
    • META_NONE: Enum value indicating no special metadata handling
  • Called from (representative examples):
    • Script parsing functions that process pgbench input files

Notes and Other Information

  • Returns NULL if the input contains only comments and whitespace, allowing the parser to skip empty commands
  • Allocates memory that must be freed later using appropriate cleanup functions
  • Initializes all Command structure fields to safe default values
  • The first_line field is set to NULL initially and populated later during script processing
  • The prepname field is allocated later if prepared statements are used
  • Statistics tracking is initialized but will be populated during command execution
  • The function assumes the input buffer contains complete, well-formed SQL text from the parser
  • Memory allocation uses pg_malloc which will terminate the program on allocation failure

Simplified Source

static Command *create_sql_command(PQExpBuffer buf, const char *source)
{
    Command *my_command;
    char *p = skip_sql_comments(buf->data);

    // Return NULL if only comments/whitespace
    if (p == NULL)
        return NULL;

    // Allocate and initialize Command structure
    my_command = (Command *) pg_malloc(sizeof(Command));
    initPQExpBuffer(&my_command->lines);
    appendPQExpBufferStr(&my_command->lines, p);

    // Initialize all command fields
    my_command->first_line = NULL;     /* set later */
    my_command->type = SQL_COMMAND;
    my_command->meta = META_NONE;
    my_command->argc = 0;
    my_command->retries = 0;
    my_command->failures = 0;
    memset(my_command->argv, 0, sizeof(my_command->argv));
    my_command->varprefix = NULL;      /* allocated later, if needed */
    my_command->expr = NULL;
    initSimpleStats(&my_command->stats);
    my_command->prepname = NULL;       /* set later, if needed */

    return my_command;
}